Modular isolation reactor support system assemblies and modules

Abstract

The modular reactor isolation support system (MIRSS) assembly includes a cylindrical reactor support structure configured to structurally support a reactor containment system on a seismic isolation device; a collector cylinder configured to at least partially define an uprising annular gap between an inner cylindrical surface of the collector cylinder and an outer sidewall surface of a reactor containment system structurally supported by the cylindrical reactor support structure; a bulkhead configured to at least partially define a downcomer annular gap between an outer cylindrical surface of the bulkhead and the reactor building; and a plurality of exhaust ducts extending from the collector cylinder through the interior of the cylindrical reactor support structure.

Description

[Technical Field]

[0001] government support This invention was made with government support under Contract No. DE-NE0009054 awarded by the U.S. Department of Energy. The government has certain rights in this invention.

[0002] FIELD OF THE INVENTION The exemplary embodiments described herein relate generally to nuclear reactors, and more particularly to providing vibration isolation and integrated passive cooling of nuclear reactors. [Background technology]

[0003] In some nuclear power plants, the nuclear reactor is located within a reactor containment system and a reactor building that structurally supports the reactor containment system on a foundation. The reactor building may include, for example, one or more building structures that house the nuclear reactor and collectively structurally support and contain the reactor containment system.

[0004] In some nuclear power plants, at least a portion (or all) of the reactor building (e.g., the reactor building's upper structure) may be at least partially isolated from seismic forces by one or more isolators, thereby at least partially protecting the reactor containment system and the nuclear reactor contained therein from damage due to earthquake-related phenomena (e.g., earthquakes) at the nuclear power plant. The reactor building structure, which structurally supports the reactor containment system on the one or more isolators, may comprise a reinforced concrete structure. As a result, the structural loads on the isolators from such a building structure may be relatively high. Furthermore, constructing such an isolated structure may include fabricating a reinforcing steel structure, positioning the reinforcing steel structure in place within the reactor building, and then pouring concrete into molds on-site to form the isolated reactor building structure. Such a process may be relatively costly, complex, and time-consuming.

[0005] Additionally, nuclear power plants may include reactor coolant systems that circulate a working fluid (e.g., air) through passageways, conduits, or the like to absorb waste heat from the reactor. In some cases, when the reactor building structure (e.g., the superstructure or the entire reactor building) is seismically isolated by one or more isolators, the reactor coolant system may circulate the working fluid by exhausting it from the reactor containment system through exhaust ducts located below the concrete floor structure of the reactor building. Such concrete floor structures may be relatively thick to provide at least some structural support and containment for the reactor building and / or the reactor containment system, which may reduce cooling at the top of the reactor containment system by vertically spacing the exhaust ducts downward from the top of the reactor containment system. Furthermore, the reactor coolant system exhaust may be included in the reactor building's seismically isolated section, increasing structural loads on the isolators. Summary of the Invention

[0006] According to some embodiments, a nuclear power plant may include a reactor containment system including a nuclear reactor, a reactor building configured to structurally support the reactor containment system on a foundation and to house the reactor containment system within the reactor building, a plurality of seismic isolators coupled to the reactor building, and a modular isolated reactor support system (MIRSS) assembly. The MIRSS assembly may include a cylindrical reactor support structure configured to structurally support the reactor containment system on the plurality of seismic isolators so as to be seismically isolated from the reactor building, where the MIRSS assembly defines a seismic isolation assembly within the nuclear power plant including the reactor containment system. The MIRSS assembly may include a collector cylinder configured to at least partially receive the reactor containment system, the collector cylinder configured to at least partially define a riser annular gap between an inner cylindrical surface of the collector cylinder and an outer sidewall surface of the reactor containment system. The MIRSS assembly may include a bulkhead configured to at least partially define a downcomer annular gap between an outer cylindrical surface of the bulkhead and the reactor building, a bottom opening of the downcomer annular gap in fluid communication with a bottom opening of the riser annular gap. The MIRSS assembly may include a plurality of exhaust ducts extending from the collector cylinder through an interior of the cylindrical reactor support structure.

[0007] The MIRSS assembly may be configured to discharge the working fluid from the isolation assembly by flowing the working fluid downward through the downcomer annular gap to a bottom opening of the downcomer annular gap, from the bottom opening of the downcomer annular gap to a bottom opening of the riser annular gap, through the riser annular gap to a top of the riser annular gap in response to changes in air density due to the working fluid absorbing heat from both the reactor containment system and the collector cylinder, and from the top of the riser annular gap through one or more exhaust ducts of the plurality of exhaust ducts and through the interior of the MIRSS assembly.

[0008] The MIRSS assembly may be configured to couple one or more exhaust ducts to an opening in a non-vibration-isolated exhaust of the reactor coolant system configured to direct the working fluid to the surrounding environment.

[0009] The MIRSS assembly may include a flexible duct coupled between the one or more exhaust ducts and an opening in the non-isolated exhaust portion of the reactor coolant system, the flexible duct being configured to establish fluid communication between the isolated portion of the reactor coolant system and the non-isolated exhaust portion of the reactor coolant system.

[0010] The MIRSS assembly may include an exhaust manifold structure that may at least partially define one or more exhaust ducts and an outlet duct coupled to the one or more exhaust ducts. The outlet duct may be configured to be coupled between the one or more exhaust ducts and the flexible duct.

[0011] The exhaust manifold structure may at least partially define at least two exhaust ducts coupled in parallel with the outlet duct.

[0012] The MIRSS assembly may include a number of MIRSS modules coupled together that collectively define a cylindrical reactor support structure, a collector cylinder, a bulkhead, and a number of exhaust ducts.

[0013] Each MIRSS module of the plurality of MIRSS modules may define a distinct azimuthal segment of the cylindrical reactor support structure, a distinct azimuthal segment of the collector cylinder, and a distinct azimuthal segment of the bulkhead.

[0014] The plurality of MIRSS modules may include a plurality of upper modular structures collectively defining a cylindrical reactor support structure and a plurality of lower modular structures axially stacked below the plurality of upper modular structures. The plurality of lower modular structures may be stacked to collectively define a bulkhead. The plurality of upper modular structures and the plurality of lower modular structures may collectively define a collector cylinder.

[0015] At least one upper modular structure of the plurality of upper modular structures may at least partially define one or more exhaust ducts.

[0016] The MIRSS assembly may be configured to define at least one shielded chamber within the MIRSS assembly and radially outward from the collector cylinder, the at least one shielded chamber configured to hold at least one shielding material.

[0017] The MIRSS assembly may be configured to direct the working fluid to the downcomer annular gap via a heat transfer path that passes through at least one isolator of the plurality of isolators, thereby causing the working fluid to remove heat from the at least one isolator by the MIRSS assembly.

[0018] The nuclear power plant may further comprise a heater configured to heat the at least one isolator.

[0019] The plurality of isolators may be at least partially insulated from the working fluid directed into the downcomer annular gap.

[0020] The isolation assembly may define a floor structure of a head access area (HAA) housed above the floor structure by an upper building structure of the reactor building, thereby isolating the floor structure from the upper building structure that houses the HAA above the floor structure. The MIRSS assembly may further include an HAA seal configured to establish a seal between the floor structure and the upper building structure.

[0021] According to some example embodiments, a modular reactor isolation support system (MIRSS) module configured to define an azimuthal portion of an annular structure may include an upper modular structure defining a distinct azimuthal segment of a cylindrical reactor support structure of the annular structure, the upper modular structure being configured to structurally support at least a portion of the structural load of a reactor containment system including the nuclear reactor. The MIRSS module may include one or more lower modular structures axially stacked below the upper modular structure, the one or more lower modular structures collectively defining a distinct azimuthal segment of a bulkhead of the annular structure. The upper modular structure and the one or more lower modular structures may have respective inner sidewall surfaces that collectively define a distinct azimuthal segment of a collector cylinder of the annular structure.

[0022] The upper modular structure may be configured to at least partially define a shielded chamber within a module of the upper modular structure, and the upper modular structure may be configured to retain shielding material within the shielded chamber.

[0023] The upper modular structure may be configured to at least partially define one or more exhaust ducts extending from separate azimuthal segments of the collector cylinder through the module interior of the upper modular structure.

[0024] According to some example embodiments, a MIRSS assembly may include a plurality of MIRSS modules, each of which may be a MIRSS module described above. The plurality of MIRSS modules may be azimuthally coupled to collectively define an annular structure, such that the MIRSS assembly may include an annular cylindrical reactor support structure, an annular collector cylinder, an annular bulkhead, and a plurality of exhaust ducts extending from the collector cylinder through an interior of the cylindrical reactor support structure.

[0025] The MIRSS assembly may be configured to discharge the working fluid from the MIRSS assembly by flowing the working fluid downward through the downcomer annular gap to a bottom opening of the downcomer annular gap, from the bottom opening of the downcomer annular gap to a bottom opening of the riser annular gap, through the riser annular gap to a top of the riser annular gap in response to changes in air density due to the working fluid absorbing heat from both the protective vessel and the collector cylinder, and from the top of the riser annular gap through one or more exhaust ducts of the plurality of exhaust ducts and through the interior of the MIRSS assembly.

[0026] The MIRSS assembly may be configured to couple one or more exhaust ducts to an opening in a non-vibration-isolated exhaust of the reactor coolant system configured to direct the working fluid to the surrounding environment.

[0027] The MIRSS assembly may include a flexible duct coupled between one or more exhaust ducts and an opening in a non-isolated exhaust portion of the reactor cooling system, the flexible duct configured to establish fluid communication between the isolated portion of the reactor cooling system and the non-isolated exhaust portion of the reactor cooling system.

[0028] The MIRSS assembly may include an exhaust manifold structure that may at least partially define one or more exhaust ducts and an outlet duct coupled to the one or more exhaust ducts. The outlet duct may be configured to be coupled between the one or more exhaust ducts and the flexible duct.

[0029] The exhaust manifold structure may at least partially define at least two exhaust ducts coupled in parallel with the outlet duct.

[0030] In some example embodiments, a method of constructing a nuclear power plant may include constructing a reactor building lower building structure configured to structurally support and contain a reactor containment system configured to include a nuclear reactor, the lower building structure including at least one reactor building support surface configured to support structural loads of the reactor containment system on a foundation; mounting a plurality of seismic isolators on the at least one reactor building support surface; constructing a modular reactor isolation support system (MIRSS) assembly; mounting the MIRSS assembly on the plurality of seismic isolators such that the MIRSS assembly defines a seismic isolation assembly within the nuclear power plant; and mounting the reactor containment system on the MIRSS assembly such that the MIRSS assembly structurally supports the reactor containment system on the plurality of seismic isolators such that the seismic isolation assembly includes the reactor containment system. The MIRSS assembly may include: a cylindrical reactor support structure configured to structurally support the reactor containment system on a plurality of seismic isolation devices so that the MIRSS assembly collectively defines a seismic isolation assembly within a nuclear power plant including the reactor containment system and is seismically isolated from the reactor building; a collector cylinder configured to at least partially receive the reactor containment system based on the reactor containment system being structurally supported by the cylindrical reactor support structure, the collector cylinder configured to at least partially define an uprising annular gap between an inner cylindrical surface of the collector cylinder and an outer sidewall surface of the reactor containment system; a bulkhead configured to at least partially define a downcomer annular gap between an outer cylindrical surface of the bulkhead and the reactor building; and a plurality of exhaust ducts extending from the collector cylinder through the interior of the cylindrical reactor support structure.

[0031] The method may further include completing the reactor building by constructing an upper building structure of the reactor building on the lower building structure and housing the reactor containment system within the reactor building. The isolation assembly may be seismically isolated from the lower building structure and the upper building structure such that the isolation assembly defines a floor structure of a head access area (HAA) housed above the floor structure by the upper building structure of the reactor building, and the floor structure is seismically isolated from the upper building structure housing the HAA above the floor structure, and the MIRSS assembly may further include an HAA seal configured to establish a seal between the floor structure and the upper building structure.

[0032] The lower building structure may include a storage pit configured to at least partially receive the reactor containment system. The at least one reactor building support surface at least partially surrounds the storage pit at a top opening of the storage pit such that a plurality of seismic isolators are mounted on the at least one reactor building support surface and extend in a circumferential pattern at least around the top opening of the storage pit. Mounting the MIRSS assembly on the plurality of seismic isolators may include lowering the MIRSS assembly at least partially into the storage pit such that the MIRSS assembly is structurally supported on the plurality of seismic isolators and extends downwardly through the top opening of the storage pit at least partially into the storage pit, the MIRSS assembly being configured to structurally support the reactor containment system within the collector cylinder and extend downwardly at least partially into the storage pit.

[0033] The MIRSS assembly may be configured to define at least one shielded chamber within the MIRSS assembly and radially outward from the collector cylinder, the at least one shielded chamber configured to hold at least one shielding material.

[0034] Construction of a MIRSS assembly may include joining together multiple MIRSS modules to collectively define a cylindrical reactor support structure, a collector cylinder, a bulkhead, and multiple exhaust ducts.

[0035] Each MIRSS module of the plurality of MIRSS modules may define a separate azimuthal segment of the cylindrical reactor support structure, a separate azimuthal segment of the collector cylinder, and a separate azimuthal segment of the bulkhead, such that construction of the MIRSS assembly includes azimuthal coupling of the plurality of MIRSS modules together.

[0036] The method may further include fabricating a plurality of MIRSS modules at one or more remote locations and transporting the plurality of MIRSS modules from the one or more remote locations to the underlying building structure prior to connecting the plurality of MIRSS modules together.

[0037] The method may further include coupling a plurality of exhaust ducts of the MIRSS assembly to an opening in a non-vibration-isolated exhaust of the reactor coolant system in fluid communication with the surrounding environment.

[0038] Connecting the plurality of exhaust ducts to the non-isolated exhaust section may include connecting a flexible duct between one or more of the plurality of exhaust ducts and an opening of the non-isolated exhaust section of the reactor cooling system, such that the flexible duct establishes fluid communication between the isolation section of the reactor cooling system and the non-isolated exhaust section.

[0039] The method may further include coupling the exhaust manifold structure to the cylindrical reactor support structure such that at least a portion of the exhaust manifold structure extends through the cylindrical reactor support structure to the collector cylinder to at least partially define one or more exhaust ducts. The method may further include coupling the exhaust ducts of the exhaust manifold structure to the flexible duct. [Brief explanation of the drawings]

[0040] Various features and advantages of the non-limiting embodiments herein may become more apparent from a consideration of the detailed description in conjunction with the accompanying drawings. The accompanying drawings are provided for illustrative purposes only and should not be construed as limiting the scope of the claims. The accompanying drawings should not be considered as drawn to scale unless expressly stated. Various dimensions of the drawings may be exaggerated for clarity.

[0041] [Figure 1A] FIG. 1A is a perspective view of a nuclear power plant including a reactor building housing a reactor containment system and a MIRSS assembly, according to some example embodiments. [Figure 1B] FIG. 1B is a cross-sectional perspective view of the nuclear power plant of FIG. 1A taken along cross-sectional line IB-IB′ of FIG. 1A, according to some example embodiments. [Figure 1C] FIG. 1C is a cross-sectional plan view of the nuclear power plant of FIG. 1A along cross-sectional line IC-IC' of FIG. 1B, according to some example embodiments. [Figure 1D] FIG. 1D is a cross-sectional plan view of the nuclear power plant of FIG. 1A along cross-sectional line ID-ID′ of FIG. 1B, according to some example embodiments. [Figure 1E] FIG. 1E is a cross-sectional plan view of the nuclear power plant of FIG. 1A along cross-sectional line IE-IE′ of FIG. 1B, according to some example embodiments. [Figure 1F] FIG. 1F is a cross-sectional elevation view of the nuclear power plant of FIG. 1A along cross-sectional line IF-IF' of FIG. 1C, according to some example embodiments. [Figure 1G] FIG. 1G is a cross-sectional elevation view of the nuclear power plant of FIG. 1A along cross-sectional line IG-IG' of FIG. 1C, according to some example embodiments. [Figure 1H] FIG. 1H is a cross-sectional elevation view of region X of the nuclear power plant of FIG. 1G, according to some example embodiments. [Figure 2A] FIG. 2A is a perspective view of a MIRSS assembly, according to some exemplary embodiments. [Figure 2B]FIG. 2B is an elevational view of the MIRSS assembly of FIG. 2A, according to some exemplary embodiments. [Figure 2C] FIG. 2C is an elevational view of the MIRSS assembly of FIG. 2A, according to some exemplary embodiments. [Figure 2D] FIG. 2D is a cross-sectional plan view of the MIRSS assembly of FIG. 2A along cross-sectional line IID-IID′ of FIG. 2B, according to some exemplary embodiments. [Figure 2E] 2E is a cross-sectional plan view of the MIRSS assembly of FIG. 2A taken along cross-sectional line IIE-IIE′ of FIG. 2B, according to some exemplary embodiments. [Figure 2F] 2F is a cross-sectional elevation view of the MIRSS assembly of FIG. 2A taken along cross-sectional line IIF-IIF′ of FIG. 2A, according to some exemplary embodiments. [Figure 2G] FIG. 2G is a perspective cross-sectional view of the MIRSS assembly of FIG. 2A on multiple isolators, according to some exemplary embodiments. [Figure 3A] FIG. 3A is a perspective view of a MIRSS module, according to some exemplary embodiments. [Figure 3B] FIG. 3B is a perspective view of a MIRSS module, according to some exemplary embodiments. [Figure 3C] 3C is a cross-sectional elevation view of the MIRSS module of FIG. 3A taken along cross-sectional line IIIC-IIIC' of FIG. 3A, according to some exemplary embodiments. [Figure 3D] 3D is a cross-sectional elevation view of the MIRSS module of FIG. 3A along cross-sectional line IIID-IIID' of FIG. 3C, according to some exemplary embodiments. [Figure 3E] FIG. 3E is a cross-sectional plan view of the MIRSS module of FIG. 3A taken along cross-sectional line IIIE-IIIE′ of FIG. 3D, according to some exemplary embodiments. [Figure 3F] 3F is a cross-sectional plan view of the MIRSS module of FIG. 3A taken along cross-sectional line IIIF-IIIF' of FIG. 3D, according to some exemplary embodiments. [Figure 4A]FIG. 4A is a perspective view of a MIRSS module, according to some exemplary embodiments. [Figure 4B] FIG. 4B is a perspective view of a MIRSS module, according to some exemplary embodiments. [Figure 4C] 4C is a cross-sectional elevation view of the MIRSS module of FIG. 4A along cross-sectional line IVC-IVC′ of FIG. 4A, according to some exemplary embodiments. [Figure 4D] 4D is a cross-sectional elevation view of the MIRSS module of FIG. 4A along cross-sectional line IVD-IVD' of FIG. 4C, according to some exemplary embodiments. [Figure 5A] FIG. 5A is a perspective view of a MIRSS module, according to some exemplary embodiments. [Figure 5B] FIG. 5B is a perspective view of a MIRSS module, according to some exemplary embodiments. [Figure 5C] 5C is a cross-sectional elevation view of the MIRSS module of FIG. 5A taken along cross-sectional line VC-VC' of FIG. 5A, according to some exemplary embodiments. [Figure 5D] 5D is a cross-sectional elevation view of the MIRSS module of FIG. 5A along cross-sectional line VD-VD' of FIG. 5C, according to some exemplary embodiments. [Figure 6A] FIG. 6A is a perspective view of a MIRSS exhaust manifold structure, according to some exemplary embodiments. [Figure 6B] FIG. 6B is a perspective view of a MIRSS exhaust manifold structure, according to some exemplary embodiments. [Figure 6C] 6C is a cross-sectional perspective view of the MIRSS exhaust manifold structure of FIG. 6A taken along cross-sectional line VIC-VIC′ of FIG. 6A, according to some exemplary embodiments. [Figure 7A] FIG. 7A is a perspective view of a MIRSS module, according to some exemplary embodiments. [Figure 7B] FIG. 7B is a perspective view of a MIRSS module, according to some exemplary embodiments. [Figure 7C]7C is a cross-sectional elevation view of the MIRSS module of FIG. 7A taken along cross-sectional line VIIC-VIIC' of FIG. 7B, according to some exemplary embodiments. [Figure 8A] FIG. 8A is a perspective view of a MIRSS assembly, according to some exemplary embodiments. [Figure 8B] 8B is a cross-sectional perspective view of the MIRSS assembly of FIG. 8A taken along cross-sectional line VIIIB-VIIIB' of FIG. 8A, according to some exemplary embodiments. [Figure 9A] FIG. 9A is a perspective view of a nuclear reactor building including the MIRSS assembly of FIG. 8A, according to some example embodiments. [Figure 9B] 9B is a cross-sectional elevation view of the reactor building of FIG. 9A taken along cross-sectional line IXB-IXB' of FIG. 9A, according to some example embodiments. [Figure 9C] 9C is a cross-sectional elevation view of the reactor building of FIG. 9A taken along cross-sectional line IXC-IXC' of FIG. 9A, according to some example embodiments. [Figure 9D] 9D is a top cross-sectional plan view of the nuclear reactor building of FIG. 9A taken along cross-sectional line IXD-IXD' of FIG. 9C, according to some example embodiments. [Figure 9E] 9E is a top cross-sectional plan view of the reactor building of FIG. 9A taken along cross-sectional line IXE-IXE′ of FIG. 9C, according to some example embodiments. [Figure 10A] FIG. 10A is a perspective view of a nuclear reactor building including the MIRSS assembly of FIG. 8A, according to some example embodiments. [Figure 10B] 10B is a cross-sectional elevation view of the reactor building of FIG. 10A along cross-sectional line XB-XB' of FIG. 10A, according to some example embodiments. [Figure 10C] 10C is a top cross-sectional plan view of the nuclear reactor building of FIG. 10A taken along cross-sectional line XC-XC' of FIG. 10B, according to some embodiments. [Figure 10D]10D is a top cross-sectional plan view of the nuclear reactor building of FIG. 10A taken along cross-sectional line XD-XD' of FIG. 10B, according to some example embodiments. [Figure 11] FIG. 11 is a flowchart illustrating a method for constructing a nuclear power plant, according to some example embodiments. DETAILED DESCRIPTION OF THE INVENTION

[0042] When an element or layer is referred to as being "on," "connected," "coupled to," or "covering" another element or layer, it is directly on, connected to, coupled to, or covering the other element or layer, or there may be intervening elements or layers. Conversely, when an element is referred to as being "directly on," "directly connected to," or "directly coupled to" another element or layer, there are no intervening elements or layers. Like numbers refer to like elements throughout the specification. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0043] Although terms such as "first," "second," and "third" are used herein to describe various elements, components, regions, layers, and / or sections, these elements, components, regions, layers, and / or sections should not be limited by these terms. These terms are used only to distinguish one element, component, region, layer, or section from another region, layer, or section. Thus, a first element, component, region, layer, or section discussed below could be referred to as a second element, component, region, layer, or section without departing from the teachings of the exemplary embodiments.

[0044] Spatially relative terms (e.g., "lower," "below," "lower side," "upper," "upper," etc.) may be used herein to facilitate describing the relationship of one element or feature to other elements or features as shown in the figures. It should be understood that spatially relative terms are intended to encompass other orientations of the device during use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures were turned over, an element described as "below" or "lower" of other elements or features would now be oriented "above" the other elements or features. Thus, the term "lower" can encompass both an orientation of "upper" and "lower." The device may also be otherwise oriented (rotated 90 degrees or at other orientations), and the spatially relative descriptors used herein interpreted accordingly.

[0045] The terminology used herein is for the purpose of describing various embodiments only and is not intended to limit example embodiments. As used herein, the singular articles "a," "an," and "the" are intended to include the plural forms unless the context clearly indicates otherwise. The terms "comprise," "including," "comprises," and / or "comprising," when used herein, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0046] The exemplary embodiments are described herein with reference to cross-sectional diagrams that are schematic illustrations of idealized embodiments (and intermediate structures) of the exemplary embodiments. As such, variations in the shapes depicted are expected as a result, for example, of manufacturing techniques and / or tolerances. Accordingly, the exemplary embodiments should not be construed as limited to the shapes of regions depicted herein and may include shape variations that result, for example, from manufacturing. For example, an implanted region depicted as a rectangle will typically have rounded or curved features and / or gradients in implant concentration at its edges, rather than a binary transition from implanted to non-implanted region. Similarly, a buried region formed by implantation may result in some implantation in a region between the buried region and the surface where the implantation occurs. Therefore, the regions depicted in the figures are schematic in nature, and their shapes are not intended to represent the actual shape of a region of a device, nor are they intended to limit the scope of the exemplary embodiments.

[0047] Exemplary embodiments may be described with reference to acts and symbolic representations (e.g., in the form of flowcharts, flow diagrams, data flow diagrams, structure diagrams, block diagrams, etc.) of operations that may be implemented in conjunction with units and / or devices discussed in more detail below. Although discussed in a particular manner, the functions or operations identified in a particular block may be implemented differently from the flow identified in the flowchart, flow diagram, etc. For example, functions or operations illustrated as being performed in series in two consecutive blocks may in fact be performed concurrently, or may even be performed in the reverse order.

[0048] Unless otherwise specified, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the exemplary embodiments belong. Terms, including terms defined in commonly used dictionaries, should be interpreted as having a meaning consistent with the meaning in the context of the relevant art, and not in an idealized or overly formal sense, unless otherwise expressly stated herein.

[0049] Although the description is given with reference to specific examples and figures, various modifications, additions, and substitutions of the exemplary embodiments may be made in response to the description by those skilled in the art. For example, the techniques described may be performed in an order different from that described, and / or the components of the described systems, architectures, devices, circuits, etc. may be connected or combined differently from that described, or the results may be substantially achieved by other components or equivalents.

[0050] It will be understood that "coolant fluid" as used herein may include any known coolant fluid that may be used to cool any portion of a nuclear power plant and / or reactor, including water, a liquid metal (e.g., liquid sodium), a gas (e.g., helium), a molten salt, or any combination thereof. It will be understood that "fluid" as used herein may include a gas, a liquid, or any combination thereof.

[0051] The inventive concept relates to a unique reactor support system, also referred to herein as a reactor support assembly. The reactor support assembly is configured to control reactor movement due to significant earthquake-related events, thereby improving seismic protection of the reactor and the reactor containment system containing the reactor. The reactor support assembly further enables a practical approach to the design and construction of nuclear power plants, enabling increased construction efficiency and improving the cost of fabricating and constructing nuclear power plant structures, due to the reactor support assembly's modularity, simplicity, and cost-effectiveness. The reactor support assembly may comprise a modular isolated reactor support system (MIRSS) assembly consisting of multiple structures (e.g., multiple MIRSS modules) at least partially connected together, or a non-modular isolated reactor support system (IRSS) at least partially assembled as a single structure without connecting prefabricated modules together. It will be understood that while the description herein may refer to a MIRSS assembly for simplicity, a "MIRSS assembly" or "Modular Isolation Reactor Support System (MIRSS)" as described herein may be any reactor support assembly according to any of the exemplary embodiments, including either a Modular Isolation Reactor Support System (MIRSS) assembly made up of multiple structures (e.g., multiple MIRSS modules) at least partially connected together, or a Non-Modular Isolation Reactor Support System (IRSSS) made up of prefabricated modules at least partially assembled as a single structure without being connected together.

[0052] The MIRSS assembly includes a support structure, collectively referred to herein as an annular structure, a cylindrical support structure, etc., configured to be seismically isolated from the reactor building by being mounted on and structurally supported by seismic isolators. The structure comprising the MIRSS assembly may include and / or at least partially define one or more of a cylindrical reactor support structure, a Reactor Containment System Auxiliary Cooling System (RVACS) bulkhead (also referred to herein as a bulkhead), a RVACS collector cylinder (also referred to herein as a collector cylinder), a RVACS inlet annular gap to head access area seals, also referred to herein as HAA seals, one or more shielded chambers configured to house one or more shielding materials configured to provide radiation and / or thermal shielding, any combination thereof, etc. It will be appreciated that in some example embodiments, a structure comprising a MIRSS assembly may include a plurality of exhaust ducts extending from the collector cylinder through the cylindrical reactor support structure, for example, extending from the inner cylindrical surface of the collector cylinder to an outer sidewall surface of the MIRSS assembly opposite the inner cylindrical surface of the collector cylinder, and configured to direct the working fluid to exit the collector cylinder and further exit the MIRSS assembly. The exhaust ducts may be defined by structural members of the cylindrical reactor support structure and / or by duct structure of a separate exhaust manifold structure that may be coupled to the cylindrical reactor support structure, although example embodiments are not limited thereto. Once assembled, the various structures comprising and / or implemented by the MIRSS assembly may be configured to function as a unit (e.g., as a single-piece structure) under normal conditions and seismic conditions (e.g., during an earthquake).

[0053] FIG. 1A is a perspective view of a nuclear power plant 100 including a reactor building 102 housing a reactor containment system 140 and a MIRSS assembly 200, according to some illustrative embodiments. FIG. 1B is a cross-sectional perspective view of the reactor building 102, MIRSS assembly 200, and reactor containment system 140 of FIG. 1A along cross-sectional line IB-IB' of FIG. 1A, according to some illustrative embodiments. FIG. 1C is a cross-sectional plan view of the nuclear power plant 100 of FIG. 1A along cross-sectional line IC-IC' of FIG. 1B, according to some illustrative embodiments. FIG. 1D is a cross-sectional plan view of the nuclear power plant 100 of FIG. 1A along cross-sectional line ID-ID' of FIG. 1B, according to some illustrative embodiments. FIG. 1E is a cross-sectional plan view of the nuclear power plant 100 of FIG. 1A along cross-sectional line IE-IE' of FIG. 1B, according to some illustrative embodiments. FIG. 1F is a cross-sectional elevation view of the nuclear power plant 100 of FIG. 1A along cross-sectional line IF-IF' of FIG. 1C, according to some illustrative embodiments. Figure 1G is a cross-sectional elevation view of the nuclear power plant 100 of Figure 1A along section line IG-IG' of Figure 1C, according to some illustrative embodiments. Figure 1H is a cross-sectional elevation view of region X of the nuclear power plant 100 of Figure 1G, according to some illustrative embodiments.

[0054] FIG. 2A is a perspective view of a MIRSS assembly 200, according to some exemplary embodiments. FIGS. 2B and 2C are elevation views of the MIRSS assembly 200 of FIG. 2A, according to some exemplary embodiments. FIG. 2D is a cross-sectional plan view of the MIRSS assembly 200 of FIG. 2A taken along section line IID-IID' of FIG. 2B, according to some exemplary embodiments. FIG. 2E is a cross-sectional plan view of the MIRSS assembly 200 of FIG. 2A taken along section line IIE-IIE' of FIG. 2B, according to some exemplary embodiments. FIG. 2F is a cross-sectional elevation view of the MIRSS assembly 200 of FIG. 2A taken along section line IIF-IIF' of FIG. 2A, according to some exemplary embodiments. FIG. 2G is a perspective cross-sectional view of the MIRSS assembly 200 of FIG. 2A over multiple isolators, according to some exemplary embodiments.

[0055] 1A-1H, a nuclear power plant 100 (also referred to herein as a nuclear power plant) may include a reactor containment system 140, a reactor building 102 configured to structurally support the reactor containment system 140 on a foundation and to house the reactor containment system 140 within an interior 108 of the reactor building 102, and a MIRSS assembly 200 configured to structurally support the reactor containment system 140 on a seismic isolator 150 coupled to the reactor building 102 such that the MIRSSS assembly 200 structurally supports and seismically isolates the reactor containment system 140 from the reactor building 102.

[0056] In some exemplary embodiments, as shown in at least FIGS. 1B and 1F-1H, the reactor containment system 140 may include a protective vessel 144 (GV), a primary vessel 146 (e.g., reactor vessel), and a head 148 (e.g., reactor head, reactor vessel head, head assembly, head structure, head plate, cap, etc.), and may further be understood to include the reactor 142. The protective vessel 144 and the head 148 may collectively define a containment section in which the primary vessel 146 and the reactor 142 are disposed. The reactor containment system 140 may also be referred to as a reactor module. The reactor containment system 140 is configured to contain (e.g., structurally support and contain) the reactor 142. The primary vessel 146 is configured to contain the reactor 142 and may be configured to contain one or more working fluids (e.g., liquid metal, water, gas, etc.) that circulate through a heat transfer path that passes through the reactor 142. The protective vessel 144 may be configured to isolate the primary vessel 146 to reduce, minimize, or prevent leakage of one or more coolant fluid materials (e.g., liquid metal, water, gas, etc.) from the primary vessel 146 into the reactor building 102 and / or the external environment. It will be understood that the nuclear reactor 142 described herein may include or be referred to as a reactor core. It will be understood that the nuclear reactor 142 described herein may include any type of nuclear reactor, including, but not limited to, a boiling water reactor (BWR), a pressurized water reactor (PWR), a liquid metal-cooled reactor, a molten salt reactor (MSR), an advanced boiling water reactor (ABWR), an economical simplified boiling water reactor (ESBWR), a BWRX-300 reactor, etc. The reactor containment system 140 may be configured to retain the primary vessel 146 within the protective vessel 144 to define an annular gap space between an outer sidewall of the primary vessel 146 and an inner sidewall of the protective vessel 144. The reactor containment system 140 may be configured to reduce, minimize, or prevent closure of the annular gap between the primary vessel 146 and the protective vessel 144 due to seismic movement of the reactor containment system 140 relative to the reactor building 102 by maintaining a fixed relative position of the primary vessel 146 and the protective vessel 144, thereby reducing, minimizing, or preventing relative movement of the primary vessel 146 and the protective vessel 144.It will be appreciated that reactor containment system 140 is not limited to exemplary embodiments including each of reactor 142, primary vessel 146, head 148, and protective vessel. For example, in some exemplary embodiments, reactor containment system 140 may not include (e.g., may be omitted from) protective vessel 144, and outer sidewall 140-S of reactor containment system 140 may be the outer sidewall of primary vessel 146.

[0057] The reactor building 102 may comprise a lower building structure 102-1 and an upper building structure 102-2. The lower building structure 102-1 may be configured to structurally support at least the reactor containment system 140 and a supporting structure (e.g., the MIRSS assembly 200) on a foundation 170 that rests on the underlying soil 180. In some exemplary embodiments, the foundation 170 may be included as part of the lower building structure 102-1. In some exemplary embodiments, the lower building structure 102-1 and the foundation 170 may be separate structures, with the lower building structure 102-1 structurally supported by the foundation 170. The upper building structure 102-2 may at least partially complete the containment of the interior 108 of the reactor building 102, including a reactor head access area (HAA) 292 above the reactor containment system 140.

[0058] 1A-1H, the lower building structure 102-1 may include a containment pit 102-11 that may extend at least partially below the grade 182 of the underlying soil 180 and may have a top opening 102-11O and an inner containment pit surface 102-11S that defines a cylindrical volume therein. However, example embodiments are not limited in this regard, and it will be understood that in some example embodiments, the seismic isolator 150 may structurally support the MIRSS assembly 200 and the reactor containment system 140 on the structural support surface 102-12, generally above the seismic isolator 150. When an element is structurally supported by or on other elements, the other elements are configured to support some or all (e.g., all) of the structural load (e.g., some or all of the weight) of the element and to transfer such structural load to an underlying element or structure (e.g., foundation 170) on which the other element rests, such that the "structurally supported" element may be understood to rest on structural supporting elements.

[0059] As shown in at least FIG. 1D , the isolator 150 may be arranged in a circumferential pattern about a central axis that may be paraxial or coaxial with the central axis of the MIRSS assembly 200 mounted on the isolator 150. For example, as shown, if the lower building structure 102-1 includes a storage pit 102-11, the isolator 150 may be arranged in a circumferential pattern at least partially around the top opening 102-11O of the storage pit 102-11. As shown, the circumferential pattern along which the isolator 150 is arranged may be a circular pattern, although exemplary embodiments are not limited thereto. For example, the circumferential pattern may be a polygonal pattern having any polygonal shape, including a square pattern, a rectangular pattern, a nonagonal pattern, a decagonal pattern, etc. In other examples, the circumferential pattern may be a pattern having any non-polygonal or non-circular shape, including, for example, an oval pattern or an elliptical pattern.

[0060] 1A-1H , the nuclear power plant 100 may include a reactor cooling system 130, which may be a reactor vessel auxiliary cooling system (RVACS). The reactor cooling system 130 may be configured to circulate a working fluid through one or more circuits 236 to remove heat from the reactor building 102. The reactor cooling system 130 may be configured to draw a working fluid 240 (e.g., air) from the surrounding environment 123 and circulate it through one or more circuits 236 extending through the reactor building 102 and through one or more portions of the MIRSS assembly 200 to absorb heat from at least the reactor containment system 140, and to expel the working fluid 240 from the reactor building to remove the absorbed heat from the reactor building 102. By circulating such working fluid 240, the reactor cooling system 130 may remove residual heat from the reactor containment system 140. By circulating such working fluid 240, the reactor cooling system 130 may provide supplemental cooling of the reactor containment system 140 in addition to a separate main coolant loop (not shown) that may circulate a coolant (e.g., liquid metal coolant, water coolant, etc.) within the reactor containment system 140 to remove heat from the reactor 142. By circulating such working fluid 240, the reactor cooling system 130 may provide supplemental and / or emergency cooling of the reactor 142, primary vessel 146, protective vessel 144, reactor containment system 140, etc., in emergency conditions. It will be understood that one or more circuits 236 include and / or are defined by the conduits and passages of the reactor cooling system 130 that collectively extend from the intake system 112 to the exhaust system 122 through the riser annulus 224 and through which the working fluid 240 circulates to at least remove heat from the reactor containment system 140.While the working fluid 240 is illustrated as being circulated from the surrounding environment 123 and the working fluid 240 may be air, it will be understood that exemplary embodiments are not limited thereto and that in some exemplary embodiments the working fluid 240 may be any suitable heat transfer fluid (e.g., liquid, gas, etc.) and the surrounding environment 123 may be a reservoir and / or heat sink structure configured to act as a heat sink for the working fluid.

[0061] In some exemplary embodiments, reactor cooling system 130 is configured to define various reactor cooling system circuits 236 through which working fluid 240 is circulated to form a "natural" or "density-driven" working fluid circulation through reactor cooling system 130, such that circulation of working fluid through reactor cooling system 130 can be maintained without operation of working fluid-moving machinery and / or force-induced machinery (e.g., mechanical movement machinery, blowers, etc.). For example, with further reference to FIGS. 1A-1H , reactor cooling system 130 can include downcomer annulus 214 configured to direct working fluid 240 to draw working fluid 240 from surrounding environment 123 and flow vertically downward, through downcomer annulus 214, and at least partially through bottom opening 214-B of downcomer annulus 214 to a location axially lower in reactor containment system 140. The reactor cooling system 130 may further include a riser annular gap 224 positioned concentric (e.g., coaxial) with and radially inward from the downcomer annular gap 214 around the reactor containment system 140, the riser annular gap 224 being defined at least in part by the outer sidewall surface 140-S of the reactor containment system 140, with bottom openings 214-B and 224-B of the downcomer annular gap 214 and the riser annular gap 224, respectively, being in fluid communication with each other (via an air sink 234 positioned below and open toward both the downcomer annular gap 214 and the riser annular gap 224). As described herein, the fluidly connected bottom opening 214-B of downcomer annular gap 214 and the bottom opening 224-B of riser annular gap 224 are part of a common (identical) open flow path, thereby allowing working fluid 240 to freely flow from downcomer annular gap 214 to riser annular gap 224 through their respective bottom openings 214-B and 224-B. As described herein, the bottom opening 214-B of downcomer annular gap 214 is also referred to as a downcomer annular gap outlet, and the bottom opening 224-B of riser annular gap 224 is also referred to as a riser annular gap inlet.The reactor cooling system 130 may be configured to direct the working fluid 240 to flow from the bottom opening 214-B of the downcomer annular gap 214 and upward through the bottom 224-B of the riser annular gap 224 to absorb heat within the riser annular gap 224.

[0062] In some exemplary embodiments, the collector cylinder 210 may absorb heat radiated from the reactor containment system 140 (e.g., via radiative heat transfer from the primary vessel 146 to the collector cylinder 210). It will be understood that the heat transfer to the collector cylinder 210 may not include any convective heat transfer through the working fluid 240 from the reactor containment system 140 (e.g., the protective vessel 144) to the collector cylinder 210, because the radiative heat transfer from the reactor containment system 140 to the collector cylinder 210 may establish a temperature gradient directed from the collector cylinder 210 to the working fluid 240. Thus, in addition to the reactor containment system 140 (e.g., the outer sidewall surface 140-S of the reactor containment system 140) serving as a heat transfer surface to the working fluid 240 in the riser annular gap 224, the collector cylinder 210 may be configured to serve as a heat transfer surface for heat transfer to the working fluid 240 in the riser annular gap 224 (e.g., the inner cylindrical surface 212 of the collector cylinder 210 may serve as a convective heat transfer surface), thereby increasing the collective heat transfer surface within the riser annular gap 224 and facilitating improved heat transfer to the working fluid 240. As a result, in some exemplary embodiments, the working fluid 240 in the riser annular gap 224 may absorb heat (e.g., via convective heat transfer) from the reactor containment system 140 (e.g., from the protective vessel 144) via the outer sidewall surface 140-S of the reactor containment system 140, which at least partially defines the inner diameter of the riser annular gap 224 (e.g., via the outer sidewall surface 144-S of the protective vessel 144), as well as from the collector cylinder 210 (e.g., via the inner cylindrical surface 212, which at least partially defines the outer diameter of the riser annular gap 224).

[0063] The working fluid 240 received within the reactor coolant system 130 from the ambient environment 123 and directed through the downcomer annular gap 214 to at least the bottom opening 214-B of the downcomer annular gap 214 is identified herein as cold working fluid 242, which is also referred to herein as intake air, cold air, atmospheric air, intake working fluid, ambient working fluid, etc. The working fluid 240 that has absorbed heat within the riser annular gap 224 (e.g., from the reactor containment system 140 and from the collector cylinder 210) is identified herein as hot working fluid 244, which is also referred to herein as exhaust air, hot air, heated air, exhaust working fluid, heated working fluid, etc. The working fluid 240 (e.g., hot working fluid 244) that has absorbed heat within the riser annular gap 224 may "rise" upward through the riser annular gap 224 to the top 224-U of the riser annular gap 224 (also referred to as the top region of the riser annular gap 224) and toward one or more conduits (e.g., one or more exhaust ducts 216) in fluid communication between the top 224-U of the riser annular gap 224 and the surrounding environment 123 in response to a change in air density due to the working fluid 240 absorbing heat within the riser annular gap 224. The hot working fluid 224 may "rise" to exit the reactor coolant system 130 via the one or more exhaust ducts 216 due to a decrease in density of the heated hot working fluid 244 associated with the cooler working fluid 240 entering the bottom opening 224-B of the riser annular gap 224 (e.g., cold working fluid 242).

[0064] The vertical upward flow of working fluid 240 exiting riser annular gap 224 through top 224-U of riser annular gap 224 and through one or more exhaust ducts 216 toward the surrounding environment 123 may be induced by additional cold working fluid 242 being drawn into the bottom of riser annular gap 224 and / or may cause this additional cold working fluid 242 to displace the "rising" hot working fluid 244, thereby absorbing additional heat within riser annular gap 224 (e.g., from exposed surfaces 140-S and 212 of collector cylinders 210 in reactor containment system 140 and riser annular gap 224). As a result, circulation of working fluid 240 through reactor coolant system 130 may be induced and maintained without forcibly inducing such circulation (e.g., by a blower within reactor coolant system 130). It will be appreciated that in some exemplary embodiments, at least a portion of the reactor cooling system 130 (e.g., the intake system 112, the exhaust system 122, etc.) may include an air-moving device (e.g., a blower) configured to at least partially induce a flow of the working fluid 240 through the circuit 236 of the reactor cooling system 130.

[0065] As shown, the reactor coolant system 130 may comprise a non-isolated section including a non-vibration-isolated inlet section 110 configured to direct cold working fluid 242 from the ambient environment 123 to a bottom opening 224-B of the riser annular gap 224 via the downcomer annular gap 214, and a non-vibration-isolated exhaust section 120 configured to direct hot working fluid 244 from the MIRSS assembly 200 to the ambient environment 123. The non-vibration-isolated exhaust section 110 may comprise an inlet system 112 (e.g., an opening open to the ambient environment 123), one or more non-vibration-isolated inlet conduits 116 configured to direct cold working fluid 242 from the ambient environment 123 to the downcomer annular gap 214, and the process tube annular gap 214 itself. Non-vibration-isolated air intake section 110 may further include, but is not limited to, one or more air intake conduits 118 configured to couple one or more non-vibration-isolated air intake conduits 116 to downcomer annular gap 214. Non-vibration-isolated air exhaust section 120 may include one or more non-vibration-isolated air exhaust conduits 126 and an exhaust system 122 (e.g., a chimney) open to the surrounding environment 123.

[0066] As described further herein, at least a portion of reactor cooling system 130 may include a seismically isolated exhaust 232 disposed in fluid communication between non-isolated inlet 110 and non-isolated exhaust 120, which may include one or more isolation conduits defined at least in part by structures and / or surfaces of isolation assembly 190, including MIRSS assembly 200 and reactor containment system 140. Reactor cooling system 130 may include one or more conduits, passages, etc., including inlet conduit 118 (which may be an inlet annular gap, as shown in FIGS. 1A-1H ) and downcomer annular gap 214, defined between the isolation and non-isolated structures. In some exemplary embodiments, one or more of conduits 116, 118, 126, inlet system 112, and / or exhaust system 122 may be omitted from reactor cooling system 130.

[0067] 1A-1H , the nuclear power plant 100 includes a plurality of seismic isolators 150 configured to be coupled to (e.g., mounted to, structurally supported by, etc.) the reactor building 102 and thereby structurally support one or more structural loads on the reactor building 102. As shown, the reactor building 102 may include a lower building structure 102-1 having one or more structural support surfaces 102-12, and the seismic isolators 150 may be mounted on the one or more structural support surfaces 102-12 such that the seismic isolators 150 are configured to structurally support one or more structural loads on the lower building structure 102-1 via the one or more structural support surfaces 102-12. The seismic isolators 150 may be coupled to (e.g., mounted to) the lower building structure 102-1 based on metal (e.g., steel) elements of the seismic isolators 150 being at least partially embedded within the concrete structure of the lower building structure 102-1, although example embodiments are not limited in this regard. For example, the isolator 150 may be clamped, anchored, etc., via one or more structural support surfaces 102-12 to one or more reinforced concrete foundations including a reinforcing steel structure embedded within the concrete of the underlying building structure 102-1. The isolator 150 is configured to structurally support structural loads and further configured to allow movement (e.g., three-dimensional translational and / or rotational movement) of the supported structural loads relative to the structural support surfaces 102-12 to which the isolator 150 is mounted. As a result, as shown in FIGS. 1A-1H, the isolator 150 is configured to isolate structural loads supported from the reactor building 102.

[0068] Isolator 150 may include any known isolator that may be configured to allow two-dimensional or three-dimensional movement (e.g., translational and / or rotational movement) of a supported structure independent of the structure to which it is mounted. Such isolators, in some exemplary embodiments, may include one or more spring structures, one or more earthquake-related fluid damping devices, etc.

[0069] 1A-1H and 2A-2G, the nuclear power plant 100 may include a modular reactor isolation support system (MIRSS) assembly 200 configured to structurally support the reactor containment system 140 on the isolators 150 to define a seismic isolation assembly 190, and further configured to at least partially define a flowpath of the reactor coolant system 130, at least partially define a reactor head access area (HAA) 292 above the reactor containment system 140, seal the HAA 292 from the flowpath of the reactor coolant system, and, in some example embodiments, provide shielding (e.g., radiation and / or thermal shielding) for various structures, equipment, and / or spaces external to the isolation assembly 190. For simplicity, the description herein will refer to a MIRSS assembly 200, but it will be understood that any MIRSS assembly 200 or modular reactor isolation support system (MIRSS) assembly 200 described herein may be any reactor support assembly according to any of the exemplary embodiments, including either a modular reactor isolation support system (MIRSS) assembly made up of multiple structures (e.g., multiple MIRSS modules) at least partially connected together, or a non-modular reactor isolation support system (IRSS) made up of pre-fabricated modules at least partially assembled as a single structure without being connected together.

[0070] In some exemplary embodiments, the MIRSS assembly 200 may be modular, simple, and cost-effective, enabling an improved practical (e.g., reduced construction costs, time expenditures, complexity, etc.) approach to constructing the nuclear power plant 100. The MIRSS assembly 200 may include a support structure, also referred to herein as annular structure 230, configured to be seismically isolated from the reactor building 102 in which the nuclear reactor 142 is housed (e.g., contained and structurally supported), and configured to seismically isolate the reactor containment system 140 from the reactor building 102 by structurally supporting the reactor containment system 140 (e.g., structurally supporting the overall structural loads of the reactor containment system 140) on seismic isolators coupled to the reactor building 102. Such annular structure 230 may be a steel structure including and defined by steel structural members (e.g., beams, plates, girders, etc.) that may be connected together via known techniques (e.g., welding, riveting, etc.), although exemplary embodiments are not limited thereto. In some exemplary embodiments, the annular structure 230 may comprise different materials (eg, carbon steel, stainless steel, etc.).

[0071] Because the MIRSS assembly 200 may be seismically isolated from the reactor building structure, the MIRSS assembly 200 may be configured to be assembled (e.g., constructed) independently of the reactor building 102 and then installed (e.g., mounted) as a single-piece structure at the reactor building construction site (e.g., on the seismic isolator 150 already mounted on the building structures 102-1 and / or 102-2). Such assembly and installation of the MIRSS assembly 200 may reduce the structural weight of the seismically isolated reactor support structure and the cost and / or complexity of its construction by significantly reducing, minimizing, or eliminating the support structure construction process, including embedding the reinforcing steel of the cylindrical reactor support structure in the concrete of the reactor building structures 102-1, 102-2, etc. The MIRSS assembly 200 may be constructed in parallel with and independently of the reactor containment system 140. For example, reactor enablement system 140, collector cylinder 210, and bulkhead 222 may be constructed (e.g., fabricated) in parallel. Once assembled, MIRSS assembly 200 and reactor containment system 140 may be lifted as a unit (e.g., as a single-piece structure) and placed within containment pit 102-11 such that MIRSS assembly 200 rests on and is structurally supported (e.g., solely structurally supported) by seismic isolators 150. In some exemplary embodiments, MIRSS assembly 200 may be lifted as a unit and loaded onto seismic isolators 150 independently of reactor containment system 140, and then lifted and loaded onto the already loaded MIRSS assembly 200. In some exemplary embodiments, a portion of the reactor containment system 140 (e.g., the protective vessel 144) may be mounted on the MIRSS 200 before the MIRSS assembly 200 is mounted on the seismic isolation device 150, and the remaining portions of the reactor containment system 140 (e.g., the primary vessel 146, the reactor 142, etc.) may be coupled to the mounting portion of the reactor containment system 140 after the MIRSS assembly 200 is mounted on the seismic isolation device 150, thereby completing construction of the reactor containment system 140.MIRSS assembly 200 may be configured to allow for lightweight lift-out due to the absence of shielding 390 within at least cylindrical reactor support structure 202 at this step in the assembly process. Once MIRSS assembly 200 is in the desired location (e.g., mounted on isolators 150), shielding 390 can be provided within cylindrical reactor support structure 202 (e.g., within one or more shielded chambers 392 thereof). At this point, at least a portion of reactor containment system 140 and its internal elements (e.g., protective vessel 144, primary vessel 146, reactor 142, head 148, etc.) can be lifted into position or assembled within reactor building 102. In some exemplary embodiments, at least a portion of the shielding material 390 may be added, provided, or built into the MIRSS assembly 200 prior to the MIRSS assembly 200 being loaded onto the isolator 150 (e.g., prior to the MIRSS assembly 200 being lifted as a unit and loaded onto the isolator 150). For example, in some exemplary embodiments, the first lower shielding material 328-1 (e.g., a heat shield) may be installed as part of the MIRSS assembly 200 during construction of the MIRSS assembly 200 prior to the MIRSS assembly 200 being lifted as a single unit and loaded onto the isolator 150. As another example, in some exemplary embodiments, upper shielding material 318 may be delivered to interior 204 of cylindrical reactor support structure 202 to partially or fully fill a portion of interior 204 not occupied by exhaust duct 216 during construction of MIRSS assembly 200 prior to MIRSS assembly 200 being raised as a single unit and installed on isolator 150. In some exemplary embodiments, at least a portion of shielding material 390 may be pumped into one or more shielded chambers 392 via a boom pump, although exemplary embodiments are not limited in this regard. For example, in exemplary embodiments in which shielding material 318 may be steel balls that may be delivered to interior 204 of cylindrical reactor support structure 202, upper shielding material 318 may be placed in interior 204, pumped into interior 204 as bulk material, or delivered to interior 204 via a mechanism other than a pump.

[0072] As shown in at least Figures 1A-1H and 2A-2G, MIRSS assembly 200 may include structural members 302, which may be steel structural members (e.g., plate steel, steel girders, steel beams, etc.), where steel may be understood herein to include stainless steel, and which may collectively comprise and / or define at least a cylindrical reactor support structure 202, a bulkhead 222 having an outer cylindrical surface 223, a collector cylinder 210 having an inner cylindrical surface 212, an HAA seal 294, and / or one or more shielded chambers 392 configured to hold one or more shielding materials 390 therein.

[0073] As further shown, MIRSS assembly 200 may include an exhaust duct 216 extending from collector cylinder 210 through the interior of cylindrical reactor support structure 202, e.g., to establish fluid communication from collector cylinder 210 to a radially exterior portion of MIRSS assembly 200 via interior 218 of MIRSS assembly 200. In some exemplary embodiments, MIRSS assembly 200 may include an exhaust manifold structure 610 that may be coupled to annular structure 230 (e.g., cylindrical reactor support structure 202) and may include one or more exhaust duct structures 612 configured to at least partially define one or more exhaust ducts 216 (e.g., define at least one or more duct sidewalls of one or more exhaust ducts 216) based on the exhaust manifold structure 610 being coupled to annular structure 230. However, example embodiments are not limited in this regard, and in some example embodiments, MIRSS assembly 200 may not include any separate exhaust manifold structure 610 coupled to annular structure 230, and exhaust duct 216 may be defined by structural members 302 of cylindrical reactor support structure 202. In some example embodiments, seismic isolator 150 may also be considered part of MIRSS assembly 200, although example embodiments are not limited in this regard. In some example embodiments, seismic isolator 150 is considered separate from MIRSS assembly 200. Once assembled, MIRSS assembly components, including MIRSS assembly 200, are configured to collectively operate as a unit under normal and earthquake-related conditions.

[0074] Once the MIRSS assembly 200 is fully assembled (e.g., constructed) and mounted on the seismic isolation device 150, the MIRSS assembly 200 may be configured to act as a unit (e.g., as a single-piece structure) such that movement of the seismic isolation assembly 190 (including the collector cylinder 210, reactor containment system 140, bulkhead 222, cylindrical reactor support structure 202, and floor structure 290) can be controlled independently of the reactor building 102 and HAA 292 during an earthquake-related event. The MIRSS assembly 200 is configured to allow for close tolerances (e.g., small radial thickness, annular diameter, etc. of the riser annular gap 224) between the reactor containment system 140 and the collector cylinder 210 (e.g., between the outer sidewall surface 140-S of the reactor containment system 140 and the inner cylindrical surface 212 of the collector cylinder 210) due to both being contained within the isolation assembly 190. As a result, the radial thickness of the riser annular gap 224 can be fixed or substantially fixed during earthquake-induced movement of the isolation assembly 190 relative to the reactor building 102. Such close tolerances may, in turn, improve heat removal by the reactor coolant system 130 by increasing the viscosity (e.g., vertical flow viscosity) of the hot working fluid 244 in the riser annular gap 224 and may allow the radial thickness of the downcomer annular gap 214 to be increased without increasing the diameter of the containment pit 102-11. As a result, form losses from the cold working fluid 242 flowing down into the containment pit 102-11 may be reduced because there is more space to make a 90-degree turn from the bottom opening 214-B of the downcomer annular gap 214 to the bottom opening 224-B of the riser annular gap 224. Additionally, such improved heat removal by the reactor coolant system 130 may enable the reactor 142 to operate at higher operating temperatures, thus improving operational performance and / or efficiency.Furthermore, because the MIRSS assembly 200 includes metallic structural members 302, including, for example, steel structural members 302, the nuclear power plant 100 may be configured to operate the reactor 142 at a higher average operating temperature than a nuclear power plant in which the riser annular gap 224 and / or exhaust duct 216 are at least partially defined by a reactor support structure that at least partially structurally supports the reactor containment system 140 on the isolator 150 and includes concrete and / or reinforced concrete.

[0075] The MIRSS assembly 200 is configured to significantly reduce the construction costs of the nuclear power plant 100. For example, because the nuclear power plant 100 utilizes portions of the building structures 102-1 and / or 102-2 below and / or above the reactor building 102 to provide seismic isolation (referred to herein as building isolation), the primary operating cost in current nuclear power plant 100 designs is due to construction, including, but not limited to, excavation, concrete, rebar, and labor. Building isolation configurations can be expensive to construct and analyze. A seismic isolator 150 placed below (e.g., structurally supporting) the entire reactor building 102 or below the floating containment pit 102-11 would be very expensive to construct and difficult to access for maintenance or replacement. The MIRSS assembly 200 positions the seismic isolator 150 above the coolant location within the reactor containment system 140, reducing the risk of damage to the seismic isolator 150 in the event of a loss of coolant accident (LOCA), by reducing the cost of enabling the seismic isolator 150 to be mounted on one or more structural support surfaces 102-12 above the containment pit 102-11.

[0076] The MIRSSS assembly 200 is configured to significantly reduce earthquake-induced stresses on all components of the reactor containment system 140 (e.g., the reactor 142, the protective vessel 144, the primary vessel 146, and the head 148), thereby reducing the engineering, material, and fabrication costs of the nuclear power plant 100's most expensive components and equipment, which account for a large share of the cost of a nuclear power plant. The MIRSS assembly 200 may further be configured to reduce relative movement between the reactor containment system 140 and the collector cylinder 210 (e.g., between at least the protective vessel 144 and the collector cylinder 210) during an earthquake-related event due to the inclusion of both the collector cylinder 210 and the reactor containment system 140 in the seismic isolation assembly 190. As a result, the MIRSS assembly 200 is configured to reduce, minimize, or prevent damage due to contact and collision between the reactor containment system 140 and the collector cylinder 210 (e.g., reduce, minimize, or prevent damage due to contact and collision between the protective vessel 144 and the collector cylinder 210), and may further be configured to reduce, minimize, or prevent closure of the riser annular gap 224, which in turn may reduce, minimize, or prevent the operation of the reactor coolant system 130 from being impaired by such closure. Additionally, the MIRSS assembly 200 may be configured to reduce relative movement between the protective vessel 144 and the primary vessel 146 of the reactor containment system 140 during an earthquake-related event due to the reactor containment system 140 being included in the seismic isolation assembly 190. As a result, the MIRSS assembly 200 is configured to reduce, minimize, or prevent damage due to contact and collision between the protective vessel 144 and the primary vessel 146 of the reactor containment system 140, and may also be configured to reduce, minimize, or prevent annular gaps between the protective vessel 144 and the primary vessel 146, which may in turn reduce, minimize, or prevent the possibility that operation of the reactor coolant system 130 may be impaired by such closure.

[0077] 1A-1H and 2A-2G, collector cylinder 210 of MIRSS assembly 200 defines a cylindrical space that may accommodate at least a portion of reactor containment system 140 (e.g., at least a portion of protective vessel 144). As further shown, MIRSS assembly 200 includes a cylindrical reactor support structure 202 configured to structurally support reactor containment system 140 from a top portion 140-P thereof (which may be a portion of a radial edge of head 148 and / or protective vessel 144) proximate to an upper surface 140-U of reactor containment system 140 (which may be a portion of an upper surface 148-U of head 148). As a result, the cylindrical reactor support structure 202 is configured to surround the reactor containment system 140 mounted thereon, such that the supported reactor containment system 140 (e.g., at least the protective vessel 144) may at least partially "hang" from the cylindrical reactor support structure 202 and extend at least partially downward from the cylindrical reactor support structure 202 into the cylindrical space defined by the collector cylinder 210. In some exemplary embodiments, a well seal 293, which may be an annular seal, may be positioned between the cylindrical reactor support structure 202 and the reactor containment system 140 (e.g., between the cylindrical reactor support structure 202 and the protective vessel 144) to seal the interface between the reactor containment system 140 and the cylindrical reactor support structure 202 and to seal the top 224-U of the riser annular gap 224 defined between the collector cylinder 210 and the reactor containment system 140 (e.g., between the collector cylinder 210 and the protective vessel 144). Thus, well seal 298 may seal top 224-U of riser annular gap 224, and thus at least a portion of circuit 236 of reactor coolant system 130, from reactor head access area (HAA) 292 located above reactor containment system 140 and MIRSS assembly 200. In some exemplary embodiments, well seal 298 may be considered to be part of MIRSS assembly 200, including, for example, a portion of cylindrical reactor support structure 202.The well seal 298 may comprise (partially or entirely) a flexible material, such as Inconel 625, Inconel 718, stainless steel 316, stainless steel 304, a fluoroelastomer material (which may be referred to as a fluoroelastomer sealing material), a fluorocarbon elastomer (FKM) polymer material, or the like.

[0078] 1A-1H and further shown in FIG. 2G, the MIRSS assembly 200 is configured to be structurally supported to the cylindrical reactor support structure 202 (e.g., via one or more structural members 302 comprising the cylindrical reactor support structure 202) on a seismic isolator 150 coupled to the reactor building 102 on the structural support surface 102-12 of the lower building structure 102-1. As a result, the cylindrical reactor support structure 202 is configured to transfer the overall structural load (e.g., total weight) of the MIRSS assembly 200 and reactor containment system 140 supported therein to the reactor building 102 (e.g., lower building structure 102-1) via the seismic isolator 150. In some exemplary embodiments, the overall structural load (e.g., total weight) of the MIRSS assembly 200 may be structurally supported by the seismic isolator 150, as shown in FIGS. 1A-1H. As a result, the MIRSS assembly 200 and the reactor containment system 140 may be vibrationally isolated from the reactor building 102 by the isolators 150 and thus may be configured to move together independently of each other and the reactor building 102. Thus, the MIRSS assembly 200 and the reactor containment system 140 may collectively define a vibration isolation assembly 190 that is vibrationally isolated from the reactor building 102.

[0079] 1A-1H and 2A-2G, bulkhead 222 of MIRSS assembly 200 has an outer cylindrical surface 223 that may face an opening surface of reactor building 102 (e.g., inner containment pit surface 102-11S of containment pit 102-11). Thus, outer cylindrical surface 223 of bulkhead 222, together with the opposing surface of reactor building 102, may define a vertically extending downcomer annular gap 214 between bulkhead 222 of MIRSS assembly 200 and reactor building 102. As further shown, collector cylinder 210 has an inner cylindrical surface 212 that may face an opposing outer sidewall surface 140-S of reactor containment system 140. Thus, the inner cylindrical surface 212, together with the opposing outer sidewall surface 140-S, may at least partially define (e.g., define at least each of the outer and inner circular diameters of) a riser annular gap 224 extending vertically between the collector cylinder 210 of the MIRSS assembly 200 and the reactor containment system 140. It will be appreciated that the outer sidewall surface 140-S of the reactor containment system 140 may be the outer sidewall surface 144-S of a protective vessel 144 of the reactor containment system 140, although example embodiments are not limited thereto. For example, in some example embodiments in which the reactor containment system 140 does not include any protective vessel, the outer sidewall surface 140-S of the reactor containment system 140 may be the outer sidewall surface of a primary vessel 146 of the reactor containment system 140.

[0080] As further shown, MIRSS assembly 200 may be further configured to define an air sink 234 disposed below bottom openings 224-B and 214-B of riser annular gap 224 and downcomer annular gap 214, respectively (e.g., within containment pit 102-11 below MIRSS assembly 200). Air sink 234 may be open toward both bottom openings 224-B and 214-B. As a result, downcomer annular gap 214 and riser annular gap 224 may be radially isolated from one another from a central longitudinal axis of MIRSS assembly 200, reactor containment system 140, etc., yet may be in open fluid communication with one another via bottom openings 214-B and 224-B and air sink 234.

[0081] As shown in at least Figures 1A-1H, the reactor cooling system 130 may be at least partially defined by, either directly or by at least partially and circumferentially (e.g., azimuthally) surrounding a lower portion (e.g., inlet annular gap) of the cylindrical reactor support structure 202, and may include a non-vibration-isolated inlet duct 116 having respective openings 116-O opening into the downcomer annular gap 214 via intervening ducts such as one or more inlet ducts 118, which may be axial between the cylindrical reactor support structure 202 and the structural support surface 102-12. As a result, the MIRSS assembly 200 may be configured to direct the cold working fluid 242 to be drawn into the reactor cooling system 130 (e.g., via the air intake system 112 and one or more conduits 116), into the top opening 214-U of the downcomer annular gap 214, and to flow vertically downward toward the bottom opening 214-B of the downcomer annular gap 214 defined between the gap 222 and the reactor building structure 102.

[0082] As further illustrated, the heated high-temperature working fluid 244 "rising" vertically through the riser annular gap 224 may rise (e.g., by being displaced at the bottom opening 224-B of the riser annular gap 224 by the incoming additional cold working fluid 242) to the top 224-U of the riser annular gap 224 adjacent the top boundary of the riser annular gap 224. As further illustrated, the MIRSS assembly 200 may include one or more structural members 302 (e.g., steel structural members) that may singly or collectively define one or more inlet openings 216-O1 in the top portion 210- of the collector cylinder 210 that open to (e.g., open directly to) the top 224-U of the riser annular gap 224. One or more structural members 302 of the MIRSS assembly 200 may singly or collectively define one or more outlet openings 216-O2 in an outer sidewall surface 200-S of the MIRSS assembly 200 (which may be an outer circumferential sidewall of the cylindrical reactor support structure 202). The one or more structural members 302 of the MIRSS assembly 200 may at least partially define one or more exhaust ducts 216 each extending from the collector cylinder 210 through an interior 218 of the MIRSS assembly 200, for example, between one or more inlet openings 216-O1 and one or more outlet openings 216-O2. The MIRSS assembly 200 may be configured to direct the heated high-temperature working fluid 244 to rise through the riser annular gap 224 to its top 224-U and further flow from the top 224-U of the riser annular gap 224 at the top 210-U of the collector cylinder 210 through the interior 218 of the MIRSS assembly 200 (e.g., through the interior 204 of the cylindrical reactor support structure 202) to the outside of the MIRSS assembly 200 via one or more exhaust ducts 216. As shown, one or more exhaust ducts 216 may be azimuthally spaced around the collector cylinder 210 to allow a relatively uniform vertical flow of the high-temperature working fluid 244 upward and out the top 224-U of the riser annular gap 224, thereby mitigating heat buildup within the riser annular gap 224 and improving axial / azimuthal cooling uniformity of the reactor containment system 140 (e.g., improving cooling uniformity of at least the protective vessel 144).It will be understood that the interior 218 of the MIRSS assembly 200 may comprise one or more containments, cavities, etc. defined by the interior surfaces of one or more structural members 302 (e.g., beams, plates, girders, etc., which may be steel beams, steel plates, steel girders, etc.) of the MIRSS assembly 200. It will be understood that "azimuthal" or "azimuthally" may be interchanged herein with "circumferential" or "circumferentially," respectively.

[0083] 1A-1H and 2A-2G, the portions of reactor cooling system 130 contained within and / or defined within isolation assembly 190 may be considered to be the seismically isolated portion of reactor cooling system 130, and other portions of reactor cooling system 130 disposed outside isolation assembly 190 may be considered to be the non-seismically isolated portion of reactor cooling system 130. As shown, MIRSS assembly 200 may be configured to define and / or establish at least a seismically isolated exhaust portion 232 of reactor cooling system 130, which is configured to be coupled in fluid communication with non-seismically isolated exhaust portion 120 of reactor cooling system 130. As shown, isolated exhaust portion 232 of reactor cooling system 130 may include riser annular gap 224 and exhaust duct 216.

[0084] With further reference to Figures 1A-1H and 2A-2G, and additionally with reference to Figures 6A-6C, MIRSS assembly 200 may include exhaust manifold structures 610 that may be coupled to annular structure 230 of MIRSS assembly 200 and may each be configured to define one or more exhaust ducts 216 and may further be configured to direct high-temperature working fluid 244 to exit top 224-U of riser annular gap 224 through openings 610-O1, which may extend to and / or through openings 216-O1, and to exit MIRSS assembly 200 through outlet openings 610-O2. The outlet opening 610-O2 of the exhaust manifold structure 610 may be coupled to the opening 126-O1 of the non-isolated exhaust conduit 126 of the non-isolated exhaust section 120 of the reactor coolant system 130, for example, via a flexible duct 620 coupled between the opening 610-O2 and 126-O1 to establish fluid communication between the collector cylinder 210 and the non-isolated exhaust section 120 via one or more conduits of the MIRSS assembly 200. As shown, the non-isolated exhaust conduit 126 may extend through the upper building structure 102-2 through one or more openings 102-2O, although example embodiments are not limited in this regard. In some exemplary embodiments, a flexible duct 620 connected to at least one exhaust duct 216 of the MIRSS assembly 200 (e.g., based on being connected to the second opening 610-O2 of the exhaust manifold structure 610) may extend at least partially through one or more openings 102-O2 in the upper building structure 102-2 and connect with an opening 126-O1 of the non-vibration-isolated exhaust conduit 126.

[0085] As shown, reactor coolant system 130 may define a circulation path 236 including at least air inlet system 112, one or more non-vibration-isolated air inlet ducts 116, air inlet duct 118, downcomer annular gap 214, air sink 234, riser annular gap 224, exhaust duct 126, flexible duct 620, one or more non-vibration-isolated exhaust ducts 126, and exhaust system 122. It will be understood that in some exemplary embodiments, one or more of non-vibration-isolated air inlet duct 116 and / or non-vibration-isolated exhaust duct 126 may be omitted. For example, in some exemplary embodiments, non-vibration-isolated exhaust duct 126 may be directly coupled between exhaust system 122, such as a stack or duct configured to discharge high-temperature working fluid 244 from non-vibration-isolated exhaust duct 126 directly to the surrounding environment 123, and flexible duct 620.

[0086] Because portions of the reactor cooling system 130, particularly the non-isolated exhaust section 120, are located external to the isolation assembly 190 and are therefore not structurally supported by the isolator 150 or the MIRSS assembly 200, the MIRSS assembly 200 may be lighter due to the reduced structural load that the cylindrical reactor support structure 202 supports on the isolator, while the MIRSS assembly 200 may be configured to maintain the integrity of the reactor cooling system 130 even during movement of at least the isolated exhaust section 232 relative to the non-isolated exhaust section 120. Additionally, because the isolator 150 does not structurally support at least the non-isolated exhaust section 120 of the reactor cooling system 130, the structural load requirements of the isolator 150 may also be reduced, which may reduce component and construction costs of the nuclear power plant. This may potentially further reduce the structural support requirements of the underlying lower building structure 102-1 and / or the foundation 170 of the reactor building 102, since the non-isolated exhaust section 120 (e.g., the stack of the exhaust system 122) is at least partially located outside the reactor building 102 and connected thereto via the non-isolated conduits 116 and / or 126. Additionally, as shown, the configuration in which the isolation assembly 190 moves independently of the reactor building 102 allows the downcomer annular gap 214 defined between the MIRSS assembly 200 and the reactor building 102 to deform and accommodate relative movement of the MIRSS assembly 200 with respect to the reactor building 102, while maintaining fluid communication between the inlet opening 116-O and the riser annular gap 224 at least via the downcomer annular gap 214. As a result, MIRSS assembly 200 may configure reactor cooling system 130 to be more reliable by resisting closure of circuit 236 due to earthquake-related events, while also reducing the overall structural load on MIRSS assembly 200 and isolator 150 by allowing reactor cooling system 130 to be non-isolated and external to isolation assembly 190. Accordingly, MIRSS assembly 200 and isolator 150 may have reduced structural load-bearing requirements and thus may be lighter, which may allow for a lighter reactor building 102 and reduce the cost and complexity of constructing the reactor building.

[0087] The MIRSS assembly 200 may be configured to increase the operational reliability of the reactor cooling system 130 based on significantly reducing baseline configuration losses. The MIRSS assembly 200 may be configured to increase the event response reliability of the reactor cooling system 130 based on reducing, minimizing, or preventing relative movement between flow conduit surfaces of the reactor cooling system 130 (e.g., between the opposing inner cylindrical surface 212 and outer sidewall surface 140-S, which are coupled together and contained within the isolation assembly 190 to define the riser annular gap 224), thereby reducing the likelihood of localized configuration losses that could disrupt the operation of the reactor cooling system 130.

[0088] In some exemplary embodiments, MIRSS assembly 200 may be configured to prevent shielding, including radiation shielding (also referred to as radiological shielding) and / or thermal shielding, of various components of reactor building 102 and / or equipment therein, including, for example, seismic isolators 150, from reactor containment system 140 and reactor 142 contained therein. For example, with further reference to FIGS. 1A-1H and 2A-2G , MIRSS assembly 200 may include structural member 302 that defines one or more shielded chambers 392 in interior 218 of MIRSS assembly 200 (e.g., interior 204 of cylindrical reactor support structure 202, such as radially between collector cylinder 210 and bulkhead 222). One or more shielded chambers 392 may at least partially circumferentially surround reactor containment system 140 (e.g., at least protective vessel 144) and / or collector cylinder 210 and may be configured to hold at least one shielding material 390 therein. For example, MIRSS assembly 200 may include structural members 302 (e.g., beams, plates, girders, etc., which may be steel beams, plates, girders, etc.) collectively defining one or more upper and / or lower shielded chambers 316 and / or 326 within MIRSS assembly 200, which may house (or be filled with) one or more shielding materials 390. Such one or more shielding materials 390 may include radiation and / or thermal shielding materials (e.g., insulation). Such shielding materials may thus shield elements located outside MIRSS assembly 200 within reactor building 102, including, for example, isolators 150, reactor HAA 292, downcomer annular gap 214, air inlet conduit 118, any combination thereof, etc.

[0089] The MIRSS assembly 200 may be configured to facilitate construction of the nuclear power plant 100 based on simplified installation of shielding 390 to shield (e.g., radiation and / or thermal) various structures and / or areas within the reactor building 102 from the reactor 142 and / or reactor containment system 140. For example, the MIRSS assembly 200 initially installed within the reactor building 102 on the seismic isolator 150 may omit any shielding 390 in one or more of the shielded chambers 392 such that the initial absence of shielding 390 therein results in a relatively light weight of the MIRSS assembly 200 during installation (e.g., onboard) on the seismic isolator 150. The MIRSS assembly 200 may be lifted (e.g., raised) and lowered onto the isolators 150 as a single-piece structure, which may simplify and facilitate installation of the support structure provided by the MIRSS assembly 200 within the reactor building 102, which may, for example, significantly reduce the requirement for embedding reinforcing steel in the concrete of the reactor building 102. Additionally, the MIRSS assembly 200 may be configured to allow one or more shielding materials 390 to be loaded into one or more of the upper shielding chambers 392 defined by the structure of the cylindrical reactor support structure 202 after the MIRSS assembly 200 is mounted on the isolators 150, for example, by pumping the shielding materials 390 into the upper shielding chambers 316 defined by the structure of the cylindrical reactor support structure 202.

[0090] For example, by providing shielding material 390 in one or more of the shielded chambers 392 of the MIRSS assembly 200 after the MIRSS assembly 200 is mounted on the vibration isolation device 150, the MIRSS assembly 200 is at least partially installed (e.g., mounted) within the reactor building before the shielding material is installed (e.g., provided) within one or more of the shielded chambers of the MIRSS assembly 200, thereby enabling lightweight lifting by a crane into the reactor building since the absence of shielding material on the structure during crane installation (e.g., crane lifting) results in a significantly lighter structure being installed by the crane, simplifying installation of the structure in the reactor building. Additionally, in an exemplary embodiment, shielding material 390 may be supplied (e.g., pumped) into lower shielding chamber 326 of the MIRSS assembly, which may at least partially define partition 222 between concentric downcomer annular gap 214 and riser annular gap 224, to shield radiation (e.g., gamma ray radiation and / or neutron radiation) and / or heat radiation into inlet conduit 118 and / or downcomer annular gap 214.

[0091] It will be appreciated that in some exemplary embodiments, MIRSS assembly 200 may be configured to house different shielding materials 390 or combinations of shielding materials 390 in various shielded chambers 392 based on one or more types of radiation to be shielded by MIRSS assembly 200, which may be based on the reactor type of reactor 142 in reactor containment system 140 structurally supported by MIRSS assembly 200. For example, if reactor 142 is a liquid sodium reactor, at least a portion of the shielding material 390 in MIRSS assembly 200 (e.g., upper shielding 318) may be a radiation shielding material configured to shield against gamma ray radiation (e.g., gamma rays). In other embodiments, if reactor 142 is a molten salt reactor, at least a portion of the shielding material 390 in MIRSS assembly 200 (e.g., upper shielding 318) may be a radiation shielding material configured to shield against gamma ray radiation (e.g., gamma rays) in addition to neutron radiation (e.g., neutrons).

[0092] As described herein, the shielding material 390 (e.g., any of the upper shielding material 318, the first lower shielding material 328-1, or the second lower shielding material 328-2) may include a radiation shielding material configured to provide radiation shielding (e.g., absorbing and / or reflecting radiation emanating from a radiation source to reduce material penetration of the radiation), thermal insulation (e.g., thermal insulation, e.g., fiberglass, calcium silicate, etc.), or any combination thereof. The shielding material 390 may be configured to be injected into the shielding chamber 392 to occupy (e.g., fill) the shielding chamber 392. For example, the shielding material 390 may include a high-density concrete radiation shielding material, including one or more of DENSECRETE®, SHIELDBLOCK®, and / or SHIELDGROUT®. In other embodiments, shielding material 390 may include one or more high-density (heavy-duty) aggregates, including high-density materials used to make high-density concrete, including materials such as barite, ferrophosphate, limonite, hematite, ilmenite, magnetite, goethite, steel punchings, and / or steel shot. In other embodiments, shielding material 390 may include basalt concrete, steel balls, stainless steel, depleted uranium, depleted uranium-composite materials, lead, lead-composite materials, lead metal shot (e.g., 2 mm diameter lead balls), and / or tungsten shot (tungsten balls). In other examples, shielding material 390 may include a chemically bonded oxide-phosphate ceramic with unique radiation shielding properties. In other examples, the shielding material 390 may include a metal foam material that may include hollow metal spheres of one metal dispersed in a matrix that may include the same or a different metal (e.g., stainless steel spheres dispersed in a matrix of high speed T15 steel, an alloy containing trace amounts of vanadium and tungsten), which may be poured to occupy the shielding chamber 392.

[0093] In some exemplary embodiments, the heat shields described herein may include any material, structure, board, panel, etc. configured to provide heat insulation, thermal insulation, etc. The heat shields may include foam materials, ceramic materials, thermal insulating materials, or any combination thereof. The heat shields may include, but are not limited to, glass wool, rock wool, calcium silicate, cellular glass, expanded polystyrene (PS), extruded polystyrene (XPS), polyurethane (PUR), phenolic foam, polyisocyanurate foam (PIR), aerogel (e.g., silica aerogel), one or more vacuum panels (also referred to herein as vacuum insulation panels), one or more BTU-BLOCK® boards 1807 / 18 boards, one or more WDS® Ultra Plus boards, any combination thereof, one or more SOLIMIDE® thermal insulating foam structures, etc.

[0094] 1A-1H and 2A-2G, the MIRSS assembly 200 may include a structural member 302 (e.g., a steel structural member) configured to radially and concentrically space the collector cylinder 210 and the partition wall 222 to establish a thermal expansion break therebetween to mitigate radiant heat transfer from the collector cylinder 210 to the partition wall 222 across the annular space. Such an annular space may include a shielded chamber 326 and may include one or more heat shields to radially insulate the collector cylinder 210 from the partition wall 222. For example, the MIRSS assembly 200 may be configured to house a first lower shield 328-1, which is an insulator (e.g., a heat shield) in a first lower shielded chamber 326-1 radially between the collector cylinder 210 and the partition wall 222 and is configured to radially insulate the partition wall 222 from the collector cylinder 210 to at least partially establish the thermal expansion break. The first lower shield 328-1 may include an optional thermal insulation material. Such a thermal expansion break may reduce, minimize, or prevent heat transfer (e.g., via wicking) from the hot working fluid 244 in the riser annular gap 224 to the cold working fluid 242 in the downcomer annular gap 214 through the MIRSS assembly 200, thereby improving heat transfer performance and “natural” air circulation within the reactor coolant system 130, which is driven at least in part by density differences between the cold working fluid 242 and the hot working fluid 244 due to temperature differences between the two.

[0095] 1A-1H and 2A-2G , in some exemplary embodiments, MIRSS assembly 200 is configured to facilitate inherent cooling of isolators 150 on which MIRSS assembly 200 is mounted. For example, in some exemplary embodiments, MIRSS assembly 200 may include one or more isolators 150 to at least partially define inlet conduit 118 in fluid communication with reactor coolant system circuit 236, e.g., between inlet opening 116-O of non-isolated inlet conduit 116 and top opening 214-U of downcomer annular gap 214. Accordingly, MIRSS assembly 200 may be configured to direct cold working fluid 242 to flow through a heat transfer path that passes through isolators 150, such that isolators 150 are in heat transfer communication with, and may be cooled by, cold working fluid 242. In some exemplary embodiments, the isolators 150 may be disposed in the downcomer annular gap 214, one or more of the inlet conduits 118, or one or more of the non-isolated inlet conduits 116. Such cooling of the isolators 150 may maintain the isolators 150 within a desired design temperature range due to the passive nature of the inlet air flow path through the inlet conduits 118 or within the downcomer annular gap 214. The isolators 150 within the inlet air flow path (e.g., within the inlet conduits 118 or downcomer annular gap 214) may be configured to make the nuclear power plant 100 more resilient to unforeseen events, such as various events or accidents, that may result in increased thermal loads on the isolators 150. In the event of an accident or event, the isolators 150 may be protected by such independent cooling. Therefore, the independent cooling of the vibration isolation device 150, which structurally supports and isolates the MIRSS assembly 200, may improve the performance and / or reliability of the nuclear power plant 100 equipped with the MIRSS assembly 200 by reducing the likelihood of damage or failure of the vibration isolation device 150 due to thermal loads.

[0096] 1A-1H, the nuclear power plant 100 may further include one or more heaters 154 configured to heat one or more of the isolators 150 disposed within the inlet conduit 118, and thus the cold working fluid 242 passing therethrough. Such heaters 154 may be configured to "locally heat" one or more of the isolators 150 to mitigate or minimize potential overcooling of the isolators 150 by the cold working fluid 242, for example, in exemplary embodiments in which the nuclear power plant 100 is exposed to relatively cold environmental conditions such that the cold working fluid 242 is relatively cold (e.g., below 0° F.) for extended periods of time. Such heaters 154H may include, for example, electrical resistance heaters, space heaters, etc. In some exemplary embodiments, the one or more heaters 154 may be coupled to the one or more isolators 150 and configured to directly heat the one or more isolators 150 through electrical conduction; for example, the one or more heaters 154 may include one or more electrical resistance heaters. In some exemplary embodiments, the one or more heaters 154 may be spaced apart (e.g., insulated from direct contact) from the isolators 150 and configured to heat the cold working fluid 242 prior to the cold working fluid 242 passing through a heat transfer path through the one or more isolators 150. Such heaters 154 may therefore be “upstream” of the one or more isolators 150 in the intake flow path of the flow of the cold working fluid 242 and configured to “preheat” the cold working fluid 242 prior to the cold working fluid 242 passing through a heat transfer path through the one or more isolators 150. In some exemplary embodiments, the nuclear power plant 100 and / or its MIRSS assembly 200 may be configured to direct at least a portion of the hot working fluid 244 to flow in a heat transfer path through one or more isolators 150, and / or may be configured to provide localized heating of the isolators at the inlet conduit 118 by direct heating of the isolators 150 and / or by "pre-heating" the cold working fluid 242 prior to it passing over one or more isolators 150.For example, the MIRSS assembly 200 may include one or more conduits, ducts, or the like extending into the inlet conduit 118 and / or in contact with one or more vibration isolators 150 such that the hot working fluid 244 flows through the one or more conduits to locally heat the cold working fluid 242 flowing through the inlet conduit 118 in a heat transfer path through the one or more conduits. Such one or more conduits may include at least a portion of the exhaust manifold structure 610, although example embodiments are not limited in this regard.

[0097] 1A-1H , the isolation assembly 190 may define a floor structure 290 of the reactor head access area (HAA) 292 housed above the floor structure 290 by an upper building structure 102-2 of the reactor building 102, which may include a cylindrical wall structure 102-21 and a roof structure 102-22, including the upper surfaces 200-U and 140-U of the MIRSS assembly 200 and reactor containment system 140, respectively, thereby isolating the floor structure 290 from the upper building structure 102-2, which houses the HAA 292 above the floor structure 290 and is configured to move independently of the upper building structure 102-2 that houses the HAA 292 above the floor structure 290 and provides upper (e.g., wall and ceiling) containment for the HAA 292. It will be understood that the upper surface 140-U of the reactor containment system 140 may be the upper surface 148-U of the head 148 of the reactor containment system 140. As further shown, the MIRSS assembly 200 may include a RAHS (RVACS Inlet Annular Gap to HAA Seal), also referred to herein as an HAA seal 294, which may be an annular seal coupled to an outer sidewall surface 200-S of the MIRSS assembly 200 and extending radially outward from the MIRSS assembly 200 to contact an inner sidewall 102-2S of the upper building structure 102-2, thereby closing and sealing the annular gap between the MIRSS assembly 200 and the upper building structure 102-2, completing the containment of the HAA 292. The HAA seal 294 may be configured to space (e.g., axially separate) the inlet conduit 118 from the HAA 292.

[0098] The HAA seal 294 may be a flexible seal configured to maintain a seal between the HAA 292 and the air inlet conduit 118 (and thus between the HAA 292 and the reactor coolant system 130) during movement of the isolated MIRSS assembly 200 relative to and independent of the non-isolated reactor building structures 102-1, 102-2 that at least partially define containment of the HAA 292. For example, the HAA seal 294 may comprise (partially or entirely) a flexible material, such as, for example, Inconel 625, Inconel 718, stainless steel 316, stainless steel 304, a fluoroelastomer material (which may also be referred to as a fluoroelastomer seal), a fluorocarbon elastomer (FKM) polymer material, or the like. Because flexible HAA seals 294 are less likely to fail during an earthquake-related event than rigid seals and are configured to reduce, minimize, or prevent the likelihood of such failure resulting in leakage at HAA 292 to reactor coolant system 130, MIRSS assembly 200 including HAA seals 294 is configured to seal HAA 292 and accommodate (e.g., accommodate) earthquake-related movement of reactor building 102 and / or isolation assembly 190, thereby improving the reliability of operation of reactor coolant system 130. As a result, HAA seals 294 may be configured to improve the reliability of reactor coolant system 130 and maintain the integrity of the separation between HAA 292 and reactor coolant system 130 during earthquake-related movement of isolation assembly 190. As an additional or alternative result, MIRSS assembly 200 is configured to improve maintenance access. For example, HAA 292 may be a congested zone with electrical cabinets, piping, and other objects within the area, and work to the support structure of isolator 150 and MIRSS assembly 200 may be performed below (e.g., below) HAA 292, remote from (e.g., spaced apart from) the congested zone.

[0099] Well seal 298 may be a flexible seal configured to maintain a seal between HAA 292 and riser annular gap 224 (and thus between HAA 292 and reactor coolant system 130) during movement of isolated MIRSS assembly 200 relative to, and independent of, non-isolated reactor building structures 102-1, 102-2 that at least partially define containment of HAA 292. As a result, HAA seal 294 and well seal 298 may be configured to collectively maintain a seal between HAA 292 and circuit 236 of reactor coolant system 130, thereby maintaining isolation of HAA 292 from reactor coolant system 130 and the air circulating therethrough.

[0100] In some demonstrative embodiments, the nuclear power plant 100 may be configured to contain radioactive material (e.g., radionuclides) within the HAA 292 of the reactor building 102, which may include radioactive material that may enter the HAA 292 from the reactor containment system 140 (e.g., from the primary vessel 146, the protective vessel 144, the reactor 142, and / or the head 148), material that may be introduced into the HAA 292 that is further inserted into the primary vessel 146, or any combination thereof. The HAA seals 294 and the well seals 298, individually or in combination with each other and at least with the cylindrical reactor support structure 202, may be configured to isolate and / or contain the HAA 292 from the circulation 236 of the reactor coolant system 130 (e.g., the inlet conduit 118, the downcomer annular gap 214, the riser annular gap 224, the exhaust duct 216, the non-isolated exhaust 120, etc.) and the air flowing therethrough. Thus, the HAA seal 294 and the well seal 298 may be configured to isolate the circulation path 236 and, therefore, the reactor cooling system 130 from radioactive material (e.g., radionuclides) that may be present within the HAA 292 and / or that may be contained within the HAA 292.

[0101] Additionally, in some exemplary embodiments, the HAA seal 294 and the well seal 298 are flexible seals and are configured to flex relative to, or independently of, the non-isolated reactor building structures 102-1, 102-2 that at least partially define the seal of the HAA 292 to maintain isolation of the reactor coolant system 130 and any circuits 236 therein from the HAA 292 during movement of the isolated MIRSS assembly 200 (e.g., during an earthquake). As a result, the MIRSS assembly 200, including the HAA seal 294 and well seal 298, is configured to improve the isolation and / or containment of radioactive material (e.g., radionuclides) in the HAA 292 during an earthquake-related event, thereby reducing, minimizing, or preventing the transfer of such radioactive material into the circuit 236 of the reactor coolant system 130, and potentially into the surrounding environment 123, during or due to an earthquake-related event (earthquake) that causes the seismically isolated MIRSS assembly 200 to move relative to or independently of the non-seismic isolated reactor building structures 102-1, 102-2. The HAA seal 294 and / or well seal 298 may be configured to flex relative to and independently of the non-isolated reactor building structures 102-1, 102-2 to maintain isolation of the reactor coolant system 130 and its circuits 236 from the HAA 292 before, during, and after movement of the isolated MIRSS assembly 200, during an earthquake-related event, after the conclusion of an earthquake-related event (e.g., immediately after the conclusion of an earthquake-related event), or before an earthquake-related event, etc., such that the HAA seal and well seal 298 may be configured collectively or independently to provide resilient isolation of the HAA 292 (and potentially radioactive material, such as radionuclides, therein) from the reactor coolant system 130 and any circuits 236 thereof.

[0102] In some exemplary embodiments, both HAA seal 294 and well seal 298 are flexible seals, although exemplary embodiments are not limited thereto. For example, in some exemplary embodiments, only HAA seal 294 or well seal 298 may be a flexible seal (e.g., comprising Inconel 625), while the other of HAA seal 294 or well seal 298 may be a rigid, non-flexible seal (e.g., comprising carbon steel).

[0103] In some exemplary embodiments, the MIRSS assembly 200 is configured to allow access to the isolators 150 for maintenance, inspection, and repair. This design includes a permanently installed track 152 and, in some exemplary embodiments, a mechanical lift for completing the replacement of the isolators 150. For example, as shown in FIGS. 1A-1H , the reactor building 102 may include a circumferential track 152 (e.g., a track including at least two parallel rails) extending at least circumferentially around the circular pattern of isolators 150 on the structural support surface 102-12 around the periphery of the MIRSS assembly 200. The track 152 may allow equipment to be easily moved around the MIRSS assembly 200 (e.g., on a trolley rolling on the track 152) to access, repair, and / or replace equipment at various azimuthal locations in the reactor building interior 108 below the HAA 292.

[0104] The track 152 may further extend out of the air intake conduit 118 through one or more openings 156, including a branch of the track extending through the non-vibration-isolated air intake conduit 116, through each opening 116-O in the non-vibration-isolated air intake conduit 116 to an opening 156 (e.g., a door, hatch, etc.) in a sidewall of the conduit 116 that allows for the transfer of equipment to and / or from the air intake conduit 118, for example, using a trolley (which may include a lift table) that may be configured to move on the track 152 via engaged rail wheels. The track 152 may allow an operator to access and replace the vibration isolator 150, which structurally supports at least a portion of the MIRSS assembly 200. For example, the portion of the MIRSS assembly 200 adjacent the isolator 150 may be pushed upward to reduce structural loads on the isolator 150, the isolator 150 may be removed (e.g., disconnecting the isolator 150 from the underlying building structure 102-1), the removed isolator 150 may be placed on a lift table of a trolley on the elevated track 152, and the lift table may then be lowered onto the trolley with the isolator 150. The trolley with the isolator 150 may then be moved to an access position at least partially around the intake conduit 118 on the track 152 where the isolator 150, either alone or together with the trolley, may be removed from the intake conduit 118. 1D , the trolley may also travel from the air inlet conduit 118 on a branch of the track 152 extending from the air inlet conduit 118, through one or more non-vibration-isolated air inlet conduits 116, to an opening 156 (e.g., a door, hatch, etc.), through a sidewall of the one or more non-vibration-isolated air inlet conduits 116, and out the circulation path 236 of the reactor coolant system 130. In another example, the trolley may travel on the track 152 extending through an opening (e.g., a door, hatch, etc.) in a bulkhead of the upper building structure 102-2 that at least partially defines the air inlet conduit 118.In another example, the trolley may be moved on the track 152 to a position axially (e.g., vertically) below a gap temporarily formed between the MIRSS assembly 200 and the upper building structure 102-2 based on at least partial removal of the HAA seal 294, and the vibration isolation device 150 may be lifted (alone or with the trolley) out of the intake conduit 118 and into the HAA 292 through the gap in the HAA seal 294. The replacement vibration isolator 150 may be introduced into the intake conduit 118 by the reverse process of removing the vibration isolator 150, such that the replacement vibration isolator 150 is moved on a trolley carried on a track 152 through the intake conduit 118 to the location where the removed vibration isolator 150 is to be removed, and the replacement vibration isolator 150 may be lifted and placed (e.g., via a lift table on a trolley) at the location where the removed vibration isolator 150 is to be removed, and at the same time, the MIRSS assembly 200 may be lowered to structurally support the MIRSS assembly 200 at least partially on the replacement vibration isolator 150. As a result, the track 152, in combination with the structure of the MIRSS assembly 200, may facilitate improved ease of maintenance of equipment at the nuclear power plant 100, allowing for improved access for maintenance to the isolator 150, and may also enable a low-cost lifting and handling system for accessing and handling the isolator and / or other equipment and structures of the MIRSS assembly 200 within the intake duct 118 without interfering with the densely packed HAA 292.

[0105] In some exemplary embodiments, the MIRSS assembly 200 is configured so that the inlet opening 216-O1 of the exhaust duct 216 can be positioned at the top 224-U of the riser annular gap 224 defined between the top 210-U of the collector cylinder 210 (also referred to herein as the top region, top, etc. of the collector cylinder 210), and thus the top 210-U of the collector cylinder 210 and the opposing top of the outer sidewall 140-S of the reactor containment system 140 (e.g., opposing tops of the outer sidewall 144-S of the protective vessel 144, or in exemplary embodiments where the reactor containment system 140 does not include any protective vessel, opposing tops of the outer sidewall of the primary vessel 146, etc.). The top 210-U of the collector cylinder 210 and the top 224-U of the riser annular gap 224 may each be at least partially defined as portions of the collector cylinder 210 and the riser annular gap 224 immediately adjacent their respective top edges defined radially outward by a structure (e.g., defined by an upper structural member 312 of an upper modular structure 310 of a MIRSS module 300 that at least partially defines the MIRSS assembly 200, as described herein). As a result, the MIRSS assembly 200 may induce the high-temperature working fluid 244 to flow out of the riser annular gap 224 from the top 224-U of the riser annular gap 224 by directing the high-temperature working fluid 244 to exit the riser annular gap 224 adjacent the top of the reactor containment system 140 (e.g., the top of the protective vessel 144), which is relatively close to the floor structure 290 and thus the reactor head access area (HAA) 292. In this manner, the MIRSS assembly 200 may be configured to reduce, minimize, or prevent the existence of a thermal "dead zone" of stagnant high-temperature working fluid 244 at the top 224-U of the riser annular gap 224, thereby improving cooling at the top of the reactor containment system 140 (e.g., the top of the protective vessel 144) and further improving cooling and heat removal within the reactor building 102.The MIRSS assembly 200 may be configured to define the exhaust duct 216 relative to the reactor containment system 140 (e.g., relative to at least the protective vessel 144) such that the inlet opening 216-O1 (also referred to herein as an exhaust duct inlet, exhaust duct inlet opening, etc.) is at or above the top of the reactor 142 and / or the top of at least the surface level of the working fluid in the primary vessel 146 (in a direction perpendicular to the grade 182). As a result, the MIRSS assembly 200 may be configured to remove heat from the high-temperature working fluid 244 by moving it vertically upward along the entire vertical height of the reactor 142, protective vessel 144, etc., ensuring cooling of the entire vertical height of the reactor 142, protective vessel 144, etc.

[0106] In some exemplary embodiments, a nuclear power plant may include a reactor coolant system that circulates a working fluid (e.g., air) through passageways, conduits, etc. to absorb heat rejected from the reactor. In some cases, when the reactor building structure (e.g., the superstructure or the entire reactor building) is seismically isolated by one or more isolators, the reactor coolant system circulates the working fluid away from the reactor containment system beneath the reactor building's concrete floor structure, which may be relatively thick, to provide at least partial structural support and / or containment for the reactor building and / or reactor containment system, which in turn may space the exhaust conduit vertically downward from the top of the reactor containment system, thereby reducing cooling of the top of the reactor containment system (e.g., at least its protective vessel). Additionally, the reactor coolant system exhaust may be contained within the reactor building's seismically isolated portion, increasing structural loads on the isolators.

[0107] In some demonstrative embodiments, the nuclear power plant 100 may include one or more earthquake-related damping mechanisms 158 configured to reduce, minimize, or prevent earthquake-induced relative movement of the isolation assemblies 190 relative to the isolators 150 and / or the reactor building 102. The one or more earthquake-related damping mechanisms 158 may reduce the rate of such earthquake-induced relative movement of the isolation assemblies 190, thereby further reducing displacement of the isolation assemblies 190 and reducing or preventing the risk of the isolation assemblies 190 contacting the structure of the reactor building 102 and / or reducing or preventing the risk of stresses (e.g., shear stresses) on the isolators 150 exceeding a threshold displacement or stress tolerance of the isolators 150. The one or more earthquake-related damping mechanisms 158 may be coupled to one or more isolators 150 (e.g., adjacent within the air inlet conduit 118), may be integrated with one or more isolators 150, or the like. The one or more earthquake-related damping mechanisms 158 may be, for example, shock absorbing devices. The one or more earthquake-related damping mechanisms 158 may be configured to act as shock absorbers to damp earthquake-induced relative movement of the isolation assembly 190 relative to the isolator 150 and / or the reactor building 102 .

[0108] As shown in FIGS. 1A-1H and 2A-2G, the cylindrical reactor support structure 202, the collector cylinder 210, and the gap 222 may each have a cylindrical shape, such that the cylindrical reactor support structure 202, the collector cylinder 210, and the bulkhead 222 may each have a circular cross-section. However, exemplary embodiments are not limited thereto. For example, in some exemplary embodiments, one or more of the cylindrical reactor support structure 202, the collector cylinder 210, or the bulkhead 222 may define a non-cylindrical shape having a non-circular cross-section. For example, one or more of the cylindrical reactor support structure 202, the collector cylinder 210, or the bulkhead 222 may define a polygonal prism shape having a polygonal cross-section. Such a polygon may be any polygon, including, for example, a square, a rectangle, a hexagon, a nonagon, a decagon, etc. However, it will be understood that the cylindrical reactor support structure 202, the collector cylinder 210, and the bulkhead 222 may independently have any shape.

[0109] 1A-1H , reactor containment system 140, including protective vessel 144, primary vessel 146, head 148, and reactor 142, is shown as having a circular cross-section in a horizontal plane, with protective vessel 144, primary vessel 146, and reactor 142 having cylindrical shapes and head 148 having a disk shape. However, it will be understood that exemplary embodiments are not limited thereto. For example, in some exemplary embodiments, one or more of protective vessel 144, primary vessel 146, head 148, or reactor 142 may have a non-circular cross-section in a horizontal plane, including a polygonal cross-section. Such a polygon may be any polygon, including, for example, a square, rectangle, hexagon, nonagon, decagon, etc. However, it will be understood that protective vessel 144, primary vessel 146, head 148, and reactor 142 may independently have any shape.

[0110] 3A and 3B are perspective views of a MIRSS module 300 according to some exemplary embodiments. FIG. 3C is a cross-sectional elevation view of the MIRSS module 300 of FIG. 3A along cross-sectional line IIIC-IIIC' of FIG. 3A according to some exemplary embodiments. FIG. 3D is a cross-sectional elevation view of the MIRSS module 300 of FIG. 3A along cross-sectional line IIID-IIID' of FIG. 3C according to some exemplary embodiments. FIG. 3E is a cross-sectional plan view of the MIRSS module 300 of FIG. 3A along cross-sectional line IIIE-IIIE' of FIG. 3D according to some exemplary embodiments. FIG. 3F is a cross-sectional plan view of the MIRSS module 300 of FIG. 3A along cross-sectional line IIIF-IIIF' of FIG. 3D according to some exemplary embodiments.

[0111] Figures 4A and 4B are perspective views of a MIRSS module 300 according to some exemplary embodiments. Figure 4C is a cross-sectional elevation view of the MIRSS module 300 of Figure 4A along cross-sectional line IVC-IVC' of Figure 4A according to some exemplary embodiments. Figure 4D is a cross-sectional elevation view of the MIRSS module of Figure 4A along cross-sectional line IVD-IVD' of Figure 4C according to some exemplary embodiments.

[0112] Figures 5A and 5B are perspective views of a MIRSS module 300 according to some exemplary embodiments. Figure 5C is a cross-sectional elevation view of the MIRSS module 300 of Figure 5A along cross-sectional line VC-VC' of Figure 5A according to some exemplary embodiments. Figure 5D is a cross-sectional elevation view of the MIRSS module of Figure 5A along cross-sectional line VD-VD' of Figure 5C according to some exemplary embodiments.

[0113] 3A-5D, and as further shown in FIGS. 1A-1F and 2A-2G, in some exemplary embodiments, MIRSS assembly 200 is comprised of modular units, referred to herein as MIRSS modules 300, which can be assembled (coupled together) to construct at least annular structure 230 of MIRSS assembly 200. MIRSS modules 300 can each be fabricated remotely (e.g., at a remote location) from the construction site of reactor building 102 (e.g., by conventional fabrication techniques), easily transported to the construction site of reactor building 102, and coupled together "on site" (e.g., at the construction site of reactor building 102) to construct MIRSS assembly 200 at least partially or entirely. The constructed MIRSS assembly 200 may then be installed, mounted, etc. in position on the seismic isolation device 150 on the lower building structure 102-1 (e.g., by being lowered at least partially into the storage pit 102-11) to establish the MIRSS assembly 200 as a seismic isolation structure.

[0114] 1A-2G and 3A-5D, MIRSS modules 300 may define separate azimuthal segments 230-A of annular structure 230, and multiple MIRSS modules 300 (e.g., the combination of MIRSS modules 300-1, 300-2, and 300-3 shown) may be azimuthally coupled together to at least partially construct MIRSS assembly 200, for example, by coupling together coupled opposite azimuthal edges 300-E of adjacent MIRSS modules 300. Adjacent azimuthal edges 300-E of adjacently coupled MIRSS modules 300 of MIRSS assembly 200 may be coupled together by various known processes, including welding, adhesive bonding, riveting, etc.

[0115] 2A-5D , each individual MIRSS module 300 may include an upper modular structure 310 and one or more lower modular structures 320 stacked axially below the upper modular structure 310. The upper modular structures 310 of the coupled MIRSS modules 300 may collectively define the cylindrical reactor support structure 202 of the MIRSS assembly 200. In other words, each individual upper modular structure 310 of each individual MIRSS module 300 may define a separate azimuthal portion of the cylindrical reactor support structure 202 and the collector cylinder 210, and each separate combination of the lower modular structures 320 of each individual MIRSS module 300 may define a separate azimuthal portion of the bulkhead 222. For example, each lower modular structure 320 of coupled MIRSS modules 300 may define a bulkhead 222 of MIRSS assembly 200 and, together with upper modular structure 310, may define collector cylinder 210 of MIRSS assembly 200. Additionally, as shown, structural members 302 (e.g., steel structural members) of MIRSS module 300, including structural members of MIRSS assembly 200, may be configured to define one or more shielded chambers 392 within MIRSS module 300 in which one or more shielding materials 390 may be provided and thus housed.

[0116] Additionally, the MIRSS modules 300 may be adjusted (e.g., scaled up or down in size) to accommodate different sized reactors, for example, by including or excluding certain structures that comprise the MIRSS modules 300 during fabrication to configure the MIRSS modules 300 and the resulting MIRSS assembly 200 upon coupling of such MIRSS modules 300. For example, different amounts of lower modular structures 320 may be axially stacked below each upper modular structure 310 of coupled MIRSS modules 300 of the MIRSS assembly 200 to adjust the axial height of the resulting MIRSS assembly 200. In other examples, the MIRSS modules 300 may include different amounts of azimuthal segments 300-A and / or different amounts of MIRSS modules 300 may be azimuthally coupled together to adjust the diameter of the collector cylinder 210 of the MIRSS assembly 200. Additionally, different MIRSS modules 300 that at least partially define different exhaust ducts 216 (e.g., at least openings 216-O1 and 216-O2 thereof), or a particular MIRSS module 300 that does not include same, may be coupled together to at least partially construct a MIRSS assembly 200 configured to define a particular arrangement and configuration of exhaust ducts 216 to direct high-temperature working fluid 244 to exit collector cylinder 210 and thus control the flow of working fluid within reactor coolant system 130. As a result, the MIRSS assembly 200 and its MIRSS modules 300 in some example embodiments are configured to provide increased flexibility to accommodate different sized reactors and different cooling system flow path configurations with reduced or minimized redesign thereof.

[0117] As shown, each MIRSS module 300 may have respective structural members 302 including upper structural member 312 including upper modular structure 310 and lower structural member 322 including lower modular structure 320, and may include a structural member defining an inner sidewall surface 354 that, when MIRSS modules 300 are coupled together, defines a collector cylinder 210 having an inner cylindrical surface 212. As shown, inner sidewall surface 354, including its upper and lower inner sidewall surfaces 354-U and 354-L, may be concave, such that collector cylinder 210 collectively defined by inner sidewall surfaces 354 of multiple coupled MIRSS modules 300 may have a cylindrical shape with a circular cross-section. Additionally, coupled MIRSS modules 300 each have structural members 302 defining outer sidewall surfaces 344 and outer sidewall surfaces 310-S that, when the MIRSS modules 300 are coupled together, collectively define bulkhead 222 having outer cylindrical surface 223 and outer sidewall surface 200-S of MIRSS assembly 200. As shown, outer sidewall surface 344 may be convex, and bulkhead 222 collectively defined by outer sidewall surfaces 344 of multiple coupled MIRSS modules 300 may have a cylindrical shape with a circular cross-section.

[0118] 3A-5D depict inner sidewall surface 354 and its upper and lower portions 354-U and 354-L as being concave, it will be understood that exemplary embodiments are not limited thereto. For example, in some exemplary embodiments, inner sidewall surface 354 (including its upper and lower inner sidewall surfaces 354-U and 354-L) may be a flat, planar surface, and collector cylinder 210 collectively defined by inner sidewall surfaces 354 of multiple coupled MIRSS modules 300 may have a polygonal prism shape having a polygonal cross-section with a number of sides corresponding to the number of flat, planar, "concave" surfaces 354 of the coupled MIRSS modules 300. Furthermore, while FIGS. 3A-5D depict outer sidewall surface 344 as being convex, it will be understood that exemplary embodiments are not limited thereto. For example, in some exemplary embodiments, the outer side wall surface 344 may be a flat, planar surface, and the partition 222 collectively defined by the outer side wall surfaces 344 of multiple MIRSS modules 300 connected together may have a polygonal prism shape having a polygonal cross section with a number (quantity) of sides corresponding to the number of flat, planar "convex" surfaces 344 of the MIRSS modules 300 connected together.

[0119] As shown, each upper modular structure 310 may include upper structural members 312, including, for example, metal plates, plate girders, plate steel, steel beams, I-beams, etc., that collectively and at least partially define the top 210-U of the collector cylinder 210 of the assembled MIRSS assembly 200, and thus at least partially define the top 224-U of the riser annular gap 224 defined between the MIRSS assembly 200 and the reactor containment system 140 supported thereby. The upper structural members 312 may further at least partially define an upper shielding chamber 316 within a containment section (e.g., cavity) defined by the upper structural members 312 that is configured to accommodate (e.g., hold, fill, etc.) an upper shielding material 318 (also referred to herein as first shielding material) therein. Such upper shielding material 318 may be provided (e.g., injected) into upper shielding chamber 316 (e.g., via an opening, hatch, etc. in upper surface 300-U of upper modular structure 310) after MIRSS modules 300 are coupled together to at least partially construct MIRSS assembly 200, which is then mounted on isolators 150 during construction of reactor building 102. As a result, the overall weight of MIRSS modules 300 and MIRSS assembly 200 may be reduced during the installation process. Such weight reduction may, in turn, simplify the fabrication, construction, and installation of cylindrical reactor support structure 202, collector cylinder 210, and bulkhead 222, and the shielding provided by the installed MIRSS assembly 200. Additionally, such weight reduction may result in reduced costs associated with fabricating, constructing, and installing the cylindrical reactor support structure 202, collector cylinders 210, and bulkheads 222, and the shielding provided by the installed MIRSS assembly 200. As shown, each upper modular structure 310 may define a separate upper shielded chamber 316 to include a region of the interior volume of the upper modular structure 310, excluding one or more exhaust ducts 216 extending through the interior volume.It will be understood that the upper shielded chamber 316 may comprise a cavity defined by the inner surface of one or more upper structural members 312 (e.g., beams, plates, girders, etc.) of the upper modular structure 310, alone or in combination with one or more duct structures (e.g., one or more exhaust duct structures 612) of the exhaust manifold structure 610 connected to the MIRSS module 300.

[0120] 1A-2G, and further shown in FIGS. 3A-F and 4A-4D, one or more MIRSS modules 300, and in particular, upper structural members 312 of one or more MIRSS modules 300, may be configured to at least partially define one or more exhaust ducts 216 of MIRSS assembly 200 extending between inlet opening 216-O1 of MIRSS module 300 and outlet opening 216-O2 of MIRSS module 300. For example, upper structural members 312 of one or more MIRSS modules 300 may define at least one or more inlet openings 216-O1 and one or more outlet openings 216-O2 of one or more exhaust ducts 216. The remaining structure of the one or more exhaust ducts 216 (e.g., one or more duct side walls extending between the inlet opening 216-O1 and the outlet opening 216-O2 through the interior of the upper module structure 310) may be further defined by a separate duct structure (e.g., exhaust duct structure 612 of the exhaust manifold structure 610) connected to the MIRSS module 300 and / or the annular structure 230 at least partially defined by the MIRSS module 300, such that the separate duct structure extends through the outlet opening 216-O2 to at least the inlet opening 216-O1, completing the definition of the exhaust duct 216 extending from the collector cylinder 210 through the interior 308 of the MIRSS module 300 (e.g., from the inlet opening 216-O1 to at least the outlet opening 216-O2). The inlet opening 216-O1 may be defined in an inner sidewall surface 354-U configured to define a portion of the top 210-U of the collector cylinder 210 and thus the top 224-U of the riser annular gap 224, and the outlet opening 216-O2 may be defined in a convex outer sidewall surface 310-S configured to define the outer sidewall surface 200-S of the MIRSS assembly 200 when the MIRSS modules 300 are coupled together. As a result, as shown in FIGS. 2A-2G , the MIRSS assembly 200 including the coupled MIRSS modules 300 may include multiple exhaust ducts 216 extending through each module interior 308 of each individual MIRSS module 300 between the top 210-U of the collector cylinder 210 and the outer sidewall surface 200-S of the MIRSS assembly 200.It will be understood that the collective module interiors 308 of MIRSS modules 300 coupled together to construct (e.g., establish, define, etc.) at least annular structure 230 may collectively, at least in part, define interior 218 of MIRSS assembly 200. Module interior 308 of each MIRSS module 300 may comprise one or more enclosures, cavities, etc. defined by the interior surfaces of one or more structural members 302, including one or more upper structural members 312 and / or one or more lower structural members 322 of MIRSS module 300, where one or more upper structural members 312 and / or one or more lower structural members 322 may each include beams, plates, girders, etc., which may be steel beams, steel plates, steel girders, etc.

[0121] 1A-2G, the exhaust duct 216 may further be at least partially defined by one or more exhaust duct structures 612 of one or more exhaust manifold structures 610 coupled with the annular structure 230 (e.g., the duct sidewalls of the exhaust duct 216 may be defined), such that the exhaust duct structure 612 extends through each of one or more internal spaces of the one or more upper modular structures 310 through at least one outlet opening 216-O2 to at least one inlet opening 216-O1, such that the inlet opening 610-O1 of the one or more exhaust duct structures 612 opens to the top 210-U of the collector cylinder 210 to receive the high-temperature working fluid 244 and direct the high-temperature working fluid 244 from the top 224-U of the riser annular gap 224 towards the surrounding environment 123 via at least the outlet opening 610-O2 of the exhaust manifold structure 610. However, it will be understood that in some exemplary embodiments, the upper structural member 312 defines an exhaust duct structure that completes the definition of the exhaust duct 216 through the module interior 308 of the MIRSS module 300 independent of any exhaust manifold structure 610 separate from the MIRSS module 300, such that the exhaust manifold structure 610 can be omitted from the MIRSS assembly 200.

[0122] 3A-3F and 4A-4D, some MIRSS modules 300-1 and 300-2 of MIRSS assembly 200 may include one or more openings 216-O1 and 216-O2 and thus at least partially define one or more exhaust ducts 216 extending therethrough between such openings 216-O1 and 216-O2. Referring to FIGS. 5A-5D, in some exemplary embodiments, one or more MIRSS modules 300-3 that comprise MIRSS assembly 200 may be configured such that openings 216-O1 and 216-O2 are omitted and thus do not define any exhaust ducts 216 extending therethrough.

[0123] Thus, when coupled together, different combinations of MIRSS modules 300 having upper modular structures 310 that may or may not at least partially define one or more exhaust ducts 216 may at least partially construct a MIRSS assembly 200 configured to include particular arrangements and / or combinations of exhaust ducts 216, and therefore configured to direct particular arrangements of working fluid 240 exiting riser annular gap 224 to control heat buildup within riser annular gap 224. Thus, the modular nature of MIRSS assembly 200, by coupling various MIRSS modules 300 that may include or exclude structures that at least partially define one or more exhaust ducts 216, allows for increased flexibility in the design and construction of MIRSS assembly 200 to provide particular and desired arrangements of exhaust flow paths exiting riser annular gap 224 from reactor containment system 140.

[0124] As shown at least in FIG. 2 and further shown in FIGS. 1A-1H, the upper structural member 312 of the upper modular structure 310, which at least partially defines the cylindrical reactor support structure 202 of the MIRSS assembly 200 when the MIRSS modules 300 are coupled together, may be configured to contact and structurally support at least one structural portion 140-P of the reactor containment system 140 (which may be part of the head 148, the primary vessel 146, and / or the protective vessel 144), and may be configured to rest on one or more seismic isolators 150 (e.g., at the bottom of the horizontal webbing, plate beam, steel plate, etc. of one or more plate beams of the structural member 302) so as to transfer at least a portion of the structural loads of the separate azimuthal segment 230-A and the reactor containment system 140 supported by the MIRSS assembly 200 to the at least one seismic isolator 150.

[0125] As shown, each lower modular structure 320 may include lower structural members 322, including, for example, metal plates, plate girders, plate steel, steel beams, I-beams, etc., that collectively and at least partially define the lower portion 210-L of the collector cylinder 210 of the assembled MIRSS assembly 200, and thus at least partially define the lower region 224-L of the riser annular gap 224 defined between the MIRSS assembly 200 and the reactor containment system 140 supported thereby. The lower portion 210-L of the collector cylinder 210 may be a portion of the collector cylinder 210 excluding its top 210-U, and the lower portion 224-L of the riser annular gap 224 may be a portion of the riser annular gap 224 excluding its top 224-U. The lower structural member 322 may at least partially define the downcomer annular gap 214 and the riser annular gap 224 at opposing sidewall surfaces 344 , 354 of the lower modular structure 320 .

[0126] Lower structural member 322 may further at least partially define one or more lower shielding chambers 326 configured to hold one or more lower shielding materials 328 therein. One or more lower shielding materials 328 housed in one or more lower shielding chambers 326 of lower modular structure 320 may comprise the same material or a different material than the upper shielding materials 318 housed in one or more upper shielding chambers 316 of upper modular structure 310. For example, the lower structural members 322 of the multiple lower modular structures 320 in a given MIRSS module 300 may define an inner lower shielding chamber 326-1 that may extend axially between and / or through the multiple axially stacked (e.g., vertically stacked) lower modular structures 320, and the inner lower shielding chamber 326-1 may house a first lower shielding material 328-1 that may include any heat shielding material that may be configured to provide heat insulation, including a thermal expansion break between the riser pipe annular gap 224 and the downcomer pipe annular gap 214, for example, as described herein, to improve the performance of the reactor cooling system 130 including such downcomer pipe and riser pipe annular gaps 214 and 224. In another example, the lower structural members 322 of the multiple lower module structures 320 in a given MIRSS module 300 may define one or more outer lower shielding chambers 326-2 radially disposed between the inner lower shielding chamber 326-1 and the outer side wall surface 344 that at least partially defines the bulkhead 222, and if the one or more outer lower shielding chambers 326-2 house a second lower shielding material 328-2, this may be a radiation shielding material configured to provide radiological shielding to one or more spaces, structures, etc. outside the constructed MIRSS assembly 200.

[0127] In some exemplary embodiments, a first lower shield 328-1 (e.g., a heat shield) may be installed in one or more first lower shield chambers 326-1 within a MIRSS module 300 during fabrication of the MIRSS module 300 (e.g., as part of the load-bearing structure of the MIRSS module 300 or independently thereof) prior to coupling the MIRSS modules 300 together to at least partially construct the MIRSS assembly 200. For example, one or more MIRSS modules 300 may include a first lower shield 328-1 (also referred to herein as a second shield) in the inner lower shield chamber 326-1, and the outer lower shield chamber 326-2 may be empty and devoid of shielding, prior to coupling multiple MIRSS modules 300 together to form at least a portion of the MIRSS assembly 200 shown in FIGS. 1A-1H and 2A-2H. Such first lower shielding material 328-1 may include any heat shielding material, including, for example, one or more BTU-BOARD® panels, one or more vacuum panels, etc., that may occupy (partially or entirely) the shielded chamber 326-1.

[0128] In some exemplary embodiments, the outer lower shielding chamber 326-2 may be initially empty within an independently fabricated MIRSS module 300 prior to the MIRSS modules 300 being coupled together to at least partially construct the MIRSS assembly 200. A second lower shielding material 328-2 (e.g., a radiation shielding material) may be provided within one or more second shielding chambers 326-2 of one or more MIRSS modules 300 after the MIRSS modules 300 have been coupled together to at least partially construct the MIRSS assembly 200 and after the MIRSS assembly 200 has been mounted on the seismic isolators 150 of the reactor building 102 under construction, such that the second lower shielding material 328-2 (also referred to herein as third shielding material) may be provided within the second shielding chamber 326-2 while the MIRSS assembly 200 is already resting on the seismic isolators 150 within the reactor building 102. As a result, the fabricated MIRSS modules 300 may be lighter (e.g., may have reduced weight) due to the absence of the second lower shielding material 328-2 during the initial fabrication of the MIRSS modules 300 and during their connection to at least partially construct the MIRSS assembly 200, which may simplify and reduce the cost of fabricating, transporting, and connecting the MIRSS modules 300 to at least partially construct the MIRSS assembly 200, and may further simplify and reduce the cost of constructing the MIRSS assembly 200 and installing it on the vibration isolation device 150.

[0129] As shown in Figures 1A-1H, the shielded chamber 296 of the MIRSS assembly 200 may be filled with various shielding materials 390 when the nuclear power plant 100 is completed, in which case one or more upper shielding materials 318 occupy the collective upper shielded chamber 316 of the MIRSS module 300 that includes the MIRSS assembly 200, a second shielding material 328-1 occupies the collective lower inner shielded chamber 326-1 of the MIRSS module 300 that includes the MIRSS assembly 200, and a third shielding chamber 328-2 occupies the collective lower outer shielded chamber 326-2 of the MIRSS module 300 that includes the MIRSS assembly 200. As shown in Figures 2A-2G, the MIRSS assembly 200 may omit at least a portion of the shielding material 390 prior to installation (e.g., mounting) of the MIRSS assembly 200 on the isolator 150, and such shielding material 390 may be provided within one or more shielded chambers 296 after the MIRSS assembly 200 is mounted on the isolator 150 to reduce the weight of the MIRSS assembly 200 during mounting of the isolator, and thus to reduce the cost and / or complexity of the construction process including such mounting.

[0130] As shown in Figures 1A-1H and 2A-2G, the MIRSS assembly 200 according to some exemplary embodiments is configured to define at least one shielded chamber 296 (e.g., at least one of the upper shielded chamber 316, the first lower shielded chamber 326-1, and / or the second lower shielded chamber 326-1 of one or more MIRSS modules 300 that comprise the MIRSS assembly 200) within the interior 218 of the MIRSS assembly 200 and radially outward from the collector cylinder 210, where the at least one shielded chamber 296 is configured to hold at least one shielding material (e.g., one or more of the upper shielding material 318, the first lower shielding material 328-1, or the second lower shielding material 328-2), although it will be understood that exemplary embodiments are not limited thereto. For example, in some exemplary embodiments, MIRSS assembly 200 (and in some embodiments, MIRSS module 300 including MIRSS assembly 200) may entirely omit any shielded chamber 296 and / or shielding material 390, and reactor building 102 may include one or more shielding materials external to MIRSS assembly 200 and may be configured to provide shielding to one or more spaces, structures, and / or equipment located external to MIRSS assembly 200 and / or isolation assembly 190.

[0131] 2A-2G, 3A-3F, 4A-4D, and 5A-5D, the MIRSS assembly 200 may include multiple different MIRSS modules 300, including four first MIRSS modules 300-1, four second MIRSS modules 300-2, and two third MIRSS modules 300-3, in which case the first to third MIRSS modules 300-1 to 300-3 may each have a common vertical height and angular sizes that are several times the basic azimuthal size and define angular sizes 300-1A, 300-2A, and 300-3A, and may be configured to be azimuthally connected together despite having different structures, to configure the MIRSS assembly 200 to include different arrangements such as different heights and / or diameters of the exhaust duct 216. Different MIRSS modules 300 may include different azimuthal (e.g., angular) sizes based on including different amounts of azimuthal segments 300-A having the same azimuthal size, which may include different structural members 302 that may include or omit one or more exhaust ducts 216 within the different MIRSS modules 300.

[0132] For example, as shown in Figures 3A to 3F, the first MIRSS module 300-1 defines two azimuth segments 300-A that are azimuthally adjacent to each other and independently define separate arcs having a first angle, such that the two combined azimuth segments 300-A of the first MIRSS module 300-1 define an arc having an angle size of 300-1A, in which case each of the azimuth segments 300-A defines a separate exhaust duct 216, thereby allowing the first MIRSS module 300-1 to at least partially define multiple (e.g., at least two) exhaust ducts 216. Conversely, as shown in Figures 4A to 4D and 5A to 5D, the second and third MIRSS modules 300-2 and 300-3 each define one azimuth angle segment 300-A that defines a separate arc having respective angular sizes 300-2A and 300-3A (which may be the same angular size as angular size 300-1A and half the angular size), in which case the second MIRSS module 300-2 at least partially defines a single exhaust duct 216, and the third MIRSS module 300-3 does not define any exhaust duct 216 (e.g., has no openings 216-O1 or 216-O2). Different combinations of the first through third MIRSS modules 300-1 through 300-3 may define MIRSS modules 300 having various arrangements of exhaust ducts 216 configured to define different specific exhaust flow paths exiting the collector cylinder 210, and may further define different diameters of the collector cylinder 210, and thus the diameter of the reactor containment system 140 (e.g., diameters of the protective vessel 144, primary vessel 146, etc.) that may be supported by the MIRSS assembly 200 within the collector cylinder 210.

[0133] As shown in Figures 1A-1H and 2A-2G, the MIRSS modules 300 coupled together to define at least the annular structure 230 of the MIRSS assembly 200 may collectively define a cylindrical reactor support structure 202 of the MIRSS assembly 200 configured to structurally support the reactor containment system 140 on a plurality of isolators 150, such that the MIRSS assembly 200 defines a seismic isolation assembly 190 within the nuclear power plant 100 that includes the reactor containment system 140 and is seismically isolated from the reactor building 102. Additionally, the MIRSS assemblies 300 coupled together to define at least the annular structure 230 of the MIRSS assembly 200 may collectively define the collector cylinder 210 of the MIRSS assembly 200, where the collector cylinder 210 is configured to at least partially receive the reactor containment system 140 (e.g., receive at least the protective vessel 144) based on the reactor containment system 140 being structurally supported by the cylindrical reactor support structure 202, such that the collector cylinder 210 is configured to at least partially define a riser annular gap 224 between the inner cylindrical surface 212 of the collector cylinder 210 and the outer sidewall surface 140-S of the reactor containment system 140 (e.g., the outer sidewall surface 144-S of the protective vessel 144, or, if the reactor containment system 140 does not include any protective vessel, the outer sidewall surface of the primary vessel 146, etc.). Additionally, the MIRSS modules 300 coupled together to define at least the annular structure 230 of the MIRSS assembly 200 may collectively define the bulkheads 222 of the MIRSS assembly 200, where the bulkheads 222 are configured to at least partially define downcomer pipe annular gaps 214 between the outer cylindrical surface 223 of the bulkheads 222 and the reactor building 102, and where the bottom opening 214-B of each pipe annular gap 214 is in fluid communication with the bottom opening 224-B of the riser pipe annular gap 224.Additionally, the MIRSS modules 300, which are connected together to define at least the annular structure 230 of the MIRSS assembly 200, may collectively and at least partially define a plurality of exhaust ducts 216 extending from the collector cylinder 210 through the interior 204 of the cylindrical reactor support structure 202 (e.g., extending to the outer sidewall surface 200-S of the MIRSS assembly 200 opposite the inner cylindrical surface 212 of the collector cylinder 210).

[0134] As shown in Figures 1A-1H, 2A-2G, and 3A-5D, it will be understood that because the MIRSS modules 300 are connected together (e.g., connected together between the azimuthal edges 300-E of adjacent MIRSS modules 300) to collectively define at least the annular structure 230 of the MIRSS assembly 200, the MIRSS modules 300 of the MIRSS assembly 200 define at least separate azimuthal segments 230-A of the annular structure 230, such that each MIRSS module 300 of the MIRSS modules 300 defining the annular structure 230 can define a separate azimuthal segment 202-A of the cylindrical reactor support structure 202, a separate azimuthal segment 210-A of the collector cylinder 210, and a separate azimuthal segment 222-A of the bulkhead 222. Further, as shown in at least Figures 1A-1H, 2A-2G, and 3A-5D, in each MIRSS module 300 of the multiple MIRSS modules 300 defining the annular structure 230, the upper modular structure 310 of the MIRSS module 300 defines each separate azimuthal segment 202-A of the cylindrical reactor support structure 202, such that when connected together, the upper modular structures 310 of the MIRSS modules 300 defining the annular structure 230 of the MIRSS assembly 200 collectively define the cylindrical reactor support structure 202, and the interiors (including the upper shielded chambers 316) of the upper modular structures 310 of the connected MIRSS modules 300 collectively define the interiors 204 of the cylindrical reactor support structure 202. The upper modular structure 310 of each such MIRSS module 300 may or may not at least partially define at least one exhaust duct 216 of the plurality of exhaust ducts 216 of the MIRSS assembly 200 .Additionally, as shown in at least Figures 1A to 1H, 2A to 2G, and 3A to 5D, in each MIRSS module 300 among the MIRSS modules 300 defining the annular structure 230, one or more lower module structures 320 axially stacked below the upper module structure 310 of the MIRSS module 300 collectively define a separate azimuthal segment 222-A of the partition wall 222 of the MIRSS assembly 200, and the upper module structure 310 of the MIRSS module 300 and these one or more lower module structures 320 can collectively define a separate azimuthal segment 210-A of the collector cylinder 210 of the MIRSS assembly 200. As further shown, each separate upper module structure 310 may define a separate upper surface 300-U of a MIRSS module 300 and / or may define an azimuthal section of the upper surface 200-U of the MIRSS assembly 200, such that each upper surface 300-U of the coupled MIRSS modules 300 of the MIRSS assembly 200 may collectively define the upper surface 200-U of the MIRSS assembly 200.

[0135] As shown in Figures 3A to 3F, 4A to 4D, and 5A to 5D, in each MIRSS module 300 among the multiple connected MIRSS modules 300 of the annular structure 230 of the MIRSS assembly 200, where each MIRSS module 300 comprises an upper modular structure 310 and one or more lower modular structures 320 stacked axially below the upper modular structure 310, these one or more lower modular structures 320 may collectively define an outer sidewall surface 344 that defines a separate azimuthal segment 222-A of the partition wall 222 of the annular structure 230, and the upper modular structure 310 and the one or more lower modular structures 320 may have respective inner sidewall surfaces 354-U and 354-L that collectively define a separate azimuthal segment 210-A of the collector cylinder 210 of the annular structure 230.

[0136] As shown, each separate azimuthal segment 210-A of the collector cylinder 210 defined by a separate MIRSS module 300 may be configured to at least partially define a separate azimuthal segment 224-A of the riser annular gap 224 between the inner sidewall surface 354 that at least partially defines the separate azimuthal segment 210-A of the collector cylinder 210 and an opposing azimuthal segment of the outer sidewall surface 144-S of the reactor containment system 140, which may be the outer sidewall surface 144-S of the protective vessel 144 or, in an exemplary embodiment in which the reactor containment system 140 does not include any protective vessel, etc., the outer sidewall surface of the primary vessel 146. In other words, in a MIRSS assembly 200 that structurally supports the reactor containment system 140 such that the reactor containment system 140 and the collector cylinder 210 collectively and at least partially define the riser annular gap 224, each azimuthal segment 210-A of the collector cylinder 210 defined by each MIRSS module 300 of the MIRSS assembly 200 can at least partially define a separate azimuthal segment 224-A that collectively defines the riser annular gap 224 that is at least partially defined between the collector cylinder 210 and the reactor containment system 140. As further illustrated, each separate azimuthal segment 222-A of the partition wall 222 defined by a separate MIRSS module 300 may be configured to at least partially define a separate azimuthal segment 214-A of the downcomer annular gap 214 between the outer sidewall surface 344 that at least partially defines the separate azimuthal segment 222-A of the partition wall 222 and an opposing azimuthal segment of the reactor building 102 (e.g., the inner containment pit surface 102-11S of the containment pit 102-11).In other words, in a MIRSS assembly 200 that is structurally supported and seismically isolated from the reactor building 102, such that the bulkhead 222 of the MIRSS assembly 200 and the reactor 102 (e.g., containment pit 102-11) collectively and at least partially define the downcomer annular gap 214, each azimuthal segment 222-A of the bulkhead 222 defined by each MIRSS module 300 of the MIRSS assembly 200 may at least partially define a respective separate azimuthal segment 214-A that collectively defines the downcomer annular gap 214 that is at least partially defined between the bulkhead 222 and the reactor building 102.

[0137] The MIRSS modules 300 described in any of the exemplary embodiments may be fabricated away from the reactor building 102 construction site (e.g., fabricated at one or more remote locations) based on the implementation of conventional fabrication techniques (e.g., welding, cutting, riveting, etc. of steel structural members 302, which may be plate girders, plate steel, steel beams, I-beams, etc.), and can be easily transported (together or separately) to the reactor building 102 construction site for assembly by connecting the MIRSS modules 300 together (e.g., by connecting opposite azimuthal edges 300-E of separate adjacent MIRSS modules 300 by welding, riveting, joining, etc.).

[0138] The modular configuration of the MIRSS assembly 200 via the linked MIRSS modules 300 may be configured to simplify overall project construction and fabrication of the nuclear power plant 100, particularly the construction of structures for structurally supporting and isolating the reactor containment system 140 and defining the air flow paths for the reactor coolant system 130. Fabricating such structures (e.g., MIRSS modules 300) on-site can be complex. For example, fabricating such structures on-site may involve isolating certain materials used in the construction of such structures from other materials used in the construction of other portions of the reactor building 102, for example, to protect the separate materials from contamination. In some exemplary embodiments, the MIRSS modules 300 that are connected together to at least partially construct the MIRSS assembly 200 may further be fabricated off-site (e.g., at one or more remote locations outside the nuclear power plant 100), transported together or separately to the reactor building 102 construction site at the nuclear power plant 100, and then connected together at the construction site (e.g., adjacent to where the reactor building 102 is being constructed) to construct at least a portion of the MIRSS assembly 200, which may then be installed (e.g., mounted) on the isolator 150 as a single-piece structure (e.g., by lifting the connected annular structure 230 and lowering it onto the isolator 150 via the operation of one or more cranes). The structures of the MIRSS assembly 200 (e.g., MIRSS modules 300, exhaust manifold structure 610, etc.) may be fabricated off-site, and then the fabricated structures may be transported to the construction site of the reactor building 102 for connection together and installation of the constructed MIRSS assembly 200 on the isolators 150 as a single piece structure, thereby reducing costs associated with construction area logistics / labor maintenance at the construction site of the reactor building 102. The modular design of the MIRSS assembly 200, based at least in part on connection together of MIRSS modules 300, may allow for flexible and conventional manufacturing methods for the MIRSS modules.For example, the MIRSS module 300 may utilize a plate-beam design for the structural members 302 that allows for the use of water jet, plasma cutter, or laser cutting operations to facilitate the fabrication of the structural members 302 of the MIRSS module 300 and the assembly of such structural members 302 to the MIRSS module 300 itself (e.g., using welding of the structural members 302 using one or more fixtures). It will be appreciated that the upper and lower modular structures 310 and 320 of the MIRSS module 300 may be connected together to form the MIRSS module 300 by connecting together the respective upper and lower structural members 312 and 322 of the upper modular structure 310 and the uppermost lower modular structure 320, and further connecting together the respective lower structural members 322 of axially adjacent lower modular structures 320 by known processes, including welding, riveting, etc. In some exemplary embodiments, the separate upper and lower module structures 310 and 320 of a given MIRSS module 300 may be fabricated independently and then coupled together to form the given MIRSS module 300.

[0139] MIRSS assembly 200, including MIRSS modules 300 coupled together to at least partially define annular structure 230 of MIRSS assembly 200, may be configured to simplify construction techniques used in the construction of nuclear power plant 100 and may further be configured to allow flexibility in fabrication techniques and placement of the structure, shielding, and conduits of MIRSS assembly 200. In some exemplary embodiments, when MIRSS assembly 200 includes MIRSS modules 300 (alone or in combination with exhaust manifold structure 610) that may be fabricated remotely at various locations and then transported to the reactor building construction site and coupled together to construct MIRSS assembly 200, MIRSS assembly 200 may be configured to be fabricated asynchronously with respect to other structures included in reactor building 102, which may reduce, minimize, or prevent construction bottleneck concerns in the construction of reactor building 102. Additionally, the MIRSS assembly 200 may be configured to reduce seismic design requirements for the entire reactor containment system 140, thereby enabling significantly more economical structural designs for some of the most expensive equipment required for the nuclear power plant 100. The MIRSS assembly 200 may allow for more compact placement of equipment within the reactor building 102, reducing civil engineering costs based on reduced excavation, backfill, and concrete pouring requirements.

[0140] 3A-5D each depict MIRSS module 300 including at least one upper modular structure 310 and one or more lower modular structures 320 axially stacked therebelow, it will be understood that exemplary embodiments are not limited in this respect. For example, in some exemplary embodiments, MIRSS module 300 may be constructed as a single piece structure instead of including separate upper and / or lower modular structures 310 and / or 320.

[0141] 3A-5D show MIRSS modules 300 including azimuthal segments 230-A of annular structures 230, each including an upper modular structure 310 and one or more axially stacked lower modular structures 320, with multiple such MIRSS modules 300 azimuthally connected together to construct annular structure 230 and thus at least partially construct MIRSS assembly 200, although it will be understood that exemplary embodiments are not limited thereto. For example, in some exemplary embodiments, the MIRSS module 300 may include separate upper modular structures 310 and lower modular structures 320 that can be fabricated independently at one or more sites (e.g., one or more remote locations remote from the construction site of the reactor building 102) and transported independently or together (without being connected together) to the construction site of the reactor building 102, and the MIRSS assembly 200 may be constructed by axially connecting and connecting separate groups (e.g., rings) of the lower modular structures 320 atop each other, and then connecting the upper modular structures 310 (e.g., individually or as an constructed cylindrical reactor support structure 202) onto the connected set (e.g., ring) of the lower modular structures 320 to construct at least the annular structure 230 and at least partially construct the MIRSS assembly 200.

[0142] 1A-2G depict MIRSS assembly 200 including multiple MIRSS modules 300 coupled together to collectively define annular structure 230, thereby at least partially defining MIRSS assembly 200, but it will be understood that example embodiments are not limited in this regard. For example, in some example embodiments, MIRSS assembly 200 shown in FIGS. 1A-2G may be a non-modular isolated reactor support system (IRSS) that is constructed at least partially as a single-piece structure, instead of being constructed based on coupling multiple MIRSS modules 300 together. As a result, in some example embodiments, MIRSS assembly 200 shown in FIGS. 1A-2G may be a non-modular isolated reactor support system (IRSS) that includes collector cylinder 210, cylindrical reactor support structure 202, bulkhead 222, and one or more exhaust ducts 216 (which, in some example embodiments, further include one or more shielded chambers 296), and may not include any MIRSS modules 300. In some exemplary embodiments, the MIRSS assembly 200 may be a non-modular isolated reactor support system (IRSS) that is constructed at least partially within the construction site of the reactor building 102, for example, on the lower building 102-1 and at least partially within the containment pit 102-11, rather than by separately fabricating and connecting together separate MIRSS modules 300.

[0143] 6A and 6B are perspective views of a MIRSS exhaust manifold structure 610 according to some exemplary embodiments. FIG. 6C is a cross-sectional perspective view of the MIRSS exhaust manifold structure 610 of FIG. 6A taken along cross-sectional line VIC-VIC′ of FIG. 6A according to some exemplary embodiments.

[0144] 6A-6C, and with further reference to FIGS. 1A-1H and 2A-2G, the MIRSS assembly 200 may include one or more exhaust manifold structures 610 including at least one exhaust duct structure 612 having a first opening 610-O1 and coupled to at least one outlet duct 614 having a second opening 610-O2. The one or more exhaust manifold structures 610 may be coupled to the annular structure 230 (e.g., to one or more MIRSS modules 300, the cylindrical reactor support structure 202, etc.) such that, for example, the one or more exhaust duct structures 612 of the exhaust manifold structure 610 extend through the interior 218 of the MIRSS assembly 200 (e.g., through one or more outlet openings 216-O2 to at least one or more respective inlet openings 216-O1), and the inlet openings 610-O1 defined by the one or more exhaust duct structures 612 are coupled to the annular structure 230 of the MIRSS assembly 200. The exhaust manifold structure 610 may be configured to open to (e.g., extend toward and / or into) the collector cylinder 210 defined by the collector cylinder 210 and, in turn, open to an elevated annular gap 224 defined between the collector cylinder 210 and an outer sidewall surface 140-S of the reactor containment system 140 (e.g., an outer sidewall surface 144-S of the protective vessel 144, an outer sidewall surface of the primary vessel 146 in exemplary embodiments in which the reactor containment system 140 does not include any protective vessel, etc.) when the reactor containment system 140 is coupled to the MIRSS assembly 200. Accordingly, the exhaust duct structure 612 of the exhaust manifold structure 610 may define one or more duct sidewalls of the exhaust duct 216. As a result, the one or more exhaust ducts 216 of the MIRSS assembly 200 may be at least partially defined by at least one or more exhaust duct structures 612 of the one or more exhaust manifold structures 610.

[0145] 1A-2G , exhaust manifold structure 610 may be coupled to annular structure 230 such that at least one exhaust duct structure 612 of exhaust manifold structure 610 may at least partially define upper shielded chamber 316 in MIRSS assembly 200. As a result, upper shielding material 318 may be supplied (e.g., injected) into upper shielded chamber 316 to fill the chamber, while exhaust duct 216 defined by upper structural member 312 of upper modular structure 310 and at least exhaust duct structure 612 of exhaust manifold structure 610 may allow working fluid 240 to flow out of riser excess gap 224 through exhaust manifold structure 610 to the exterior of MIRSS assembly 200 while maintaining isolation from upper shielding material 318.

[0146] 1A-1H, the exhaust manifold structure 610 may be considered part of the constructed MIRSS assembly 200, may be considered part of the vibration isolation assembly 190, and may thus be included in the vibration-isolated exhaust section 232 of the reactor cooling system 130. The exhaust manifold structure 610 may be configured to be coupled at each second opening 610-O2 thereof to a respective opening 126-O1 of each non-vibration-isolated exhaust conduit 126.

[0147] As further shown, a second opening 610-O2 of the exhaust manifold structure 610 may be coupled to a flexible duct 620 configured to couple therebetween to establish fluid communication between the opposing openings 610-O2 and 126-O1 of the exhaust manifold structure 610 and the non-isolated exhaust conduit 126, thereby maintaining the integrity of the reactor coolant system circuit 236 during movement of the isolation assembly 190 with the isolated exhaust section 232, independent of the reactor building 102 and the non-isolated exhaust section 120. In some exemplary embodiments, the one or more flexible ducts 620 may be considered part of the MIRSS assembly 200, although exemplary embodiments are not limited thereto. In some exemplary embodiments, the one or more flexible ducts 620 may be considered external to the MIRSS assembly 200.

[0148] As shown, in some exemplary embodiments, exhaust manifold structure 610 may include one or more exhaust duct structures 612 configured to at least partially define (e.g., define one or more duct sidewalls of) one or more exhaust ducts 216 of MIRSS assembly 200. Exhaust manifold structure 610 may further include an exhaust duct 614 configured to be coupled with non-vibration-isolated exhaust conduit 126, and thus configured to be coupled between one or more exhaust ducts 216 (defined at least in part by one or more exhaust duct structures 612) and flexible duct 620, thereby directing high-temperature working fluid 244 from exhaust manifold structure 610 into non-vibration-isolated exhaust section 120 of reactor coolant system 130. As shown, the exhaust manifold structure 610 may include at least two exhaust duct structures 612 connected in parallel to the exhaust outlet duct 614 via collector ducts 616, such that the exhaust manifold structure 610 at least partially defines at least two exhaust ducts 216 connected in parallel to the exhaust outlet duct 614, although exemplary embodiments are not limited thereto.

[0149] 1A-1G, 2A-2F, and 6A-6C, in some exemplary embodiments, an exhaust manifold assembly 600 includes an exhaust manifold structure 610, a flexible duct 620, and a non-vibration-isolating exhaust conduit 126 coupled together as a single assembly. As shown, one or more first openings 610-O1 of the exhaust manifold structure 610 may define a first opening 600-O1 of the exhaust manifold assembly 600, and an opposing opening 126-O2 of the conduit 126 from the first opening 126-O1 connected to the flexible duct 620 may define a second opening 600-O2 of the exhaust manifold assembly 600. An exhaust manifold assembly 600 including a connected exhaust manifold structure 610, flexible duct 620, and non-vibration-isolated exhaust conduit 126 may be connected to one or more MIRSS modules 300 and / or MIRSS assemblies 200 to include the exhaust manifold structure 610 in the MIRSS assembly 200, while the non-vibration-isolated exhaust conduit 126 may be connected to one or more separate non-vibration-isolated portions of the reactor building structure and / or reactor coolant system 130 (e.g., to the non-vibration-isolated exhaust portion 126).

[0150] In some exemplary embodiments, the exhaust manifold assembly 600 may omit the non-vibration-isolated exhaust conduit 126, and the exhaust manifold assembly 600 that may be coupled to the MIRSS module 300 and / or the MIRSS assembly 200 may include an exhaust manifold structure 610 and a flexible duct 620 coupled thereto at an exposed opening 620-O of the flexible duct 620. The exposed opening 620-O of the flexible duct 620 may then be connected to the non-vibration-isolated exhaust duct 126 of the non-vibration-isolated exhaust section 120 of the reactor cooling system 130 after the exhaust manifold assembly 600 is connected to the MIRSS module 300 and / or the MIRSS assembly 200 (e.g., after the MIRSS assembly 200 is mounted to the vibration isolation device 150 on the lower structure 102-1 so that the exposed opening of the flexible duct 620 may be connected to the non-vibration-isolated exhaust duct 126 as part of further construction after such mounting is performed as part of the completion of the reactor structure 102).

[0151] The flexible duct 620 may include bellows, flexible seals, expandable seals, etc. configured to flex (e.g., resiliently flex) in response to movement of the exhaust manifold structure 610 relative to the non-isolated exhaust conduit 126 without compromising the sealing of the flow path extending through the flexible duct 620 between the exhaust manifold structure 610 and the non-isolated exhaust conduit 126, thereby maintaining the integrity of the reactor coolant system circuit 236 during movement of the isolation assembly 190 with the isolated exhaust 232, independent of the reactor building 102 and the non-isolated exhaust 120. The flexible duct 620, according to some exemplary embodiments, may comprise (in part or in whole) a flexible material, such as Inconel 625, Inconel 718, stainless steel 316, stainless steel 304, a fluoroelastomer material (which may also be referred to as a fluoroelastomer seal), a fluorocarbon elastomer (FKM) polymer material, etc.

[0152] In some exemplary embodiments, exhaust manifold assembly 600 may omit both non-vibration-isolated exhaust conduit 126 and flexible duct 620, such that exhaust manifold assembly 600 becomes exhaust manifold structure 610. Exhaust manifold structure 610 may be coupled to one or more MIRSS modules 300 and / or a MIRSS assembly 200 including multiple linked MIRSS modules 300 while outlet opening 610-O2 of exhaust manifold structure 610 is exposed. Exposed opening 610-O2 may be coupled to flexible duct 620, which may be coupled to non-vibration-isolated exhaust conduit 126 after exhaust manifold structure 610 is coupled to one or more MIRSS modules 300 and / or a MIRSS assembly 200 including multiple linked MIRSS modules 300.

[0153] 6A-6C , in some exemplary embodiments, an exhaust manifold structure 610 may include a plurality of exhaust duct structures 612 that may be configured to extend through each separate outlet opening 216-O2 of one or more MIRSS modules 300 and further to each separate inlet opening 216-O1 to at least partially define each separate exhaust duct 216. The multiple exhaust duct structures 612 may be coupled in parallel with an outlet duct 614 of the exhaust manifold structure 610 via a collector duct 616. As a result, as shown in FIG. 2D , for example, a single exhaust manifold structure 610 may at least partially define multiple azimuthally spaced-apart separate exhaust ducts 216.

[0154] 6A-6C includes four separate exhaust duct structures 612 coupled in parallel to the outlet duct 614 via a collector duct 616, it will be understood that the exhaust manifold structure 610 may include a different amount of exhaust duct structures 612 configured to at least partially define a different amount of exhaust ducts 216. For example, the exhaust manifold structure 610 may include any amount of separate exhaust duct structures 612 coupled in parallel to the outlet duct 614 via a collector duct 616, including two separate exhaust duct structures 612, three separate exhaust duct structures 612, five separate exhaust duct structures 612, etc. In other examples, the exhaust manifold structure 610 may include a single exhaust duct structure 612 coupled in series to the outlet duct 614, in which case the collector duct 616 is omitted from the exhaust manifold structure 610. In some exemplary embodiments, the exhaust manifold structure 610 may include a single duct structure defining both a single exhaust duct structure 612 and a single outlet duct 614 connected in series.

[0155] 6A-6C, and also as shown in FIGS. 1A-1H and 2A-2G, the exhaust duct structure 612, the outlet duct 614, and the collector duct 616 of the exhaust manifold structure 610 may each have a circular cross-section, such that the exhaust duct structure 612, the outlet duct 614, and the collector duct 616 may be considered cylindrical ducts, and one or more exhaust ducts 216 may be at least partially defined as cylindrical ducts having one or more cylindrical duct sidewalls with circular cross-sections. However, exemplary embodiments are not limited thereto, and in some exemplary embodiments, the exhaust duct structure 612, the outlet duct 614, and the collector duct 616 may each independently have a cylindrical shape having a non-circular cross-section other than cylindrical, and one or more exhaust ducts 216 may be defined as having non-circular cylindrical duct sidewalls. For example, one or more of the exhaust duct structure 612, the outlet duct 614, or the collector duct 616 may have a polygonal prism shape having a polygonal cross section. Such a polygon may be any polygon, including, for example, a nonagon, a decagon, etc.

[0156] Figures 7A and 7B are perspective views of a MIRSS module 300 according to some exemplary embodiments. Figure 7C is a cross-sectional elevation view of the MIRSS module of Figure 7A along cross-sectional line VIIC-VIIC' of Figure 7B according to some exemplary embodiments.

[0157] Figure 8A is a perspective view of a MIRSS assembly 200 according to some exemplary embodiments. Figure 8B is a cross-sectional perspective view of the MIRSS assembly of Figure 8A along cross-sectional line VIIIB-VIIIB' of Figure 8A according to some exemplary embodiments.

[0158] Figure 9A is a perspective view of a nuclear reactor building including the MIRSS assembly of Figure 8A, according to some illustrative embodiments. Figure 9B is a cross-sectional elevation view of the nuclear reactor building of Figure 9A along cross-sectional line IXB-IXB' in Figures 9A and 9D, according to some illustrative embodiments. Figure 9C is a cross-sectional elevation view of the nuclear reactor building of Figure 9A along cross-sectional line IXC-IXC' in Figures 9A and 9D, according to some illustrative embodiments. Figure 9D is a cross-sectional top view of the nuclear reactor building of Figure 9A along cross-sectional line IXD-IXD' in Figure 9C, according to some illustrative embodiments. Figure 9E is a cross-sectional top view of the nuclear reactor building of Figure 9A along cross-sectional line IXE-IXE' in Figure 9C, according to some illustrative embodiments.

[0159] Figure 10A is a perspective view of a nuclear reactor building including the MIRSS assembly of Figure 8A, according to some illustrative embodiments. Figure 10B is a cross-sectional elevation view of the nuclear reactor building of Figure 10A along cross-sectional line XB-XB' in Figure 10A, according to some illustrative embodiments. Figure 10C is a cross-sectional top view of the nuclear reactor building of Figure 10A along cross-sectional line XC-XC' in Figure 10B, according to some illustrative embodiments. Figure 10D is a cross-sectional top view of the nuclear reactor building of Figure 10A along cross-sectional line XD-XD' in Figure 10B, according to some illustrative embodiments.

[0160] 7A-7C , in some exemplary embodiments, the MIRSS module 300 may be a MIRSS module 300-4 that may include a structural member (e.g., a beam, a plate, etc.), for example, at least a portion of the upper structural member 312 of the MIRSS module 300-4, thereby defining an exhaust duct structure 712 extending through the MIRSS module 300 to at least partially define between opposing inlet and outlet openings 216-O1 and 216-O2, thereby defining at least one exhaust duct 216 within the MIRSS module 300 (e.g., defining at least one or more duct sidewalls of the exhaust duct 216). As a result, the MIRSS module 300 may be configured to include an exhaust duct 216 without any additional exhaust manifold structure 610 being coupled to the MIRSS module 300. Unlike some exemplary embodiments of the MIRSS assembly 200, such as the exemplary embodiments shown in Figures 1A-2G, which may include the MIRSS module 300 and the exhaust manifold structure 610 as separately fabricated structures that are coupled together to at least partially define the annular structure 230 and the exhaust duct 216 (e.g., to define at least one or more duct sidewalls of the exhaust duct 216), in some exemplary embodiments, the MIRSS module 300 may include a structural member 302 that defines the exhaust duct structure 712 as part of the integral structure of one or more fabricated MIRSS modules 300, where the exhaust duct structure 712 defines at least one or more duct sidewalls of each separate exhaust duct 216 in one or more MIRSS modules 300. As a result, in some exemplary embodiments, a MIRSS module 300 such as that shown in Figures 7A-7C may be configured to define one or more exhaust ducts 216 without being coupled to a separately fabricated exhaust manifold structure 610, such that inserting the exhaust duct structure 612 of the exhaust manifold structure 610 into the module interior 308 of the MIRSS module 300 may enable the formation (e.g., construction) of a MIRSS assembly 200 that does not include any separately fabricated exhaust manifold structure 610 coupled to the MIRSS module 300.

[0161] While Figures 7A-7C show a MIRSS module 300 having a structural member 302 defining an exhaust duct 216 having one or more duct sidewalls defined by an exhaust duct structure 712 extending between openings 216-O1 and 216-O2 within the MIRSS module 300, and Figures 3A-5D show a MIRSS module 300 having a structural member 302 defining openings 216-O1 and 216-O2, and configured to define an exhaust duct 216 based on a separate exhaust manifold structure 610 being connected to the MIRSS module 300 such that an exhaust duct structure 612 extends through opening 216-O2 and extends to at least inlet opening 216-O1 to define one or more duct sidewalls of the exhaust duct 216, it will be understood that exemplary embodiments of the exhaust duct 216 within the MIRSS module 300 and / or MIRSS assembly 200 are not limited thereto. For example, in some exemplary embodiments, the MIRSS module 300, such as those shown in Figures 3A-3F and 4A-4D, may include a structural member 302, such as upper structural member 312, that defines at least the bottom and side walls of an upper shielded chamber 316 within the upper modular structure 310 and further defines openings 216-O1 and 216-O2 on either side of the upper shielded chamber 316, and an upper shielding material 318 that may be inserted into the shielded chamber may include a preformed structure (e.g., a preformed high-density concrete structure) having an outer shape corresponding to the shape of the upper shielded chamber 316 and further includes one or more inner surfaces that define a cylindrical conduit extending through the interior of the preformed structure between the openings on either side. The preformed structure may be inserted into the upper shielded chamber 316 so that the openings on either side of the preformed structure are aligned with each separate opening 216-O1 or 216-O2 (e.g., overlapping) such that the cylindrical space extending through the interior of the preformed structure between openings 216-O1 and 216-O2 completes the definition of the duct sidewall of the exhaust duct 216 extending between openings 216-O1 and 216-O2 within the MIRSS module 300.As a result, in some exemplary embodiments, exhaust duct 216 may be at least partially defined by upper shielding 318 (e.g., defined by duct sidewalls) in upper shielded chamber 316, instead of having duct sidewalls defined by structural members 302 or the duct structure of a separate, connected exhaust manifold structure. The pre-formed structure can be inserted into upper shielded chamber 316 prior to completing the containment top wall of shielded chamber 316 by connecting structural members 302 to upper modular structure 310. The pre-formed structure can be inserted into upper shielded chamber 316 either before or after MIRSS modules 300 are connected together to at least partially construct MIRSS assembly 200; for example, after MIRSS assembly 200 has been constructed and mounted on isolators 150. It will also be appreciated that the duct sidewalls of exhaust duct 216 may be defined by a combination of structural members 302 of the MIRSS module and one or more surfaces of shielding material 318 within upper shielded chamber 316.

[0162] In some exemplary embodiments, the MIRSS module 300 includes one or more exhaust duct structures 712 that define one or more exhaust ducts 216 extending through the MIRSS module 300 between its opposing outer surfaces, in which case the MIRSS module 300-4 may include multiple azimuthally offset portions 700-1 and 700-2 that are separate azimuth segments 300-A of the MIRSS module 300-4, and where an exhaust duct structure 712 may be present in more than one of the azimuth sections 700-1, 700-2 of a single MIRSS module 300-4, it may be present in one azimuth section 700-1 and not in one or more other azimuth sections 700-2 of the single MIRSS module 300, or may not be present in all azimuth sections of the MIRSS module 300.

[0163] 7A-7C, MIRSS module 300 may be MIRSS module 300-4, which may include multiple azimuthal sections 700-1, 700-2 defined by identical, azimuthally offset arrangements of structural member 302, excluding upper structural member 312, which includes a plate defining a portion of upper inner sidewall surface 354-U and opposing convex outer MIRSS module surface 310-S. As shown, azimuthal section 700-1 does not include any exhaust duct structure 712 extending between opposing surfaces 354-U and 310-S, and therefore the plate defining such surface omits openings 216-O1 or 216-O2 in azimuthal section 700-1. As further shown, azimuth section 700-2 has the same structural arrangement, defining the same or similar internal structure of the internal upper and lower shielded chambers 316 and 326, except that azimuth section 700-2 has an exhaust duct structure 712, and the upper structural member 312 defining surfaces 354-U and 310-S defines respective openings 216-O1 and 216-O2 in the second azimuth section, such that the exhaust duct structure 712 at least partially defines an exhaust duct 216 extending between openings 216-O1 and 216-O2 in azimuth section 700-2.

[0164] 7A-7C , the structure of the MIRSS module 300-4 may allow for easy fabrication of different MIRSS modules 300 with different arrangements of the exhaust ducts 216, without the need for a separate exhaust manifold structure 610 to be coupled to (e.g., inserted into) the MIRSS module 300. Such different arrangements may allow for fabrication of otherwise similarly structured MIRSS modules 300 that can be coupled together to form MIRSS assemblies 200 defining particular arrangements of one or more exhaust ducts 216 to define various flow paths for the high-temperature working fluid 244 exiting the collector cylinder 210, as described herein. As a result, the structure of the MIRSS module 300-4 may allow for rapid fabrication of multiple MIRSS modules 300-4 that can be coupled together to form MIRSS assemblies 200 defining particular arrangements of one or more flow paths for the high-temperature working fluid 244 exiting the collector cylinder 210.

[0165] 7A-7C, and further shown in Figures 8A-10D, exhaust duct structure 712 may have a square cross-section, and exhaust duct structure 712 may be considered a square duct, thus defining exhaust duct 216 as having square duct sidewalls. However, example embodiments are not limited thereto, and in some example embodiments, exhaust duct structure 712 may have a circular cross-section, a polygonal cross-section different from a square (e.g., any polygon including a nonagon, decagon, etc.), any non-circular cross-section, etc.

[0166] 8A and 8B, in some exemplary embodiments, the MIRSS assembly 200 may include multiple MIRSS modules 300 coupled together to define an annular structure 230, where the coupled MIRSS modules 300 are identical to the MIRSS module 300-4 shown in FIGS. 7A-7C except that the various coupled MIRSS modules 300 include different arrangements and / or inclusions of one or more exhaust duct structures 712 to define (e.g., define) a particular azimuthal (e.g., circumferential) arrangement of exhaust ducts 216 extending at least partially radially through the MIRSS assembly 200, which define a particular arrangement of the flow path of the high-temperature working fluid 244 exiting the collector cylinder 210.

[0167] For example, as shown in at least FIG. 8A, MIRSS assembly 200 may include at least MIRSS modules 300-41 and 300-42 coupled together to define an annular structure 230, where MIRSS modules 300-41 and 300-42 define exhaust ducts 216 extending through an azimuthal section of MIRSS module 300-41 and other azimuthal sections that do not include any such exhaust ducts 216. While MIRSS module 300-41 includes exhaust duct 216 in any of its azimuthal sections, MIRSS module 300-42 does not include any exhaust duct structure 712 therein, and the structural members 302 defining opposing faces 354-U and 310-S of MIRSS module 300-42 do not define openings 216-O1 or 216-O2 in MIRSS module 300-42. These different MIRSS modules 300-41 and 300-42 can be rapidly fabricated at a common site (e.g., the same remote location) using common materials and tooling because the structures of the azimuthal portions of MIRSS module 300-41 are relatively similar, except for exhaust duct structure 712 and openings 216-O1 and 216-O2 defined in surfaces 354-U and 310-S of MIRSS module 300-4. As a result, MIRSS modules 300-4 can be easily and efficiently fabricated and joined together to construct MIRSS assembly 200 that omits a separate exhaust manifold structure.

[0168] 8A and 8B , in some exemplary embodiments, flexible duct 620 may be coupled (e.g., directly coupled) to outlet opening 216-O2 of MIRSS assembly 200 and / or its MIRSS module 300-4 to establish an interface between vibration-isolated exhaust section 232 of reactor cooling system 130, which is defined at least in part by exhaust duct 216 including exhaust duct structure 712, and non-vibration-isolated exhaust section 120 of reactor cooling system 130. As a result, MIRSS assembly 200 may be more radially compact and may be placed within a smaller diameter reactor building 102.

[0169] 9A to 9E and 10A to 10D, the MIRSS assembly 200 shown in the figures may be the MIRSS assembly 200 shown in FIGS. 8A and 8B. As shown in Figures 9A-9E and 10A-10D, a MIRSS assembly 200 including an exhaust duct 216 having an exhaust duct structure 712 connected (e.g., directly connected) to each flexible duct 620 and each outlet opening 216-O2 thereof can be positioned within a reactor building 102 including openings 102-2O open to each separate flexible duct 620, thereby connecting the flexible duct 620 at each opening 620-O thereof to each opening 126-O1 of each non-vibration-isolated exhaust conduit 126, thereby establishing fluid communication between the vibration-isolated exhaust duct 216 of the MIRSS assembly 200 and one or more non-vibration-isolated exhaust systems 122 (e.g., one or more chimneys) that are open to the ambient environment and are thus configured to direct the high-temperature working fluid 244 received from the exhaust duct 216 via the flexible duct 620 to flow into the ambient environment 123.

[0170] 9A-10D, and further shown in FIGS. 1A-2G and 6A-6C, the flexible duct 620 may include bellows, flexible seals, expandable seals, etc. configured to bend (e.g., resiliently bend) in response to movement of the coupled exhaust duct 216 (e.g., exhaust duct structure 712) of the MIRSS assembly 200 relative to the non-isolated exhaust duct 126, without including a seal on the flow path extending through the flexible duct 620 between the exhaust duct 216 (e.g., exhaust duct structure 712) and the non-isolated exhaust duct 126, thereby maintaining the integrity of the reactor coolant system circuit 236 and the integrity of the reactor coolant system 130 of the nuclear power plant 100 during movement of the isolation assembly 190 with the isolated exhaust section 232, independent of the reactor building 102 and the non-isolated exhaust section 120.

[0171] 9A-9E, in some exemplary embodiments, a MIRSS assembly 200 including coupled MIRSS modules 300, such as the MIRSS modules 300-4 shown in FIGS. 7A-7C, 8A, and 8B, is configured to be mounted on a seismic isolator 150 in the reactor building 102 that defines one or more non-seismically isolated intake conduits 116 extending directly into (e.g., the intake openings 116-O open directly into) the downcomer annular gap 214 defined at least partially between the MIRSS assembly 200 and the lower building structure 102-1 (e.g., between the bulkhead 222 and the inner containment pit surface 102-11S), thereby enabling the nuclear power plant 100 to flow a working fluid 240 through a reactor coolant system 130 that is at least partially isolated from the seismic isolator 150. For example, as shown in Figures 9A-9E, one or more of the non-vibration-isolated inlet conduits 116 may extend to a respective separate inlet opening 116-O that opens directly into the downcomer annular gap 214 at a location within the downcomer annular gap 214 between (e.g., vertically between) the bottom opening 214-B of the downcomer annular gap 214 and the vibration isolator 150, thereby allowing the cold working fluid 242 to flow downward from the inlet opening 116-O toward the bottom opening 214-B of the downcomer annular gap 214 without flowing through a heat transfer path (e.g., a convective heat transfer path, an electrically conductive heat transfer path, a radiative heat transfer path, or any combination thereof) through the vibration isolator 150. In other words, the vibration isolator 150 may be located "upstream" of the inlet opening 116-O and thus may be external to the inlet flow path of the cold working fluid 242 and external to the circulation path 236 through which the working fluid 240 circulates through the reactor coolant system 130. The vibration isolator 150 may be exposed to the downcomer annular gap 214 or may be physically isolated from the downcomer annular gap 214 (e.g., by annular gap barriers and / or sealing structures).As a result, the MIRSS assembly 200 and / or the reactor building 102 (e.g., thermally isolated from at least the cold working fluid directed into the downcomer annulus) may be configured to at least thermally isolate (e.g., insulate) the isolator 150 from the working fluid 240 (e.g., cold working fluid 242) circulating in the circuit 236 of the reactor coolant system 130, thereby reducing, minimizing, or preventing heat transfer from the isolator 150 to the cold working fluid 242. Such an arrangement may be configured, for example, to mitigate (e.g., reduce, minimize, or prevent) excessive cooling of the isolator 150 by the working fluid 240 (e.g., cold working fluid 242) in a nuclear power plant 100 located in a relatively cold environment where the cold working fluid 242 may be relatively cold.

[0172] 10A-10D , in some exemplary embodiments, a MIRSS assembly 200 including coupled MIRSS modules 300, such as MIRSS module 300-4 shown in FIGS. 7A-7C, 8A, and 8B, may be configured to be mounted on seismic isolators 150 within the reactor building 102 such that the MIRSS assembly 200, together with one or more structures of the lower building structure 102-1, at least partially defines an inlet flow channel, e.g., including the inlet conduit 118, in fluid communication between the non-isolated inlet conduit 116 and the downcomer annular gap 214. The MIRSS assembly 200 may thus be configured to allow cold working fluid 242 to flow in a heat transfer path that passes through one or more of the isolators 150, thereby enabling cooling of the one or more isolators and mitigating potential damage to the isolators 150 due to thermal loads. The nuclear power plant 100 may further provide "localized heating" of one or more of the seismic isolators 150 to mitigate or minimize potential overcooling of the seismic isolators 150 by the cold working fluid 242, for example, in exemplary embodiments where the nuclear power plant 100 is exposed to relatively cold environmental conditions where the cold working fluid 242 is relatively cold (e.g., below 0°F) for extended periods of time. In some exemplary embodiments, one or more heaters 154 may be coupled to one or more of the seismic isolators 150 and configured to directly heat the one or more of the seismic isolators 150 via electrical conduction. For example, the one or more heaters 154 may include one or more electrical resistance heaters. In some exemplary embodiments, the one or more heaters 154 may be configured to provide localized heating of the seismic isolators 150 via radiative, conductive, or convective heating. For example, one or more heaters 154 may be directly connected to one or more vibration isolators 150 and configured to heat the cold working fluid 242 before the cold working fluid 242 flows through a heat transfer path that passes through the one or more vibration isolators 150.For example, the one or more heaters 154 may be disposed between the one or more isolators 150 and the openings 116-O of the one or more non-isolated inlet conduits 116, and thus may be "upstream" of the one or more isolators 150 with respect to the flow of the working fluid 242, and may be configured to "preheat" the cold working fluid 242 prior to it passing through the one or more isolators 150. In some exemplary embodiments, the one or more heaters 154 may include one or more space heaters, for example, one or more electrical resistance heaters configured to heat the cold working fluid 242 traveling across and / or through the one or more heaters 154 "upstream" of the one or more isolators 150.

[0173] 11 is a flowchart illustrating a method for constructing a nuclear power plant, according to some example embodiments. The method illustrated in FIG. 11 may be implemented with reference to any of the example embodiments of MIRSS assembly 200, MIRSS module 300, reactor building 102, nuclear power plant 100, or combinations thereof described herein, including any of the example embodiments illustrated in FIGS. 1A-10D.

[0174] In S1102, the method includes constructing at least a lower building structure 102-1 of the reactor building 102 at a reactor building construction site in the nuclear power plant 100, the lower building structure 102-1 being configured to structurally support and contain a reactor containment system 140 including a nuclear reactor 142. The lower building structure 102-1 constructed in S1102 may include at least one structural support surface 102-12 configured to support a structural load of the reactor containment system 140 on a foundation 170. In some exemplary embodiments, the construction in S1102 includes constructing the foundation 170 and further constructing the lower building structure 102-1 on the foundation 170. In some exemplary embodiments, the lower building structure 102-1 includes the foundation 170 as an integral element of the lower building structure 102-1, such that construction of the lower building structure 102-1 includes construction of the foundation 170.

[0175] 1A-1H, the lower building structure 102-1 includes a containment pit 102-11, also referred to as a containment pit, configured to at least partially contain a reactor containment system 140 of the nuclear power plant 100 within the reactor building 102. Accordingly, in some exemplary embodiments, the method in S1102 may include constructing the containment pit 102-11. The lower building structure 102-1 may include one or more structural support surfaces 102-12 configured to support the structural loads (e.g., weight) of the isolation assemblies 190, including the reactor containment system 140, that will be included in the reactor building 102 under construction. Accordingly, the method in S1102 may include forming the one or more structural support surfaces 102-12, e.g., forming the one or more structural support surfaces 102-12 to at least partially enclose the containment pit 102-11. In some exemplary embodiments, the lower reactor structure 102-1 may include a concrete structure, a reinforced (e.g., steel reinforced) concrete structure, etc. Thus, constructing the lower building structure 102-1 in S1102 may include pouring concrete into a mold that may or may not include metal (e.g., steel) reinforcement structure therein to form one or more portions of the lower building structure 102-1.

[0176] At S1104, the method may include mounting (e.g., coupling) a plurality of isolators 150 onto at least one support surface 102-12. The plurality of isolators 150 may be mounted onto the at least one structural support surface 102-12 based on embedding one or more steel structures of the isolators 150 within the concrete structure of the underlying building structure 102-1. Thus, in some exemplary embodiments, mounting at S1104 may be performed simultaneously with and / or as part of constructing the underlying building structure at S1102. The isolators 150 may include any known isolators that may be configured to allow two- or three-dimensional translational and / or rotational movement of the structure supported by the isolators 150, independent of the underlying building structure 102-1. A vibration isolator 150 configured to allow translational and / or rotational movement in three dimensions (e.g., horizontally and / or vertically) of a structure supported by the vibration isolator 150 may also be referred to herein as a three-dimensional isolator, a 3D isolator, etc. Vibration isolator 150, including, for example, a 3D isolator, may also include one or more springs, laminated rubber bearings, etc., which are configured to be flexible and allow flexible structural support of a supporting structure such that the supported structure is at least partially vibrationally isolated from the structure on which the vibration isolator 150 rests (e.g., mounted).

[0177] In S1112, the method may include manufacturing (also referred to herein as fabricating) one or more MIRSS modules 300 according to any of the exemplary embodiments. One or more MIRSS modules 300 may be fabricated in S1112 at a remote location (e.g., separate, remote from) the reactor building construction site where the reactor building 102 is being constructed (e.g., outside the boundaries of the nuclear power plant 100 where the reactor building construction site is located). For example, separate MIRSS modules 300 may be fabricated at multiple separate remote locations that may be located in different towns, geographic regions, etc. relative to the nuclear power plant site and, in turn, the reactor building construction site. Each MIRSS module 300 may be constructed using a variety of fabrication processes using a variety of raw materials, including steel plate girders, plate steel, steel beams, I-beams, etc., to fabricate one or more MIRSS modules 300 according to any of the exemplary embodiments. In some exemplary embodiments, various MIRSS modules 300, including any of MIRSS modules 300-1, 300-2, 300-3, and / or 300-4, may be fabricated independently using one or more fabrication fixtures using metal structural members including, for example, steel beams, including structural members 302 of MIRSS assembly 200 that at least partially include MIRSS modules 300 and, in turn, such MIRSS modules 300 coupled together. At S1114, MIRSS modules 300 may be transported, collectively or independently, from the fabrication location to the reactor building construction site (e.g., on one or more flatbed trucks).

[0178] In some exemplary embodiments, one or more MIRSS modules 300 may be fabricated "on-site" (e.g., within the boundaries of the nuclear power plant where the reactor building construction site is located), thereby reducing or eliminating transportation of S1114.

[0179] In S1132, the reactor containment system 140 is structurally supported on the cylindrical reactor support structure 202, such that the MIRSS assembly 200 is configured to define a seismic isolation assembly within the nuclear power plant 100 that includes the reactor containment system 140 and is seismically isolated from the reactor building 102, and a collector cylinder 210 configured to at least partially receive the reactor containment system 140 (e.g., receive at least the protective vessel 144 of the reactor containment system 140), whereby the MIRSS assembly 200 is constructed at least in S1134 by coupling the MIRSS modules 300 together to collectively define a cylindrical reactor support structure 202 configured to structurally support the reactor containment system 140 on a plurality of seismic isolators 150, thereby forming a reactor containment system. The collector cylinder 210 is configured to at least partially define an uprising annular gap 224 between the inner cylindrical surface 212 of the collector cylinder 210 and the outer sidewall surface 140-S of the reactor containment system 140 (e.g., the outer sidewall 144-S of the protective vessel 144, or in an exemplary embodiment in which the reactor containment system 140 does not include any protective vessel, the outer sidewall surface of the primary vessel 146, etc.), and a partition 222 that at least partially defines a downcomer annular reduction group 214 between the outer cylindrical surface of the partition 222 and the reactor building 102, and to at least partially define a plurality of exhaust ducts 216 extending from the collector cylinder 210 through the interior 204 of the cylindrical reactor support structure 202 (e.g., to the outer sidewall surface 200-S of the MIRSS assembly 200 opposite the inner cylindrical surface 212 of the collector cylinder 210).

[0180] In an exemplary embodiment in which the MIRSS assembly 200 under construction in S1132 includes one or more exhaust manifold structures 610 (also referred to herein as exhaust manifolds), the method may include, in S1122, manufacturing (e.g., fabricating) such exhaust manifold structures 610 at one or more remote locations. Such exhaust manifold structures 610 may be fabricated at the same remote location where one or more MIRSS modules 300 are fabricated in S1112, or may be fabricated at one or more remote locations different from the one or more remote locations where one or more MIRSS modules 300 are fabricated in S1112. The method may further include, in S1124, transporting the one or more exhaust manifold structures (e.g., on one or more flatbed trucks) to the construction site of the reactor building.

[0181] The method may further include, in S1132 and S1136, constructing a MIRSS assembly 200 based on connecting one or more exhaust manifold structures 610 to one or more MIRSS modules 300 and / or an annular structure 230 defined at least in part by the MIRSS modules 300 connected together in S1134, so that the constructed MIRSS assembly 200 includes one or more exhaust manifold structures 610 according to some exemplary embodiments. Performing such connection in S1136 may further include inserting one or more exhaust duct structures 612 of the exhaust manifold structure 610 into and at least partially through the cylindrical reactor support structure 202 (e.g., interior 204), which may include inserting at least one exhaust duct structure 612 through the internal space of one or more upper module structures 310 of one or more MIRSS modules 300 of the MIRSS assembly 200 so that the inlet opening 610-O1 defined by the at least one exhaust duct structure 612 is fluidly connected to (e.g., opens directly toward) the top 210-U of the collector cylinder 210, and so that the at least one exhaust duct structure 612 at least partially defines at least one exhaust duct 216 (e.g., defines at least a duct side wall of the at least one exhaust duct 216). As a result of such connection in S1136, at least one exhaust duct structure 612 of the exhaust manifold structure 610 may at least partially define one or more exhaust ducts 216 so as to be configured to be fluidly connected with the top 224-U of the riser annular gap 224 defined at least in part by the top 210-U of the collector cylinder 210 of the MIRSS assembly 200 (e.g., so that the inlet duct opening 610-O1 of the exhaust manifold structure 610 defined by the at least one exhaust duct structure 612 extends toward and / or through the first opening 216-O1 defined by one or more MIRSS modules 300).

[0182] In some exemplary embodiments, coupling one or more exhaust manifold structures 610 to one or more MIRSS modules 300 in S1136 may be performed after coupling the MIRSS modules 300 together to establish the annular structure 230 in S1134, although exemplary embodiments are not limited in this respect. For example, in some exemplary embodiments, one or more exhaust manifold structures 610 may be coupled to one or more MIRSS modules 300 prior to the MIRSS modules 300 being coupled together in S1134. In some exemplary embodiments, coupling in S1136 may be performed later, for example, after the MIRSS assembly 200 is mounted (e.g., installed) at the reactor building construction site, as described below.

[0183] In some exemplary embodiments, performing construction in S1132 may further include connecting an HAA seal 294 to the outer sidewall surface 200-S of the MIRSS assembly 200, connecting one or more flexible ducts 620 to each separate outlet opening 610-O2 and / or 216-O2 of the MIRSS assembly 200, and connecting a well seal 298 to the inner cylindrical surface 212 of the cylindrical reactor support structure 202 of the MIRSS assembly 200, etc.

[0184] In some exemplary embodiments, for example, as shown in Figures 7A to 10D, the MIRSS module 300 may include an exhaust duct structure 712 extending between opposing openings 216O1 and 216-O2 of the MIRSS module 300 to at least partially define one or more exhaust ducts 216 of the MIRSS assembly 200, and the exhaust hold structure 610 may be omitted from the MIRSS assembly 200, and operations S1122, S1124, and S1136 may be omitted.

[0185] At S1142, the method includes mounting the MIRSS assembly 200 on the seismic isolator 150 such that the MIRSS assembly 200 is structurally supported on the isolator 150 (e.g., such that the isolator 150 supports the structural load of the MIRSS assembly 200 on the underlying building structure 102-1 and further transfers the structural load of the MIRSS assembly 200 to the underlying building structure 102-1). Such mounting may include lifting (e.g., hoisting) the MIRSS assembly 200 as a single-piece structure via a crane and lowering it onto the isolator 150 (e.g., in a single lifting motion). As a result of the MIRSS assembly 200 being mounted on the isolator 150, the MIRSS assembly 200 may define a seismic isolation assembly 190 in the nuclear power plant 100 that is seismically isolated from the reactor building 102. In some exemplary embodiments, the seismic isolation assembly 190 may include the MIRSS assembly 200 and the reactor containment system 140. In some exemplary embodiments, isolation assembly 190 may be limited to MIRSS assembly 200 and reactor containment system 140 to reduce the structural load of isolation assembly 190 on isolator 150 .

[0186] In some exemplary embodiments, loading the MIRSS assembly 200 onto the seismic isolators 150 in S1142 includes lowering the MIRSS assembly 200 into at least the containment pit 102-11 of the lower building structure 102-1 such that the MIRSS assembly 200 is structurally supported on a plurality of seismic isolators 150 that extend in a circumferential pattern around the containment pit 102-11 and that extend downwardly at least partially into the containment pit 102-11 through a top opening 102-11O of the containment pit 102-11. The cylindrical reactor support structure 202 may be mounted directly on the seismic isolators 150 to structurally support the MIRSS assembly 200 and the remainder of the reactor containment system 140 on the seismic isolators 150. The MIRSS assembly 200 may, in turn, structurally support the reactor containment system 140 within the collector cylinder 210 such that the MIRSS assembly 200 extends downwardly at least partially into the containment pit 102-11.

[0187] In S1152, the method includes mounting at least a portion of reactor containment system 140 on MIRSS assembly 200 such that MIRSS assembly 200 (e.g., its cylindrical reactor support structure 202) structurally supports at least a portion of reactor containment system 140 on a plurality of seismic isolators 150, and thus seismic isolation assembly 190 includes reactor containment system 140. In some exemplary embodiments, reactor containment system 140 includes reactor 142 within (e.g., containment section of) reactor containment system 140 defined by protective vessel 144, primary vessel 146, and head 148 being mounted onto MIRSS assembly at S1152 simultaneously with reactor containment system 140, although exemplary embodiments are not limited in this respect. In some exemplary embodiments, a portion of the reactor containment system 140 (e.g., the protective vessel 144) may be mounted on the MIRSS 200 prior to the MIRSS assembly 200 being mounted on the seismic isolation device 150 in S1142, and after the MIRSS assembly 200 is mounted on the seismic isolation device 150 in S1142, the remaining portions of the reactor containment system 140 (e.g., the primary vessel 146, the reactor 142, etc.) may be coupled to the mounted portion of the reactor containment system 140 in S1152 to complete construction of the reactor containment system 140. It will be appreciated that mounting the reactor containment system 140 on the MIRSS assembly 200 results in the reactor containment system 140 transferring some or all of the structural loads (e.g., weight) of the reactor containment system 140 to the MIRSS assembly 200, thereby causing the MIRSS assembly 200 (e.g., cylindrical reactor support structure 202) to structurally support the reactor containment system 140 (e.g., structurally support the reactor containment system 140 to the foundation 170 via the seismic isolation device 150 mounted on the lower building structure 102-1).In some exemplary embodiments, loading in S1152 may include lifting reactor containment system 140 with a crane (e.g., hoisting the entire reactor containment system 140 as a single unit) and lowering reactor containment system 140 into collector cylinder 210 defined by annular structure 230 of MIRSS assembly 200 until structural elements of reactor containment system 140 contact and are structurally supported by cylindrical reactor support structure 202 of MIRSS assembly 200. In some exemplary embodiments, loading in S1152 is performed prior to loading MIRSS assembly 200 onto seismic isolator 150, such that loading in S1142 loads the combination of MIRSS assembly 200 and reactor containment system 140 structurally supported thereon onto seismic isolator 150.

[0188] At S1162, the method includes coupling the MIRSS assembly 200 to the non-vibration-isolated exhaust section 120 of the reactor cooling system 130. Such coupling may include coupling an opening 126-O1 of a non-vibration-isolated exhaust conduit 126 of the non-vibration-isolated exhaust section 120 of the reactor cooling system 130 configured to direct the high-temperature working fluid 244 to the surrounding environment 123 to one or more exhaust ducts 216 of the MIRSS assembly 200 (e.g., opening 216-O2 defined by one or more exhaust duct structures 712 extending through and / or at least partially defining the one or more exhaust ducts 216, opening 610-O2 of an exhaust manifold structure 610 coupled to the annular structure 230, etc.).

[0189] In some exemplary embodiments, the MIRSS assembly 200 includes one or more exhaust manifold structures 610, and the connection in S1162 may include connecting an exhaust duct 614 (e.g., outlet opening 610-O2) of the one or more exhaust manifold structures 610 to a non-vibration-isolated exhaust conduit 126 that is part of the non-vibration-isolated exhaust section 120 for the reactor cooling system 130 and is in fluid communication with the exhaust system 122 (e.g., a chimney open to the surrounding environment 123) of the nuclear power plant 100. In some exemplary embodiments, such connection in S1162 may include connecting the flexible duct 620 to the outlet duct 614 (e.g., outlet opening 610-O2) and further connecting the flexible duct 620 to the non-vibration-isolated exhaust conduit 126 (e.g., to opening 126-O1 of the non-vibration-isolated exhaust conduit 126) (e.g., connecting to opening 620-O2 of the flexible duct 620) so that the flexible duct 620 is connected between the opening 610-O2 defined by the outlet duct 614 of the exhaust manifold structure 610 and the opening 126-O1 of the non-vibration-isolated exhaust conduit 126 of the non-vibration-isolated exhaust section 120, thereby establishing fluid communication between the vibration-isolated exhaust section 232 and the non-vibration-isolated exhaust section 120 of the reactor cooling system 130. In some exemplary embodiments, flexible duct 620 is coupled to opening 610-O2 of outlet duct 614 in S1122 as part of the construction of exhaust manifold structure 610. In some exemplary embodiments, if exhaust manifold structure 610 is part of exhaust manifold assembly 600 fabricated in S1122 and further includes non-vibration-isolated exhaust conduit 126 already coupled to outlet duct 614 via flexible duct 620 in S1122, coupling in S1162 may include, for example, coupling non-vibration-isolated exhaust conduit 126 to a portion of non-vibration-isolated exhaust section 120 of reactor cooling system 130, including exhaust system 122, to establish fluid communication from exhaust manifold structure 610 to exhaust system 122 and the open ambient environment 123 of exhaust system 122.

[0190] In some exemplary embodiments, if the MIRSS assembly 200 omits the exhaust manifold structure 610 (e.g., if the method omits S1122, S1124, and S1136), the coupling in S1162 may include coupling a flexible duct 620 to the outlet opening 216-O2 of at least one exhaust duct 216 of the MIRSS module 300 that includes the MIRSS assembly 200 (e.g., to the outlet opening 216-O2 of the exhaust duct 216 that is defined at least in part by the exhaust duct structure 712 shown in Figures 7A-7C), and further coupling the flexible duct 620 to the non-vibration-isolated exhaust conduit 126 to establish fluid communication between the exhaust duct 216 and the non-vibration-isolated exhaust conduit 126.

[0191] In S1172, the method may include, for example, constructing an upper building structure 102-2 on the lower building structure 102-1 such that the upper building structure 102-1 is structurally supported on the lower building structure 102-1 independently of the isolation assembly 190, and thus the isolation assembly 190 is vibrationally isolated from both the lower and upper building structures 102-1 and 102-2.

[0192] Constructing the upper building structure 102-2 on the lower building structure 102-1 may establish containment of the interior 108 of the reactor building 102 and at least partially define an HAA 292 between one or more interior surfaces of the upper building structure 102-2 and the floor structure 290 of the isolation assembly 190. As a result, constructing in S1172 may seismically isolate the isolation assembly 190 from the lower building structure 102-1 and the upper building structure 102-2. The MIRSS assembly 200 may include an HAA seal 294 between the floor structure 290 constructed in S1172 and the upper building structure 102-2 to seal (e.g., isolate) the HAA 292 from the air intake conduit 118 located at least partially axially below the floor structure 290 of the MIRSS assembly 200. In some exemplary embodiments, the MIRSS assembly 200 includes a well seal 2298 that is a seal between the cylindrical reactor support structure 202 and the reactor containment system 140 (e.g., between the cylindrical reactor support structure 202 and the protective vessel 144) to at least partially define the top 224-U of the riser annular gap 224, which may further seal (e.g., isolate) the HAA 292 from the riser annular gap 224 that is positioned at least partially axially below the floor structure 290 of the MIRSS assembly 200.

[0193] In S1182, the method may include supplying one or more shielding materials 390 into one or more shielded chambers 296 of the on-board MIRSS assembly 200 (e.g., one or more shielded chambers 390 of one or more MIRSS modules 300 of the MIRSS assembly 200) to configure the MIRSS assembly 200 to shield (e.g., provide radiation and / or thermal) structures, equipment, and / or passageways external to the MIRSS assembly 200, such as from the reactor containment system 140, the riser annular gap 224, etc. In some exemplary embodiments, the supplying in S1182 may be performed by injecting (e.g., by a boom crane) the one or more shielding materials 390 into the one or more shielded chambers 296 of the MIRSS assembly 200 after on-boarding in SS152. In some exemplary embodiments, different shielding materials 390 may be supplied into different shielded chambers 296 to configure the MIRSS assembly 200 to provide different types and / or degrees of shielding to different areas. For example, providing one or more shielding materials 390 in S1182 may include providing a first lower shielding material 328-1 including a thermally insulating (e.g., insulating) material within an inner lower shielding chamber 326-1 to provide a thermal expansion break between the riser annular gap 224 and the downcomer annular gap 214, and further providing an upper shielding material 318 including a high-density concrete radiation shielding material within an upper shielding chamber 316 of an upper module structure 310 of the MIRSS modules 300 that collectively define the cylindrical reactor support structure 202, thereby providing radiation shielding of the vibration isolation device 150 radially outward of the cylindrical reactor support structure 202. In some exemplary embodiments, the supplying in S1182 may be performed as part of the construction of the MIRSS assembly in S1132, prior to loading the MIRSS assembly 200 onto the seismic isolation device 150 (e.g., prior to lifting and lowering the MIRSS assembly 200 at least partially into the storage pit 102-110 and placing the MIRSS assembly 200 on the seismic isolation device 150).In some exemplary embodiments, the supplying in S1182 may be performed separately from each individual MIRSS module 300 as part of creating the MIRSS module in S1112, so that the MIRSS modules 300 transported in S1114 and connected together in S1134 may already include one or more shielding materials 390 within their one or more shielding chambers 392.

[0194] In S1192, the method may include configuring one or more heaters 154 (e.g., one or more electrical resistance heaters) to one or more of the seismic isolation devices 150 or to a portion of the reactor building 102 or MIRSS assembly 200, thereby providing "localized heating" of the one or more seismic isolation devices 150.

[0195] It will be understood that, although example embodiments are not limited to, fabricating in S1112 may include fabricating and manufacturing MIRSS module 300 based on fabricating at least one upper modular structure 310 and one or more axially stacked lower modular structures 320, and connecting such modular structures together to fabricate MIRSS module 300. For example, in some example embodiments, fabricating in S1112 may include fabricating (e.g., constructing) MIRSS module 300 as a single-piece structure instead of independently fabricating and connecting separate upper and / or lower modular structures 310 and / or 320.

[0196] 11 includes operations S1112, S1114, and S1134 of fabricating one or more MIRSS modules 300, transporting the one or more MIRSS modules to a reactor building construction site, and connecting the MIRSS modules together to establish (e.g., define) the annular structure of MIRSS assembly 200, but it will be understood that example embodiments are not limited in this regard. For example, in some example embodiments, MIRSS assembly 200 may be a non-modular isolated reactor support system (IRSS) that is at least partially constructed as a single-piece structure in S1132, instead of being constructed based on connecting MIRSS modules 300 together, and thus operations S1112, S1114, and S1134 may be omitted. In some exemplary embodiments, the MIRSS module 300 may be omitted entirely, and the MIRSS may be constructed as a single piece "on site" in the lower building structure 102-1 (e.g., at least partially within the containment pit 102-11) or adjacent to the construction site of the reactor building 102, and then mounted to the seismic isolator 150. As a result, in some exemplary embodiments, operations S1112, S1114, and S1134 may be omitted from the method shown in FIG.

[0197] In some exemplary embodiments, fabricating in S1112 may include fabricating separate upper and lower modular structures 310, 320 without connecting such modular structures together to form azimuthal segment 230-A of annular structure 230, and the independently fabricated upper and lower modular structures 310, 320 may be transported to the construction site of reactor building 102 individually or together (without being connected together) in S1114. In such exemplary embodiments, MIRSS assembly 200 may be constructed in S1132 based on axially stacking and connecting separate groups (e.g., rings) of lower modular structures 320 atop each other in S1134, and then connecting upper modular structures 310 (e.g., individually or as an constructed cylindrical reactor support structure 202) onto the connected set (e.g., ring) of lower modular structures 320 to at least construct annular structure 230 and at least partially construct MIRSS assembly 200. The MIRSS assembly 200 thus constructed may then be mounted on a vibration isolator at S1142.

[0198] In some exemplary embodiments, the MIRSS assembly 200 may be erected in S1142 on the lower building structure 102-1 (e.g., at least partially within the containment pit 102-11) based on either linking the MIRSS modules 300 together or erecting the MIRSS assembly 200 as a single construction structure. As a result, in some exemplary embodiments, the mounting in S1142 may be partially or wholly omitted from the method shown in FIG. 11 because the MIRSS assembly 200 may be erected “in place of” the seismic isolators 150 or above and adjacent to where the seismic isolators 150 will be mounted, such that the mounting in S1142 simply involves lowering (e.g., a hydraulic jack lowered to mount the MIRSS assembly 200 onto the isolators at S1142) the MIRSS assembly 200 erected in S1132 above and adjacent to where the isolators 150 will be mounted (either before or after the isolators 150 were mounted in S1104).

[0199] According to some exemplary embodiments, a nuclear power plant described in any of the exemplary embodiments may be operated to generate power (e.g., heat, electricity, etc.) from its nuclear reactor. Such a nuclear power plant may include nuclear power plant 100 as shown in FIGS. 1A-1H, but may also include a nuclear power plant described in any of the exemplary embodiments. Such a nuclear power plant may include a nuclear power plant constructed according to the method shown in FIG. 11. Such a nuclear power plant may include a nuclear power plant constructed according to any of the exemplary embodiments. Thus, methods according to some exemplary embodiments may include a method of operating a nuclear power plant described in any of the exemplary embodiments, where the method includes generating power (e.g., heat, electricity, etc.) using a nuclear reactor of a nuclear power plant described in any of the exemplary embodiments, a nuclear power plant constructed according to a method according to any of the exemplary embodiments, etc.

[0200] While numerous exemplary embodiments have been disclosed herein, it should be understood that other modifications are possible. Such modifications should not be considered a departure from the spirit and scope of the inventive concept, and all modifications that would become apparent to one skilled in the art are intended to be included within the scope of the following claims. In addition, although processes have been disclosed herein, it should be understood that the elements of the described processes may be implemented in different orders, using different element selections, combinations thereof, etc. For example, some exemplary embodiments of the disclosed processes may be implemented using fewer elements than those illustrated and described, and some exemplary embodiments of the disclosed processes may be implemented using more elements than those illustrated and described.

[0201] Exemplary embodiments: Example 1: A nuclear power plant, comprising: a reactor containment system including a nuclear reactor; a reactor building configured to structurally support a reactor containment system on a foundation and to house the reactor containment system within the reactor building; a plurality of seismic isolation devices coupled to the reactor building; a modular isolated reactor support system (MIRSS) assembly; MIRSS assembly the MIRSS assembly defines a seismic isolation assembly within a nuclear power plant including a reactor containment system, the cylindrical reactor support structure configured to structurally support the reactor containment system on a plurality of seismic isolators so as to be seismically isolated from the reactor building; a collector cylinder configured to at least partially receive the reactor containment system based on the reactor containment system being structurally supported by a cylindrical reactor support structure, the collector cylinder configured to at least partially define a riser annular gap between an inner cylindrical surface of the collector cylinder and an outer sidewall surface of the reactor containment system; a bulkhead configured to at least partially define a downcomer annular gap between an outer cylindrical surface of the bulkhead and the reactor building, a bottom opening of the downcomer annular gap being in fluid communication with a bottom opening of the riser annular gap; a plurality of exhaust ducts extending from the collector cylinder through the interior of the cylindrical reactor support structure.

[0202] Example 2: The MIRSS assembly pumps the working fluid through downwardly through the downcomer annular gap to a bottom opening of the downcomer annular gap; flowing from the bottom opening of the downcomer annular gap to the bottom opening of the upcomer annular gap; flowing the working fluid through the riser annulus to the top of the riser annulus in response to changes in air density due to the working fluid absorbing heat from both the reactor containment system and the collector cylinder; 10. The nuclear power plant of Example Embodiment 1 configured to exhaust from the isolation assembly by flowing through one or more exhaust ducts of the plurality of exhaust ducts from the top of the riser annular gap through an interior of the MIRSS assembly.

[0203] Example 3: The nuclear power plant of Example 2, wherein the MIRSS assembly is configured to couple one or more exhaust ducts to an opening in a non-vibration-isolated exhaust of a reactor coolant system configured to direct the working fluid to an ambient environment.

[0204] Example 4: The nuclear power plant as described in exemplary embodiment 3, wherein the MIRSS assembly includes a flexible duct coupled between the one or more exhaust ducts and an opening in a non-isolated exhaust portion of the reactor coolant system, the flexible duct configured to establish fluid communication between the isolated portion of the reactor coolant system and the non-isolated exhaust portion of the reactor coolant system.

[0205] Example 5: The nuclear power plant described in exemplary embodiment 4, wherein the MIRSS assembly comprises an exhaust manifold structure, the exhaust manifold structure at least partially defining one or more exhaust ducts and an outlet duct coupled to the one or more exhaust ducts, the outlet duct configured to be coupled between the one or more exhaust ducts and the flexible duct.

[0206] Example 6: The nuclear power plant as described in Exemplary Embodiment 5, wherein the exhaust manifold structure at least partially defines at least two exhaust ducts coupled in parallel with the outlet duct.

[0207] Example 7: The nuclear power plant of exemplary embodiment 2, wherein the MIRSS assembly comprises a plurality of MIRSS modules coupled together to collectively define a cylindrical reactor support structure, a collector cylinder, a bulkhead, and a plurality of exhaust ducts.

[0208] Example 8: The nuclear power plant as described in example embodiment 7, wherein each MIRSS module of the plurality of MIRSS modules defines a distinct azimuthal segment of the cylindrical reactor support structure, a distinct azimuthal segment of the collector cylinder, and a distinct azimuthal segment of the bulkhead.

[0209] Example 9: Multiple MIRSS modules a plurality of upper modular structures collectively defining a cylindrical reactor support structure; a plurality of lower modular structures axially stacked below the plurality of upper modular structures; a plurality of lower modular structures stacked to collectively define a bulkhead; 8. The nuclear power plant of Exemplary Embodiment 7, wherein the plurality of upper modular structures and the plurality of lower modular structures collectively define a collector cylinder.

[0210] Example 10: The nuclear power plant of Exemplary Embodiment 9, wherein at least one upper modular structure of the plurality of upper modular structures at least partially defines one or more exhaust ducts.

[0211] Example 11: The nuclear power plant of exemplary embodiment 1, wherein the MIRSS assembly is configured to define at least one shielded chamber within the MIRSS assembly and radially outward from the collector cylinder, the at least one shielded chamber configured to hold at least one shielding material.

[0212] Example 12: The nuclear power plant of exemplary embodiment 2, wherein the MIRSS assembly is configured to direct the working fluid to the downcomer annular gap via a heat transfer path that passes through at least one isolator of the plurality of isolators, thereby causing the working fluid to remove heat from the at least one isolator by the MIRSS assembly.

[0213] Example 13: The nuclear power plant of exemplary embodiment 12, further comprising a heater configured to heat the at least one isolator.

[0214] Example 14: The nuclear power plant of Exemplary Embodiment 2, wherein the plurality of vibration isolators are at least partially insulated from the working fluid directed into the downcomer annular gap.

[0215] Example 15: A seismic isolation assembly defines a floor structure of a head access area (HAA) housed above the floor structure by an upper building structure of a reactor building, such that the floor structure is seismically isolated relative to the upper building structure that houses the HAA above the floor structure; 10. The nuclear power plant as described in Exemplary Embodiment 1, wherein the MIRSS assembly further comprises an HAA seal configured to establish a seal between the floor structure and the upper building structure.

[0216] Example 16: A Modular Isolation Reactor Support System (MIRSS) module configured to define an azimuthal portion of an annular structure, comprising: an upper modular structure defining a distinct azimuthal segment of the annular cylindrical reactor support structure, the upper modular structure configured to structurally support at least a portion of the structural loads of a reactor containment system including the nuclear reactor; one or more lower modular structures axially stacked below the upper modular structure, the one or more lower modular structures collectively defining distinct azimuthal segments of a partition wall of the annular structure; A MIRSS module, wherein the upper modular structure and one or more lower modular structures have respective inner sidewall surfaces that collectively define distinct azimuthal segments of an annular collector cylinder.

[0217] Example 17: A MIRSS module as described in exemplary embodiment 16, wherein the upper modular structure is configured to at least partially define a shielded chamber within a module of the upper modular structure, and the upper modular structure is configured to hold shielding material within the shielded chamber.

[0218] Example 18: The MIRSS module of exemplary embodiment 16, wherein the upper module structure is configured to at least partially define one or more exhaust ducts extending from separate azimuthal segments of the collector cylinder through a module interior of the upper module structure.

[0219] Example 19: A MIRSS assembly, comprising a plurality of MIRSS modules, each MIRSS module of the plurality of MIRSS modules being the MIRSS module of exemplary embodiment 16, the plurality of MIRSS modules being azimuthally coupled to collectively define a ring-shaped structure, such that the MIRSS assembly: a cylindrical reactor support structure having an annular configuration, the cylindrical reactor support structure configured to structurally support a reactor containment system; a collector cylinder of annular configuration, the collector cylinder configured to at least partially receive a reactor containment system based on the reactor containment system being structurally supported by a cylindrical reactor support structure, the reactor containment system including a nuclear reactor, the collector cylinder configured to at least partially define a riser annular gap between an inner cylindrical surface of the collector cylinder and an outer sidewall surface of the reactor containment system; a bulkhead of annular construction, the bulkhead at least partially defining a downcomer annular gap between an outer cylindrical surface of the bulkhead and a reactor building configured to structurally support the reactor containment system on a foundation, the bulkhead configured to contain the reactor containment system within the reactor building, a bottom opening of the downcomer annular gap being in fluid communication with a bottom opening of the riser annular gap; The MIRSS assembly includes a plurality of exhaust ducts extending from the collector cylinder through the interior of the cylindrical reactor support structure.

[0220] Example 20: The MIRSS assembly of exemplary embodiment 19, wherein the MIRSS assembly is configured to discharge the working fluid from the MIRSS assembly by flowing the working fluid downward through the downcomer annular gap to a bottom opening of the downcomer annular gap, from the bottom opening of the downcomer annular gap to a bottom opening of the riser annular gap, through the riser annular gap to the top of the riser annular gap, and from the top of the riser annular gap through one or more exhaust ducts of a plurality of exhaust ducts through the interior of the MIRSS assembly in response to changes in air density due to the working fluid absorbing heat from both the reactor containment system and the collector cylinder.

[0221] Example 21: The MIRSS assembly of exemplary embodiment 20, configured to couple one or more exhaust ducts to an opening in a non-vibration-isolated exhaust of a nuclear reactor coolant system configured to direct a working fluid to the surrounding environment.

[0222] Example 22: A MIRSS assembly as described in exemplary embodiment 21, comprising a flexible duct connected between one or more exhaust ducts and an opening in a non-vibration-isolated exhaust portion of the reactor cooling system, the flexible duct configured to establish fluid communication between the vibration-isolated portion of the reactor cooling system and the non-vibration-isolated exhaust portion of the reactor cooling system.

[0223] Example 23: A MIRSS assembly as described in exemplary embodiment 22, comprising an exhaust manifold structure, the exhaust manifold structure at least partially defining one or more exhaust ducts and an outlet duct coupled to the one or more exhaust ducts, the outlet duct being configured to be coupled between the one or more exhaust ducts and the flexible duct.

[0224] Example 24: The MIRSS assembly of Exemplary Embodiment 23, wherein the exhaust manifold structure at least partially defines at least two exhaust ducts coupled in parallel with the outlet duct.

[0225] Example 25: A method of constructing a nuclear power plant, comprising: constructing a reactor building lower building structure configured to structurally support and contain a reactor containment system configured to include a nuclear reactor, the lower building structure including at least one reactor building support surface on a foundation configured to support structural loads of the reactor containment system; mounting a plurality of seismic isolation devices on at least one reactor building support surface; By constructing a Modular Isolation Reactor Support System (MIRSS) assembly, the MIRSS assembly: a cylindrical reactor support structure configured to collectively define a seismic isolation assembly within a nuclear power plant including a reactor containment system and to structurally support the reactor containment system on a plurality of seismic isolators so as to be seismically isolated from the reactor building; a collector cylinder configured to at least partially receive the reactor containment system based on the reactor containment system being structurally supported by a cylindrical reactor support structure, the collector cylinder configured to at least partially define a riser annular gap between an inner cylindrical surface of the collector cylinder and an outer sidewall surface of the reactor containment system; a bulkhead configured to at least partially define a downcomer annular gap between an outer cylindrical surface of the bulkhead and the reactor building; a plurality of exhaust ducts extending from the collector cylinder through the interior of the cylindrical reactor support structure; Mounting the MIRSS assembly on a plurality of vibration isolation devices, the MIRSS assembly defining a vibration isolation assembly within the nuclear power plant; By mounting the reactor containment system on the MIRSS assembly, The MIRSS assembly structurally supports the reactor containment system on multiple isolators, and causing the isolation assembly to include a reactor containment system.

[0226] Example 26: Completing the reactor building by constructing an upper building structure of the reactor building on the lower building structure, further comprising enclosing a reactor containment system within the reactor building; The isolation assembly is isolated from the lower and upper building structures to the isolation assembly defines a floor structure of a head access area (HAA) stored above the floor structure by an upper building structure of the reactor building, such that the floor structure is isolated from the upper building structure storing the HAA above the floor structure; 26. The method of exemplary embodiment 25, wherein the MIRSS assembly further comprises an HAA seal configured to establish a seal between the floor structure and the upper building structure.

[0227] Example 27: The lower building structure comprises a containment pit configured to at least partially receive a reactor containment system; the at least one reactor building support surface at least partially surrounds the containment pit at a top opening of the containment pit such that a plurality of seismic isolation devices are mounted on the at least one reactor building support surface and extend in a circumferential pattern around at least the periphery of the top opening of the containment pit; Mounting the MIRSS assembly on a plurality of isolators may involve lowering the MIRSS assembly at least partially into the containment pit. a MIRSS assembly structurally supported on a plurality of isolators and extending downwardly at least partially into the storage pit through a top opening of the storage pit; 26. The method of exemplary embodiment 25, wherein the MIRSS assembly is configured to structurally support the reactor containment system within the collector cylinder and extend at least partially downwardly into the containment pit.

[0228] Example 28: The method of exemplary embodiment 25, wherein the MIRSS assembly is configured to define at least one shielded chamber within the MIRSS assembly and radially outward relative to the collector cylinder, the at least one shielded chamber configured to hold at least one shielding material.

[0229] Example 29: The method of exemplary embodiment 25, wherein constructing the MIRSS assembly includes connecting a plurality of MIRSS modules together to collectively define a cylindrical reactor support structure, a collector cylinder, a bulkhead, and a plurality of exhaust ducts.

[0230] Example 30: The method of exemplary embodiment 29, wherein each MIRSS module of the plurality of MIRSS modules defines a separate azimuthal segment of the cylindrical reactor support structure, a separate azimuthal segment of the collector cylinder, and a separate azimuthal segment of the bulkhead, such that construction of the MIRSS assembly includes azimuthal coupling of the plurality of MIRSS modules together.

[0231] Example 31: The method of exemplary embodiment 29, wherein the method further includes fabricating a plurality of MIRSS modules at one or more remote locations and transporting the plurality of MIRSS modules from the one or more remote locations to the underlying building structure prior to connecting the plurality of MIRSS modules together.

[0232] Example 32: The method of exemplary embodiment 25, further comprising connecting the plurality of exhaust ducts of the MIRSS assembly to an opening in a non-vibration-isolated exhaust section of the reactor coolant system that is fluidly connected to the surrounding environment.

[0233] Example 33: The method of exemplary embodiment 32, wherein connecting the plurality of exhaust ducts to the non-vibration-isolated exhaust section comprises connecting a flexible duct between one or more of the plurality of exhaust ducts and an opening in the non-vibration-isolated exhaust section of the reactor cooling system, such that the flexible duct establishes fluid communication between the vibration-isolated section of the reactor cooling system and the non-vibration-isolated exhaust section.

[0234] Example 34: Coupling an exhaust manifold structure to a cylindrical reactor support structure such that at least a portion of the exhaust manifold structure extends through the cylindrical reactor support structure to a collector cylinder to at least partially define one or more exhaust ducts; 34. The method of exemplary embodiment 33, further comprising connecting an outlet duct of the exhaust manifold structure to the flexible duct.

Claims

1. A nuclear power plant, a reactor containment system including a nuclear reactor; a reactor building configured to structurally support the reactor containment system on a foundation and to house the reactor containment system within the reactor building; a plurality of seismic isolation devices coupled to the reactor building; a modular isolated reactor support system (MIRSS) assembly; The MIRSS assembly comprises: the MIRSS assembly defines a seismic isolation assembly within the nuclear power plant including the reactor containment system, the cylindrical reactor support structure configured to structurally support the reactor containment system on the plurality of seismic isolators so as to be seismically isolated from the reactor building; and a collector cylinder configured to at least partially receive the reactor containment system, the reactor containment system being structurally supported by the cylindrical reactor support structure, the collector cylinder configured to at least partially define a riser annular gap between an inner cylindrical surface of the collector cylinder and an outer sidewall surface of the reactor containment system; a bulkhead configured to at least partially define a downcomer annular gap between an outer cylindrical surface of the bulkhead and the reactor building, a bottom opening of the downcomer annular gap being in fluid communication with a bottom opening of the riser annular gap; a plurality of exhaust ducts extending from the collector cylinder through the interior of the cylindrical reactor support structure.

2. The MIRSS assembly includes: downwardly through the downcomer annular gap to the bottom opening of the downcomer annular gap; flowing from the bottom opening of the downcomer annular gap to the bottom opening of the riser annular gap; flowing the working fluid through the riser annular gap to the top of the riser annular gap in response to changes in air density due to the working fluid absorbing heat from both the reactor containment system and the collector cylinder; 2. The nuclear power plant of claim 1, configured to exhaust the isolation assembly by flowing through one or more of the plurality of exhaust ducts from a top of the riser annular gap through the interior of the MIRSS assembly.

3. 3. The nuclear power plant of claim 2, wherein the MIRSS assembly is configured to couple the one or more exhaust ducts to an opening in a non-vibration-isolated exhaust of a reactor coolant system configured to direct the working fluid to an ambient environment.

4. 4. The nuclear power plant of claim 3, wherein the MIRSS assembly comprises a flexible duct coupled between the one or more exhaust ducts and the opening in the non-isolated exhaust portion of the reactor coolant system, the flexible duct configured to establish fluid communication between the isolated portion of the reactor coolant system and the non-isolated exhaust portion of the reactor coolant system.

5. 3. The nuclear power plant of claim 2, wherein the MIRSS assembly comprises a plurality of MIRSS modules coupled together to collectively define the cylindrical reactor support structure, the collector cylinder, the bulkhead, and the plurality of exhaust ducts.

6. 10. The nuclear power plant of claim 1, wherein the MIRSS assembly is configured to define at least one shielded chamber within the MIRSS assembly and radially outward from the collector cylinder, the at least one shielded chamber configured to hold at least one shielding material.

7. 3. The nuclear power plant of claim 2, wherein the MIRSS assembly is configured to direct the working fluid to the downcomer annular gap via a heat transfer path that passes through at least one isolator of the plurality of isolators, thereby causing the working fluid to remove heat from the at least one isolator by the MIRSS assembly.

8. the isolation assembly defines a floor structure of a head access area (HAA) stored above a floor structure by an upper building structure of the reactor building, such that the floor structure is isolated from the upper building structure storing the HAA above the floor structure; 10. The nuclear power plant of claim 1, wherein the MIRSS assembly further comprises an HAA seal configured to establish a seal between the floor structure and the upper building structure.

9. 1. A Modular Isolation Reactor Support System (MIRSS) module configured to define an azimuthal portion of an annular structure, comprising: an upper modular structure defining a distinct azimuthal segment of the annular cylindrical reactor support structure, the upper modular structure configured to structurally support at least a portion of the structural loads of a reactor containment system including the nuclear reactor; one or more lower modular structures axially stacked below the upper modular structure, the one or more lower modular structures collectively defining distinct azimuthal segments of a partition wall of the annular structure; A MIRSS module, wherein the upper modular structure and the one or more lower modular structures have respective inner sidewall surfaces that collectively define distinct azimuthal segments of a collector cylinder of the annular structure.

10. 10. The MIRSS module of claim 9, wherein the upper modular structure is configured to at least partially define a shielded chamber within a module of the upper modular structure, and the upper modular structure is configured to retain shielding material within the shielded chamber.

11. 10. The MIRSS module of claim 9, wherein the upper modular structure is configured to at least partially define one or more exhaust ducts extending from the distinct azimuthal segments of the collector cylinder through a module interior of the upper modular structure.

12. 10. A MIRSS assembly comprising a plurality of MIRSS modules, each MIRSS module of the plurality of MIRSS modules being as defined in claim 9, the plurality of MIRSS modules being azimuthally coupled to collectively define the annular structure, such that the MIRSS assembly: the cylindrical reactor support structure of the annular structure, the cylindrical reactor support structure configured to structurally support the reactor containment system; the annular collector cylinder configured to at least partially receive the reactor containment system based on the reactor containment system being structurally supported by the cylindrical reactor support structure, the reactor containment system including the nuclear reactor, the collector cylinder configured to at least partially define a riser annular gap between an inner cylindrical surface of the collector cylinder and an outer sidewall surface of the reactor containment system; the bulkhead of the annular structure configured to at least partially define a downcomer annular gap between an outer cylindrical surface of the bulkhead and the reactor building configured to structurally support the reactor containment system on a foundation and to house the reactor containment system within the reactor building, the bottom opening of the downcomer annular gap being in fluid communication with the bottom opening of the riser annular gap; a plurality of exhaust ducts extending from said collector cylinder through the interior of said cylindrical reactor support structure.

13. The MIRSS assembly includes: downwardly through the downcomer annular gap to the bottom opening of the downcomer annular gap; flowing from the bottom opening of the downcomer annular gap to the bottom opening of the riser annular gap; flowing the working fluid through the riser annular gap to the top of the riser annular gap in response to changes in air density due to the working fluid absorbing heat from both the reactor containment system and the collector cylinder; 13. The MIRSS assembly of claim 12, configured to exhaust from the MIRSS assembly by flowing through one or more exhaust ducts of the plurality of exhaust ducts from the top of the riser annular gap through the interior of the MIRSS assembly.

14. 14. The MIRSS assembly of claim 13, wherein the MIRSS assembly is configured to couple the one or more exhaust ducts to an opening in a non-vibration-isolated exhaust of a nuclear reactor coolant system configured to direct the working fluid to an ambient environment.

15. 15. The MIRSS assembly of claim 14, wherein the MIRSS assembly comprises a flexible duct coupled between the one or more exhaust ducts and the opening in the non-isolated exhaust portion of the reactor cooling system, the flexible duct configured to establish fluid communication between the isolated portion of the reactor cooling system and the non-isolated exhaust portion of the reactor cooling system.

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