Nuclear reactor facility integrated with passive air cooling system

Abstract

A nuclear reactor facility may include a reactor building, a reactor vessel contained within the reactor building, and an auxiliary cooling system integrated with the reactor building. The reactor building has a visible section above ground level and a buried section below ground level. The reactor vessel contains a fuel core and is contained within the buried section of the reactor building below ground level. The auxiliary cooling system includes a plurality of ducts integrated with the reactor building and is configured to passively cool the reactor vessel via natural air circulation.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority under 35 U.S.C. § 119 of U.S. Provisional Application No. 63 / 174,339, filed April 13, 2021, the entire contents of which are incorporated herein by reference.

[0002] This disclosure relates to passive cooling of pool-type metal-cooled, salt-cooled or gas-cooled nuclear reactors, where the passive cooling system is integrated into the reactor building. [Background technology]

[0003] When operating a nuclear reactor to generate electricity, it may be necessary to perform a shutdown for planned maintenance or an emergency. A shutdown may involve inserting neutron-absorbing control rods into the fissile fuel core. However, despite the insertion of the control rods, the decay of the fuel still continues to produce a significant amount of heat that must be dissipated from the reactor.

[0004] The thermal capacity of the coolant (e.g., sodium, fluoride salts, chloride salts, sodium-potassium) coolant and adjacent structures aid in the dissipation of residual heat. However, the structural materials of the reactor may not be able to safely withstand the relatively high temperatures for extended periods of time. For example, the metals of the reactor vessel may fail as a result of high temperature creep, or the walls of the housing silo may splay and crack when exposed to relatively high temperatures. As a result, auxiliary cooling systems are commonly utilized to remove heat from the reactor during shutdowns. Summary of the Invention [Problem to be solved by the invention]

[0005] Various energy-driven cooling systems may be utilized to dissipate heat from the reactor. However, the supply of energy to such cooling systems may cause the cooling systems themselves to fail. For example, pumps and ventilation systems configured to cool the reactor core may fail. Additionally, when operator intervention is required, there are foreseeable scenarios in which the operator may not be able to provide the appropriate action. [Means for solving the problem]

[0006] At least one embodiment relates to a nuclear reactor facility. In an exemplary embodiment, the nuclear reactor facility may include a reactor building having a visible section above ground level and a buried section below ground level, a reactor vessel including a fuel core and contained within the buried section of the reactor building below ground level, and an auxiliary cooling system integrated with the reactor building and including a plurality of ducts configured to passively cool the reactor vessel via natural air circulation.

[0007] The reactor building may define a refueling access area and a head access area below the refueling access area.

[0008] The refueling access area may be above ground level and the head access area may be below ground level.

[0009] The refueling access area may include a refueling access floor and the head access area may include a head access floor below the refueling access floor.

[0010] The refueling access floor may define an opening and may include a floor plug rotatably mounted within the opening, the floor plug configured to allow access to the reactor vessel via rotation of the floor plug.

[0011] The floor plugs may be in the form of a primary floor plug and a secondary floor plug concentrically integrated with the primary floor plug, the primary floor plug defining at least one primary port and the secondary floor plug defining at least one secondary port, the primary floor plug and the secondary floor plug configured to allow access to the reactor vessel via independent rotation of at least the primary floor plug or the secondary floor plug.

[0012] The reactor building may include a number of structural sleeves between the refueling access floor and the head access floor, the number of structural sleeves configured to support the refueling access floor while allowing a number of ducts of the auxiliary cooling system to pass therethrough.

[0013] The reactor building may include radial floor beams embedded in at least one of the refueling access floor or the head access floor.

[0014] The radial floor beams may include a plurality of diametrically opposed beams disposed about a central longitudinal axis of the reactor vessel.

[0015] Each of the multiple ducts of the auxiliary cooling system may extend between an adjacent pair of radial floor beams (or even multiple ducts may extend between a pair of radial beams).

[0016] Each of the plurality of ducts of the auxiliary cooling system may have a trapezoidal cross-section and may be oriented to correspond to a truncated wedge-shaped space defined by adjacent radial floor joists.

[0017] The auxiliary cooling system may include a hot plenum ring header positioned below the head access floor and about the reactor vessel, the hot plenum ring header configured to collect heated air rising along the reactor vessel.

[0018] The multiple ducts of the auxiliary cooling system may include an inlet duct and an outlet duct, and the hot plenum ring header may be connected and configured to direct the heated air to the outlet duct.

[0019] The auxiliary cooling system may define a cold plenum below the head access floor, and the inlet duct may be configured to channel cooling air to the cold plenum.

[0020] The auxiliary cooling system may include a cold plenum ring header disposed below the hot plenum ring header and connected to the inlet duct.

[0021] The cold plenum ring header may be configured to channel cooling air from the inlet duct to the riser annulus adjacent the reactor vessel.

[0022] The visible and buried sections of the reactor building may have a continuous cylindrical form.

[0023] The buried section of the reactor building may include a first wing extension configured to facilitate routing of at least one of piping or cabling from the reactor building to an adjacent building.

[0024] The buried section of the reactor building may include a second wing extension disposed opposite the first wing extension.

[0025] The multiple ducts of the auxiliary cooling system may extend through one or more side walls of the reactor building.

[0026] The multiple ducts may be arranged in an array that follows the outer contour of the circular cross-section of the reactor vessel. In one example, the inlet and / or outlet ducts may be equidistantly (e.g., concentrically) arranged about a central longitudinal axis of the reactor vessel.

[0027] The buried section of the reactor building may include a cylindrical silo, and the multiple ducts may be arranged in an array that follows the inner contour of the circular cross-section of the cylindrical silo. In one example, the inlet duct and / or the outlet duct may be arranged equidistantly (e.g., concentrically) around a central longitudinal axis of the cylindrical silo.

[0028] The multiple ducts may be arranged in opposing arrays of circular segments (e.g., arcs) about the reactor vessel. In one example, the opposing arrays of circular segments may be concentric with a central longitudinal axis of the reactor vessel.

[0029] Various features and advantages of the non-limiting embodiments herein will 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 to be drawn to scale unless specifically noted otherwise. For clarity, various dimensions of the drawings may be exaggerated. [Brief description of the drawings]

[0030] [Figure 1] 1 is a cross-sectional view of a nuclear reactor facility in accordance with an illustrative embodiment; [Diagram 2] FIG. 1 is a plan view of a head access area of ​​a nuclear reactor facility illustrating three potential wing designs in accordance with an example embodiment. [Diagram 3] FIG. 1 illustrates a perspective view of a ducted hot plenum ring header and adjacent radial floor beams according to an exemplary embodiment; [Figure 4] FIG. 1 is a plan view of a silo floor level below a head access area of ​​a nuclear reactor facility illustrating two potential cold plenum designs according to an example embodiment. [Diagram 5] 1 is a cross-sectional view of a cold plenum of a nuclear reactor facility in accordance with an exemplary embodiment. [Figure 6] FIG. 2 is a top view of a floor plug and an underlying reactor head accessed through the floor plug in accordance with an exemplary embodiment; [Figure 7] 1 is a cross-sectional view of a head access area of ​​a nuclear reactor facility in accordance with an exemplary embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031] Several detailed exemplary embodiments are disclosed herein. However, the specific structural and functional details disclosed herein are merely representative for purposes of describing the exemplary embodiments. However, the exemplary embodiments may be embodied in many alternative forms and should not be construed as being limited to only the exemplary embodiments described herein.

[0032] Thus, while exemplary embodiments are susceptible to various modifications and alternative forms, exemplary embodiments thereof have been shown by way of example in the drawings and are described in detail herein. It is to be understood, however, that there is no intention to limit the exemplary embodiments to the particular forms disclosed, but on the contrary, the exemplary embodiments encompass all modifications, equivalents, and alternative forms thereof. Like reference numerals refer to like elements throughout the description of the drawings.

[0033] When an element or layer is referred to as "on," "connected," "coupled," "attached," "adjacent," or "covering" another element or layer, it is understood that it can be directly on, connected, coupled, attached, adjacent, or covering the other element or layer, or there may be intervening elements or layers. In contrast, when an element is referred to as "directly on," "directly connected," 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 or subcombinations of one or more of the associated listed items.

[0034] Terms such as first, second, third, etc. may be used herein to describe various elements, regions, layers, and / or sections, but it should be understood that these elements, regions, layers, and / or sections should not be limited by these terms. These terms are used only to distinguish one element, region, layer, or section from another region, layer, or section. Thus, a first element, region, layer, or section described below can be called a second element, region, layer, or section without departing from the teachings of the exemplary embodiments.

[0035] Spatially relative terms (e.g., "beneath," "below," "lower," "above," "upper," etc.) may be used herein for ease of description to describe the relationship of one element or feature to another element(s) or feature(s) as shown in the figures. It should be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, an element described as "below" or "below" the other element or feature would be oriented "above" the other element or feature. Thus, the term "below" can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein would be interpreted accordingly.

[0036] The terms used herein are for the purpose of describing various exemplary embodiments only and are not intended to limit the exemplary embodiments. As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms unless the context clearly indicates otherwise. It will be further understood that the terms "comprise," "including," "comprises," and / or "comprising," as used herein, specify the presence of stated features, integers, steps, operations, and / or elements, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, and / or groups thereof.

[0037] When the terms "about" or "substantially" are used herein in connection with numerical values, the associated numerical values ​​are intended to include manufacturing or operating tolerances (e.g., ±10%) around the stated numerical values. Furthermore, when the terms "generally" or "substantially" are used in connection with geometric shapes, precision of the geometric shapes is not required, but freedom of shape is intended to be within the scope of the present disclosure. Furthermore, regardless of whether a numerical value or shape is modified as "about," "generally," or "substantially," it will be understood that these values ​​and shapes should be interpreted as including manufacturing or operating tolerances (e.g., ±10%) around the stated numerical values ​​or shapes.

[0038] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by those skilled in the art to which the exemplary embodiments belong. Terms, including those defined in commonly used dictionaries, should be interpreted to have a meaning consistent with their meaning in the context of the relevant art, and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

[0039] The processing circuitry may be hardware including logic circuits, a hardware / software combination such as a processor executing software, or a combination thereof. For example, the processing circuitry may more specifically include, but is not limited to, a central processing unit (CPU), an arithmetic logic unit (ALU), a digital signal processor, a microcomputer, a field programmable gate array (FPGA), a system on a chip (SoC), a programmable logic unit, a microprocessor, an application specific integrated circuit (ASIC), and the like.

[0040] 1 is a cross-sectional view of a nuclear reactor facility in accordance with an example embodiment. Referring to FIG. 1, a nuclear reactor facility 1000 may include an auxiliary cooling system 300 integrated with a reactor building 100 (or building housing). The auxiliary cooling system 300 is configured to passively cool a reactor vessel 200 via natural air circulation. As shown, the auxiliary cooling system 300 includes a number of ducts configured to dissipate heat from the reactor vessel 200. In particular, the number of ducts of the auxiliary cooling system 300 includes an inlet duct 310 and an outlet duct 340.

[0041] During operation of the auxiliary cooling system 300, cooling air (e.g., outside, ambient air) enters the reactor facility 1000 via the inlet duct 310, while heated air from the vicinity of the reactor vessel 200 exits the reactor facility 1000 via the outlet duct 340. Notably, the auxiliary cooling system 300 is passive in that no power source (e.g., electricity) is required for its operation. Instead, the auxiliary cooling system 300 operates automatically via natural air circulation based on the different densities of the cooling air and the heated air. Specifically, heated air rising from the reactor vessel 200 and exiting the reactor facility 1000 via the outlet duct 340 creates a natural air circulation, where the cooling air is drawn into the reactor facility 1000 via the inlet duct 310 and descends into the cold plenum 320. The rising heated air collected by the hot plenum ring header 330 is directed to the outlet duct 340 to sustain the natural air circulation cycle.

[0042] The ducts of the auxiliary cooling system 300 may be vertical structures with bends / angles at their top sections so that they extend through the sidewalls (opposite the ceiling) of the reactor building 100. In an exemplary embodiment, such an inclined configuration of the ducts provides the necessary clearance for an overhead crane (which may also be referred to as a bridge crane) to be installed within the reactor building 100 so as to be above the ducts. The overhead crane may include a parallel runway, a traveling bridge, and a winch. The parallel runway of the overhead crane may be attached to opposing sidewalls of the reactor building 100 (e.g., the same sidewall through which the ducts extend) such that the traveling bridge spans the gap. The winch, which is the lifting part of the overhead crane, is configured to move along the traveling bridge. During operation of the overhead crane (e.g., for refueling), when the traveling bridge is considered to be moving along the parallel runway in the x direction, the winch may be considered to be moving in the y direction, and the object being lifted may be considered to be moving in the z direction.

[0043] The multiple ducts of the auxiliary cooling system 300 may be arranged in opposing quadrants around the reactor head 210 such that opposing spaces in adjacent quadrants (without ducts) provide increased access to the reactor vessel 200. However, it should be understood that the exemplary embodiment is not so limited. In addition, while four inlet ducts 310 and two outlet ducts 340 are shown in FIG. 1, it should be understood that other combinations are possible. Furthermore, the inlet ducts 310 and outlet ducts 340 may be alternatively arranged (e.g., inlet duct 310, outlet duct 340, inlet duct 310, outlet duct 340, etc.). The outlet opening of the outlet duct 340 may be higher than the inlet opening of the inlet duct 310. In such a case, the possibility of heated air exiting the outlet duct 340 being inadvertently drawn into the inlet duct 310 along with the cooling air may be reduced or prevented.

[0044] Reactor building 100 has a visible section 110 above ground level and a buried section 120 below ground level. Reactor vessel 200 contains the fuel core and is contained (e.g., deeply buried) within buried section 120 of reactor building 100 below ground level. Auxiliary cooling system 300 may be a radiant vessel auxiliary cooling system, although example embodiments are not so limited. Integration of auxiliary cooling system 300 with building design, as described in more detail herein, may reduce the cost and schedule of the overall nuclear power plant design while meeting basic safety function requirements for long term heat removal from the reactor core.

[0045] The reactor may be a pool-type design with top inlets for components where the choice of coolant is not a limitation of this disclosure. In an exemplary embodiment, the reactor pool is located underground in a silo near the central axis with one or more floors above the reactor top. The floors below ground level are collectively referred to as the head access area 122. The bottom flow, however, is referred to as the silo cold plenum, while the beds above ground level are collectively referred to as the refueling access area 112.

[0046] The reactor may be supported vertically on top, with the reactor pool vessel suspended from the head access area floor, and optionally laterally restrained at a lower location along its length. However, it should be understood that this additional lateral restraint is not required in all embodiments. Additionally, the present disclosure is not limited to the reactor being supported vertically on top. For example, in alternative examples, the reactor may be supported vertically at the bottom. Additionally, in other examples, the reactor may be supported vertically at another axial location along its length.

[0047] The refueling access area 112 of the reactor building 100 includes a refueling access floor 114, and the head access area 122 of the reactor building 100 includes a head access floor 124. The head access floor 124 is below the refueling access floor 114. In an exemplary embodiment, a floor plug 140 is disposed in the opening 130 to form a portion of the refueling access floor 114. The floor plug 140 may include smaller access ports to allow vertical access to the reactor head mounted equipment directly below. For example, the floor plug 140 as well as the smaller access ports are rotatable, thereby minimizing the total number of access ports since one port can be positioned above many reactor head equipment locations by rotating its parent port or plug.

[0048] The multiple ducts of the auxiliary cooling system 300 pass through the refueling access area floor 114 and also through the head access area floor 124. In an exemplary embodiment, one or more structural sleeves (e.g., structural sleeve 170 of FIG. 7 ) are provided between the refueling access area floor 114 and the head access area floor 124. In such a case, the structural sleeve acts as a column supporting the refueling access area floor 114 while allowing the multiple ducts of the auxiliary cooling system 300 to pass through the structural sleeve. As a result, the refueling access area floor 114 may have a thinner and stiffer construction.

[0049] The above-ground reactor building 100 profile may be a continuation of the underground circular / cylindrical profile, or the reactor building 100 profile may be a step-out profile with a larger circular, square, or rectangular footprint above ground to improve access to or accommodate more equipment.

[0050] In an exemplary embodiment, the profile of the underground reactor building 100 is a straight cylindrical shape. In such a case, a straight excavation (as opposed to a stepped excavation) is included. Despite the larger volume compared to a stepped design, construction is faster and the symmetry and round shape improve robustness against seismic events. In addition, much or most of the auxiliary equipment may be intentionally left out of the reactor building 100. This reduces project costs as the reactor building 100 is built to a higher tier nuclear standard. Essentially, in some instances, the building only houses the reactor module itself, the equipment installed within the reactor, ducts associated with air cooling of the reactor, HVAC, and cranes.

[0051] FIG. 2 includes a plan view of the head access area of ​​a nuclear reactor facility showing three potential wing designs according to an exemplary embodiment. As shown in FIG. 2, the profile of the underground reactor building may not be a straight cylinder. The single and double wing designs for the nuclear reactor facility 1000'' and the nuclear reactor facility 1000' each incorporate a small keyway that extends from ground level to the bottom of the head access area level. For example, the keyway 126a'' may be oriented at 0° for the single wing design in the nuclear reactor facility 1000'', and the opposing keyways 126a' and 126b' may be oriented at 0° and 180° for the double wing design in the nuclear reactor facility 1000'. In an exemplary embodiment, these keyways simply protrude from a straight cylindrical profile to facilitate underground routing of the major / main process lines 128a' / 128a'' or auxiliary lines 128b' / 128b'' (e.g., piping and / or cabling) from the reactor buildings 100' and 100'' to adjacent auxiliary buildings. Examples of auxiliary systems include primary coolant purge, cover gas purge, or additional heat removal systems. The space provided by the keyway(s) also allows the design more room for safety-related isolation valves, if necessary (which may otherwise require a larger silo diameter). On the other hand, the zero-wing design in the reactor facility 1000'' may be implemented for configurations where the passage of the major / main process lines 128a''' or auxiliary lines 128b''' (e.g., piping and / or cabling) does not need to exit the buried section of the reactor building 100''' to transition to an adjacent underground building (instead, the lines are directed upward to above ground level before transitioning to an adjacent building). In all wing designs, most of the power and control cabling, HVAC ducts, HVAC piping, elevator access, stairwells, etc. may enter the head access area through the refueling access area floor. The space between the reactor cooling ducts may also be utilized for these interconnections. The inlet ducts 310' / 310'' / 310'' may be as described above in connection with the inlet duct 310 of FIG. 1.Similarly, the outlet ducts 340' / 340'' / 340'' may be as described above in relation to the outlet duct 340 of Figure 1. As a result, the relevant details of the ducts will not be repeated for the sake of brevity.

[0052] FIG. 3 is a perspective view of a hot plenum ring header with ducts connected thereto and adjacent radial floor beams according to an exemplary embodiment. Referring to FIG. 3, the reactor building includes radial floor beams 125 configured to support the head access area floor. For example, the radial floor beams 125 may include multiple diametrically opposed beams disposed about the center of the hot plenum ring header 330' or the center longitudinal axis of the reactor vessel. The radial floor beams 125 may be I-beams or H-beams. Additionally, the radial floor beams 125 may be embedded in concrete. The radial floor beams 125 may be used to support the refueling access area floor as well.

[0053] When the nuclear reactor facility is constructed, each of the plurality of ducts 332 of the auxiliary cooling system extends between an adjacent pair of radial floor beams 125 of the reactor building. Referring back to FIG. 3, each of the plurality of ducts 332 (e.g., outlet ducts) connected to the hot plenum ring header 330′ extends radially outward until it reaches a suitable clearance before extending upward (e.g., like the outlet duct 340 of FIG. 1) between an adjacent pair of radial floor beams 125 of the reactor building. Thus, at least in this regard, the auxiliary cooling system may be integrated with the reactor building in that the structure of the auxiliary cooling system is interspersed with the structure of the reactor building (e.g., a reactor building based on a cylindrical silo deeply embedded in a corresponding shaft).

[0054] The cross-section of the plurality of ducts 332 may be circular, triangular, square, rectangular, or trapezoidal. As shown in FIG. 3, the distal / outer ends of the radial floor beams 125 are spaced further apart relative to the proximal / inner ends closer to the center of the hot plenum ring header 330' (or the central longitudinal axis of the reactor vessel). Taking this geometry into account, the cross-section of the plurality of ducts 332 of the auxiliary cooling system may be configured to better utilize this space. For example, the cross-section of the plurality of ducts 332 may have a trapezoidal shape to increase the available airflow area taking into account the truncated wedge space defined by adjacent radial floor beams 125.

[0055] FIG. 4 includes a plan view of the silo floor level below the head access area of ​​the nuclear reactor facility showing two potential cold plenum designs according to an exemplary embodiment. Referring to FIG. 4, in the silo cold plenum design of the nuclear reactor facility 2000', the inlet duct (for cooling air) is configured to terminate just below the head access area floor and discharge the cooling air into the silo cold plenum 320'. A cold plenum is also shown, for example, in FIG. 1. In such a case, the head access area floor may be supported by the silo wall 150' and also by the pedestal 160' that surrounds the reactor vessel 200' (or reactor module) with a relatively close-fitting annular gap. The outer annulus defined by the inner diameter of the silo wall 150' and the outer diameter of the reactor pedestal 160' is considered the silo cold plenum 320'. The cooling air from the inlet duct of the auxiliary cooling system flows downward into this space. The inner annulus formed by the outer diameter of the reactor vessel 200' (or reactor module) and the inner diameter of the reactor pedestal 160' is considered the hot air riser. The inner diameter of the reactor pedestal 160' may contain a collector cylinder with many possible heat transfer enhancement mechanisms. This is in the hot air riser where safety related long term heat removal is dissipated to the air which is the ultimate heat sink driven by natural circulation through the passive reactor vessel cooling system. The heated air in the hot air riser is collected in a hot plenum ring header (e.g., FIG. 3) directly below the head access area floor. The hot plenum ring header is configured to direct the heated air to the auxiliary cooling system outlet duct which exhausts the heated air out of the reactor building.

[0056] Alternatively, in the ring cold plenum design of reactor facility 2000'', the flow path of the heated air is the same, but the flow path of the cooling air is different. For example, instead of the auxiliary cooling system inlet duct terminating below the head access area floor, the inlet duct continues to the bottom of the silo where the cooling air discharges to a common ring header (cold plenum ring header 322), which supplies cooling air to the hot air riser annulus surrounding reactor vessel 200''. In some exemplary embodiments, the ring cold plenum design can provide better performance due to reduced expansion losses.

[0057] FIG. 5 is a cross-sectional view of a cold plenum of a nuclear reactor facility according to an exemplary embodiment. Referring to FIG. 5, as described above, cooling air from outside the reactor building is first drawn into the reactor building and directed downward to the cold plenum 320″. For example, ambient air (above ground level) as cooling air may first enter the inlet duct of the auxiliary cooling system. The cooling air may then flow downward through a 45° bend and transition vertically and downward through the refueling access area floor and the head access area floor. The inlet duct may be interrupted as the cooling air is discharged to the cold plenum 320″ below the head access area floor or the lower operating floor (silo cold plenum design). The cooling air continues to the bottom of the silo where the flow enters the annulus inlet, which is an opening between the cold plenum columns 162 of the reactor pedestal 160″. Once in the pedestal 160'', the cooling air flow is directed upward into the annulus defined by the reactor module vessel surface and the collector cylinder (not shown, but attached to the pedestal 160'') where it becomes the heated air flow. Before the heated air flow reaches the top / head of the reactor, the heated air is discharged horizontally into a hot plenum ring header (e.g., FIG. 3). The heated air flow then splits from the hot plenum ring header to distribute the split heated air flow to several outlet ducts (e.g., hot air stack ducts) that rise through the head access area floor and the refueling access area floor. The heated air exits the reactor building through an outlet duct at an elevation above the inlet duct for the cooling air. Because the heated air rises, the possibility of the heated air being inadvertently drawn into the inlet duct with the cooling air is reduced or prevented due to the elevation difference of the outlet duct relative to the inlet duct.

[0058] FIG. 6 includes a plan view of a floor plug and an underlying reactor head accessed through the floor plug according to an exemplary embodiment. With reference to FIG. 6, the floor plug 140' may be in the form of a primary floor plug 142 (or main floor plug) that is rotatably configured and a secondary floor plug 144 that is rotatably assembled with the primary floor plug 142 to allow independent rotation of the primary floor plug 142 and the secondary floor plug 144. In a nuclear reactor facility, the floor plug 140' forms part of a refueling access floor and is located directly above or perpendicular to the reactor head 210'. For example, in one example, the refueling access floor defines an opening above the reactor head 210' that is configured to hold or otherwise accommodate the floor plug 140' while allowing the floor plug 140' to rotate at least a full 360° in either a clockwise or counterclockwise direction. The floor plug 140' defines ports having different sizes, shapes, quantities, and locations to increase ease of access to the underlying reactor head 210'.

[0059] 6, the primary floor plug 142 may define a relatively large elongated port 143a configured to allow access to larger components on the reactor head 210' (e.g., pump 212, heat exchanger 214) when the primary floor plug 142 is rotated to provide proper alignment between the relatively large elongated port 143a and the components on the reactor head 210' to which access is desired. The relatively large elongated port 143a may have a rectangular shape (e.g., a rounded rectangular shape) and may be located closer to the periphery of the primary floor plug 142 than to the center of the floor plug 140', although example embodiments are not limited thereto.

[0060] The primary floor plug 142 may further define an intermediate sized port 143b (compared to the larger elongated port 143a described above) configured to allow access to the various components 216 on the reactor head 210'. The intermediate sized port 143b may have a circular shape and may be located approximately midway between the perimeter of the primary floor plug 142 and the center of the floor plug 140', although example embodiments are not limited thereto.

[0061] The secondary floor plug 144 may define a smaller, elongated port 145a (compared to the relatively larger, elongated port 143a described above) that is configured to allow access to other components 219 on the reactor head 210' when the secondary floor plug 144 rotates to provide proper alignment between the smaller, elongated port 145a and the components 219 on the reactor head 210' to which access is desired. The smaller, elongated port 145a may have an oval or rectangular shape (e.g., a rounded rectangular shape) and may be located closer to the periphery of the secondary floor plug 144 than to the center of the secondary floor plug 144, although example embodiments are not limited thereto.

[0062] The secondary floor plug 144 may further define a group of ports 145b configured to allow access to one or more control rods 218. The group may include three circular ports 145b positioned slightly off-center, although the example embodiment is not so limited. Although various configurations and combinations are disclosed above with respect to the size, shape, quantity, and location of the ports defined by the primary floor plug 142 and the secondary floor plug 144, it should be understood that other configurations and combinations are possible depending on the type and layout of the underlying reactor head 210' components.

[0063] FIG. 7 is a cross-sectional view of a head access area of ​​a nuclear reactor facility according to an example embodiment. Referring to FIG. 7, one or more structural sleeves 170 may be disposed between the refueling access area (RAA) floor 114' and the head access area (HAA) floor 124'. The structural sleeves 170 are configured to support the refueling access area floor 114' while passing multiple ducts (e.g., the outlet duct 342 and / or the inlet duct 312) of the auxiliary cooling system. As a result, the refueling access area floor 114' may have a thinner and more rigid structure. In one example, each of the structural sleeves 170 may be in the form of a hollow cylinder. Alternatively, in another example, each of the structural sleeves 170 may have a different form that corresponds more to the cross-sectional shape of the duct (e.g., a sleeve having a square, rectangular, or trapezoidal cross section). In FIG. 7, the outlet duct 342 (e.g., a high temperature duct) is shown extending through the structural sleeve 170. In particular, although not shown, it should be understood that the inlet duct 312 (e.g., a cold duct) may also extend through the structural sleeve 170. As previously mentioned, cooling air discharged from the inlet duct(s) 312 enters an annulus defined in part by the reactor vessel 200''' where it becomes heated air that is directed to the outlet duct(s) 342 (e.g., via a hot plenum ring header).

[0064] Although several exemplary embodiments are disclosed herein, it should be understood that other variations may be possible. Such variations are not to be regarded as departures from the spirit and scope of the present disclosure, and all such modifications as would be apparent to one skilled in the art are intended to be included within the scope of the following claims.

Claims

1. A nuclear reactor facility, a reactor building having a visible section above ground level and a buried section below said ground level; a reactor vessel containing a fuel core and contained within the buried section of the reactor building below the ground level; an auxiliary cooling system including a plurality of ducts integrated with the reactor building and configured to passively cool the reactor vessel via natural air circulation, the plurality of ducts of the auxiliary cooling system including an inlet duct and an outlet duct, the inlet duct configured to direct cooling air to a cold plenum defined by an inner surface of a silo wall and an outer surface of a reactor pedestal; Equipped with A nuclear reactor facility, wherein the buried section has a cross-section that is a rectilinear cylinder defined by the silo walls.

2. 10. The nuclear reactor facility of claim 1, wherein the reactor building defines a refueling access area and a head access area below the refueling access area.

3. 3. The nuclear reactor facility of claim 2, wherein the refueling access area is at or above ground level and the head access area is below ground level.

4. 3. The nuclear reactor facility of claim 2, wherein the refueling access area includes a refueling access floor and the head access area includes a head access floor below the refueling access floor.

5. A nuclear reactor facility, comprising: a reactor building having a visible section above ground level and a buried section below said ground level; a reactor vessel containing a fuel core and contained within the buried section of the reactor building below the ground level; an auxiliary cooling system integrated with the reactor building and including a plurality of ducts configured to passively cool the reactor vessel via natural air circulation; Equipped with the reactor building defines a refueling access area and a head access area below the refueling access area; the refueling access area includes a refueling access floor, and the head access area includes a head access floor below the refueling access floor; 1. A nuclear reactor facility, wherein the refueling access floor defines an opening and includes a floor plug rotatably mounted within the opening, the floor plug configured to provide access to the reactor vessel via rotation of the floor plug.

6. 6. The nuclear reactor facility of claim 5, wherein the floor plugs are in the form of a primary floor plug and a secondary floor plug concentrically mounted therewith, the primary floor plug defining at least one primary port and the secondary floor plug defining at least one secondary port, and the primary floor plug and the secondary floor plug configured to provide access to the reactor vessel via independent rotation of at least the primary floor plug or the secondary floor plug.

7. 5. The nuclear reactor facility of claim 4, wherein the reactor building includes a plurality of structural sleeves between the refueling access floor and the head access floor, the plurality of structural sleeves configured to support the refueling access floor while allowing the plurality of ducts of the auxiliary cooling system to pass therethrough.

8. 5. The nuclear reactor facility of claim 4, wherein said reactor building includes radial floor beams embedded in at least one of said refueling access floor or said head access floor.

9. 9. The nuclear reactor facility of claim 8, wherein said radial floor beams include a plurality of diametrically opposed beams disposed about a central longitudinal axis of said reactor vessel.

10. each of the plurality of ducts of the auxiliary cooling system includes a plurality of inlet ducts and a plurality of outlet ducts; 9. The nuclear reactor facility of claim 8, wherein said plurality of outlet ducts extend radially outward between adjacent pairs of said radial floor beams.

11. A nuclear reactor facility, comprising: a reactor building having a visible section above ground level and a buried section below said ground level; a reactor vessel containing a fuel core and contained within the buried section of the reactor building below the ground level; an auxiliary cooling system integrated with the reactor building and including a plurality of ducts configured to passively cool the reactor vessel via natural air circulation; Equipped with the reactor building defines a refueling access area and a head access area below the refueling access area; the refueling access area includes a refueling access floor, and the head access area includes a head access floor below the refueling access floor; the reactor building includes radial floor beams embedded in at least one of the refueling access floor or the head access floor; each of the plurality of ducts of the auxiliary cooling system extends between adjacent pairs of the radial floor joists; 11. A nuclear reactor facility, wherein each of the plurality of ducts of the auxiliary cooling system has a trapezoidal cross-section and is oriented to correspond to a truncated wedge-shaped space defined by adjacent radial floor beams.

12. 5. The nuclear reactor facility of claim 4, wherein the auxiliary cooling system includes a hot plenum ring header disposed below the head access floor and about the reactor vessel, the hot plenum ring header configured to collect heated air rising along the reactor vessel.

13. The nuclear reactor facility of claim 12, wherein the high temperature plenum ring header is connected and configured to direct the heated air to the outlet duct.

14. The nuclear reactor facility of claim 13 , wherein the cold plenum is disposed below the head access floor.

15. 14. The nuclear reactor facility of claim 13, wherein the auxiliary cooling system includes a cold plenum ring header disposed below the hot plenum ring header and connected to the inlet duct.

16. 16. The nuclear reactor facility of claim 15, wherein the cold plenum ring header is configured to direct cooling air from the inlet duct to a riser annulus adjacent the reactor vessel.

17. 6. The nuclear reactor facility of claim 5, wherein the visible section and the buried section of the reactor building have a continuous cylindrical configuration.

18. 20. The nuclear reactor facility of claim 17, wherein the buried section of the reactor building includes a first wing extension configured to facilitate a path for at least one of piping or cabling to pass from the reactor building to an adjacent building.

19. 20. The nuclear reactor facility of claim 18, wherein the buried section of the reactor building includes a second wing extension disposed opposite the first wing extension.

20. 2. The nuclear reactor facility of claim 1, wherein the plurality of ducts of the auxiliary cooling system extend through one or more side walls of the reactor building.

21. 2. The nuclear reactor facility of claim 1, wherein the plurality of ducts are arranged in an array that follows an outer contour of a circular cross section of the reactor vessel.

22. 2. The nuclear reactor facility of claim 1, wherein the buried section of the reactor building includes a cylindrical silo, and the plurality of ducts are arranged in an array that follows an inner contour of a circular cross section of the cylindrical silo.

23. 2. The nuclear reactor facility of claim 1, wherein the plurality of ducts are arranged in opposing arrays of circular segments about the reactor vessel.

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