Steam generator systems, tube sheet assemblies and reactor systems

Abstract

A steam generator system including a tube sheet assembly, such as for use in a nuclear reactor system, and related devices and methods are disclosed. An exemplary steam generator system may be installed in a reactor vessel arranged to receive a primary coolant. The steam generator system may include a tube sheet assembly defining a plenum. The tube sheet assembly includes a tube sheet and a flexible connection coupling the tube sheet to the reactor vessel. The tube sheet may include a plurality of perforations fluidly coupled to the plenum. The steam generator system may further include a plurality of heat transfer tubes fluidly coupled to the perforations and configured to receive a flow of secondary coolant. The connection may be more flexible than the tube sheet and reactor vessel to reduce stresses in the tube sheet and at connections between the heat transfer tubes and the tube sheet (e.g., tube-to-tube sheet (TTS) welds) during operation of the nuclear reactor system.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Provisional Patent Application No. 63 / 282,053, filed November 22, 2021, entitled "Stress Relief Attachment of Tubes to Tubesheets in Pressure Vessel Shells of Nuclear Reactor Power Systems," which is incorporated herein by reference in its entirety.

[0002] Federally Sponsored Research and Development This invention was made with government support under Contract No. DE-NE-000-8928 awarded by the Department of Energy. The government has certain rights in this invention.

[0003] The present invention relates to steam generator systems including tube sheet assemblies used, for example, in nuclear power reactor systems. More particularly, the present invention relates to stress relief attachments for attaching tube sheets to reactor vessels. [Background technology]

[0004] Nuclear reactor systems often include one or more steam generators located within a reactor vessel. The reactor vessel contains a reactor core and a primary coolant that absorbs heat generated from nuclear reactions (e.g., nuclear fission reactions) within the reactor core. Such steam generators may include multiple tubes (e.g., helical tubes) within the reactor vessel extending between a feedwater header and a steam header. A secondary coolant (e.g., water) enters the tubes at the feedwater header, rises through the tubes, is converted to steam (e.g., steam) as the secondary coolant absorbs heat from the primary coolant, and exits the tubes at the steam header for use in the power conversion system. The multiple tubes may be connected to a tube sheet, such as a perforated plate, at and / or adjacent to the feedwater header and / or steam header (e.g., via tube-to-tubesheet (TTS) welds). The tube sheet may be integral with or attached to the reactor vessel.

[0005] Large stresses can develop locally in the tubesheet and / or tube-to-tubesheet (TTS) welds due to incompatible movement of the tubesheet and reactor vessel under pressure and thermal loads caused by the different geometries of the tubesheet and reactor vessel. As the reactor system undergoes transient conditions, including start-up and shutdown, the stresses in the tubesheet can become cyclical, leading to fatigue and premature retirement of the steam generator. [Brief explanation of the drawings]

[0006] Many aspects of the present technology can be better understood with reference to the following drawings, in which the components are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the present technology.

[0007] [Figure 1] 1 is a partially schematic, partially cross-sectional view of a nuclear reactor system configured in accordance with an embodiment of the present technique; [Figure 2A] 1 is a cross-sectional side view of a nuclear reactor system including a steam generator system configured in accordance with an embodiment of the present technique; [Figure 2B] FIG. 2B is an enlarged cross-sectional side view of an upper tube sheet assembly of the steam generator system of FIG. 2A in accordance with an embodiment of the present technique. [Figure 3A] FIG. 2B is an enlarged cross-sectional side view of the nuclear reactor system and steam generator system of FIG. 2A in accordance with an additional embodiment of the present technique. [Figure 3B] FIG. 3B is an enlarged isometric view of the steam generator system of FIG. 3A showing the lower tube sheet configured in accordance with an embodiment of the present technique. [Figure 4A] FIG. 2B is an enlarged cross-sectional side view of the nuclear reactor system and steam generator system of FIG. 2A in accordance with an additional embodiment of the present technique. [Figure 4B] FIG. 4B is an enlarged cross-sectional side view of the steam generator system of FIG. 4A showing a lower tube sheet assembly in accordance with an embodiment of the present technique. [Figure 5A] 5A-5D show a front view, a rear view, a cross-sectional side view, and a cross-sectional isometric view, respectively, of a portion of a nuclear reactor system configured in accordance with an embodiment of the present technique. [Figure 5B]5A-5D show a front view, a rear view, a cross-sectional side view, and a cross-sectional isometric view, respectively, of a portion of a nuclear reactor system configured in accordance with an embodiment of the present technique. [Figure 5C] 5A-5D show a front view, a rear view, a cross-sectional side view, and a cross-sectional isometric view, respectively, of a portion of a nuclear reactor system configured in accordance with an embodiment of the present technique. [Figure 5D] 5A-5D show a front view, a rear view, a cross-sectional side view, and a cross-sectional isometric view, respectively, of a portion of a nuclear reactor system configured in accordance with an embodiment of the present technique. [Figure 6A] 6A-6C are cross-sectional side views of the interface of the steam generator system of the nuclear reactor system of FIGS. 5A-5D illustrating different geometries for the exterior surface of the interface in accordance with embodiments of the present technique. [Figure 6B] 6A-6C are cross-sectional side views of the interface of the steam generator system of the nuclear reactor system of FIGS. 5A-5D illustrating different geometries for the exterior surface of the interface in accordance with embodiments of the present technique. [Figure 6C] 6A-6C are cross-sectional side views of the interface of the steam generator system of the nuclear reactor system of FIGS. 5A-5D illustrating different geometries for the exterior surface of the interface in accordance with embodiments of the present technique. [Figure 7A] 7A-7C are cross-sectional front, rear, and side views, respectively, of the reactor system of FIGS. 5A-5D including a connection portion of a steam generator system configured in accordance with additional embodiments of the present technique. [Figure 7B] 7A-7C are cross-sectional front, rear, and side views, respectively, of the reactor system of FIGS. 5A-5D including a connection portion of a steam generator system configured in accordance with additional embodiments of the present technique. [Figure 7C] 7A-7C are cross-sectional front, rear, and side views, respectively, of the reactor system of FIGS. 5A-5D including a connection portion of a steam generator system configured in accordance with additional embodiments of the present technique. DETAILED DESCRIPTION OF THE INVENTION

[0008] Aspects of the present disclosure are generally directed to a steam generator system including a tube sheet assembly, such as for use in a nuclear reactor power system and related devices and methods. More particularly, some aspects of the present disclosure are directed to a stress-relieving attachment for attaching a tube sheet to a reactor vessel in a nuclear reactor power system. In some of the embodiments described below, for example, a representative steam generator system is installed in a reactor vessel (e.g., a reactor pressure vessel shell) positioned to contain a primary coolant. The steam generator system may include a tube sheet assembly defining a plenum. The tube sheet assembly includes a tube sheet and a flexible connection portion connecting the tube sheet to the reactor vessel. The tube sheet may include a plurality of perforations fluidly coupled to the plenum. The steam generator system may further include a plurality of heat transfer tubes fluidly coupled to the perforations to receive a flow of secondary coolant. The connection portion may be more flexible than the tube sheet and reactor vessel to reduce stresses in the tube sheet and at the connection points (e.g., tube-to-tube sheet (TTS) welds) between the heat transfer tubes and the tube sheet during operation of the nuclear reactor system. For example, the connection portion may be thinner than both the tubesheet and the adjacent reactor vessel.

[0009] Thus, in some aspects of the present technology, connections may alleviate or reduce stresses (e.g., discontinuous stresses and / or fatigue) in the tubesheet and / or at associated connections (e.g., tube-to-tubesheet (TTS) welds) between the tubesheet and corresponding heat transfer tubes by acting like a flexible connection between the reactor vessel and the tubesheet. Such flexible connections can isolate mismatched deformations between the different geometries of the tubesheet (e.g., a perforated flat plate) and the reactor vessel (e.g., a cylindrical vessel) during cyclic loading. In some embodiments, the cyclic fatigue life of the tubesheet and associated TTS welds may be increased by one, two, or more orders of magnitude, increasing the life of the steam generator system.

[0010] To fully understand various embodiments of the present technology, the following description and the predetermined details are described in FIGS. 1 to 7C. In other examples, well-known structures, materials, operations, and / or systems often associated with tube sheet assemblies, tube sheets, nuclear reactor power conversion systems, heat transfer tubes, steam generators, etc. are not shown in detail or described in the following disclosure so as not to unnecessarily obscure the description of various embodiments of the present technology. However, those skilled in the art will recognize that the present technology can be implemented even without one or more of the details described herein and / or by other structures, methods, components, etc.

[0011] The terms used hereinafter should be interpreted in the broadest reasonable manner even when used with a detailed description of a predetermined example of an embodiment of the present technology. In fact, although certain terms may even be emphasized hereinafter, no terms intended to be interpreted in any restricted manner are explicitly and specifically defined as such in this section of the detailed description.

[0012] The accompanying drawings depict multiple embodiments of the present technology and are not intended to limit its scope unless explicitly indicated. The sizes of the various elements depicted are not necessarily drawn to scale, and these various elements can be enlarged to improve readability. Details of components can be abstracted in the drawings to exclude details such as the position of the components and the specific exact connections between the components when such details are unnecessary for a complete understanding of the manufacturing and use methods of the present technology. Many of the details, dimensions, angles, and other features shown in the drawings are merely illustrative of specific embodiments of the present disclosure. Therefore, other embodiments can have other details, dimensions, angles, and features without departing from the present technology. In addition, those skilled in the art will understand that further embodiments of the present technology can also be implemented even without some of the details described below.

[0013] To the extent that any document incorporated by reference herein conflicts with this disclosure, this disclosure will control. The headings provided herein are for convenience only and should not be construed as limiting the subject matter described.

[0014] I. SELECTED EMBODIMENTS OF NUCLEAR REACTOR POWER CONVERSION SYSTEMS

[0015] FIG. 1 is a partially schematic, partial cross-sectional view of a nuclear reactor system 100 configured in accordance with an embodiment of the present technique. The system 100 includes a power module 102 having a core 104 in which a controlled nuclear reaction occurs. Accordingly, the core 104 may include one or more fuel assemblies 101. The fuel assemblies 101 may include fissile and / or other suitable materials. Heat from the reaction generates steam in one or more steam generator systems 130, which direct the steam to a power conversion system 140. The power conversion system 140 generates electrical power and / or provides other useful output. A sensor system 150 is used to monitor the operation of the power module 102 and / or other system components. Data obtained from the sensor system 150 can be used in real time to control the power module 102 and / or to update the design of the power module 102 and / or other system components.

[0016] The power modules 102 include a containment vessel 110 (e.g., a radiation-shielded vessel, a radiation-shielded containment, etc.) that houses / encloses a reactor vessel 120 (e.g., a reactor pressure vessel, a reactor pressure shell, a reactor pressure containment, etc.). The reactor vessel 120 houses a reactor core 104. The containment vessel 110 may be housed in a power module bay 156. The power module bay 156 houses a cooling pool 103 filled with water and / or other suitable cooling liquid. A majority of the power modules 102 are disposed below a surface 105 of the cooling pool 103. Thus, the cooling pool 103 may act as a heat sink, for example, in the event of a system malfunction.

[0017] The volume between the reactor vessel 120 and the containment vessel 110 may be partially or completely evacuated to reduce heat transfer from the reactor vessel 120 to the surrounding environment (e.g., to the cooling pool 103). However, in other embodiments, the volume between the reactor vessel 120 and the containment vessel 110 may be at least partially filled with gas and / or liquid to increase heat transfer between the reactor vessel 120 and the containment vessel 110.

[0018] Within the reactor vessel 120, a primary coolant 107 transfers heat from the core 104 to a steam generator system 130. For example, as indicated by arrows located within the reactor vessel 120, the primary coolant 107 is heated in the core 104 and directed toward the bottom of the reactor vessel 120. The heated primary coolant 107 (e.g., water with or without additives) rises from the core 104 through the core shroud 106 and into the riser pipe 108. The hot, buoyant primary coolant 107 continues to rise through the riser pipe 108 before exiting the riser pipe 108 and descending through the steam generator 130. The steam generator system 130 includes a plurality of conduits 132 (e.g., tubes, heat transfer tubes) arranged circumferentially around the riser pipe 108, for example, in a helical pattern, as shown schematically in FIG. 1 . The descending primary coolant 107 transfers heat to the secondary coolant (e.g., water) in conduit 132 and descends to the bottom of reactor vessel 120, where the cycle begins again. The cycle can be driven by changes in buoyancy of the primary coolant 107, thereby reducing or eliminating the need for pumps to move the primary coolant 107.

[0019] The steam generator system 130 may include a lower header assembly 131 (e.g., a lower plenum assembly, a lower tube sheet assembly, a feedwater header assembly, a first header assembly, a first tube sheet assembly, etc.) through which incoming secondary coolant enters steam generator conduits 132. The secondary coolant rises through the conduits 132, is converted to steam (e.g., water vapor), and is collected in an upper header assembly 133 (e.g., an upper plenum assembly, an upper tube sheet assembly, a steam header assembly, a second header assembly, a second tube sheet assembly, etc.). The steam exits the upper header assembly 133 and is directed to the power conversion system 140.

[0020] Power conversion system 140 may include one or more steam valves 142 that regulate the passage of high-pressure, high-temperature steam from steam generator system 130 to steam turbine 143. Steam turbine 143 converts the thermal energy of the steam into electricity via generator 144. Low-pressure steam exiting steam turbine 143 is condensed in condenser 145 and then directed (e.g., via pump 146) to one or more feedwater valves 141. Feedwater valve 141 controls the rate at which feedwater re-enters steam generator system 130 via lower header assembly 131.

[0021] The power module 102 includes multiple control systems and associated sensors. For example, the power module 102 may include a hollow cylindrical reflector 109. The hollow cylindrical reflector 109 returns neutrons to the reactor core 104 to drive the nuclear reaction in the reactor core 101. Control rods 113 are used to regulate the nuclear reaction and are driven via fuel rod drivers 115. The pressure within the reactor vessel 120 may be controlled by controlling the pressure in a pressurized volume 119 located above the pressurizer plate 113 (which may also direct the primary coolant 107 downward through the steam generator system 130) via the pressurizer plate 113. In some embodiments, an upper header assembly 133 may be at least partially integrated into the pressurizer plate 117.

[0022] Sensor system 150 may include one or more sensors 151 positioned at various locations within power module 102 and / or elsewhere to, for example, identify operating parameter values ​​and / or changes in parameter values. Data collected by sensor system 150 may then be used to control the operation of system 100 and / or to effect design changes for system 100. For sensors positioned within containment vessel 110, sensor links 152 route data from the sensors to flange 153 (where sensor link 152 exits containment vessel 110) and route the data to sensor junction box 154. From there, the sensor data is routed via data bus 155 to one or more controllers and / or other data systems.

[0023] II. SELECTED EMBODIMENTS OF STEAM GENERATOR SYSTEMS AND TUBE SHEET ASSEMBLY

[0024] 2A through 5 illustrate various steam generator systems or portions thereof configured in accordance with embodiments of the present technique that may be used in nuclear reactor system 100 and / or other nuclear reactor systems. For example, various steam generator systems may be used in addition to or instead of steam generator system 130 detailed above with reference to FIG. 1 and may function in a similar or identical manner. In some embodiments, the steam generator system may include some features that are at least generally similar in structure and function to, or identical in structure and function to, the steam generator systems disclosed in (i) U.S. Pat. No. 9,997,262, filed April 24, 2014, entitled "Integral Reactor Pressure Vessel Tube Sheet," and / or (ii) U.S. Pat. No. 10,685,752, filed February 10, 2015, entitled "Steam Generator with Inclined Tube Plate," each of which is incorporated herein by reference in its entirety.

[0025] 2A is a cross-sectional side view of a nuclear reactor system 200 (e.g., a nuclear power generation system, a nuclear power conversion system, a nuclear reactor steam generation system, etc.) including a steam generator system 230 configured in accordance with an embodiment of the present technique. The nuclear reactor system 200 may include a reactor vessel 220 configured to house (i) a reactor core (not shown in FIG. 2A ) that generates heat, (ii) a primary coolant that absorbs heat from the nuclear reactor, and (iii) a riser tube 208. The reactor vessel 220 may have a cylindrical shape. In the illustrated embodiment, the steam generator system 230 includes a plurality of heat transfer tubes 232 (e.g., conduits) disposed within the reactor vessel 220 and arranged circumferentially around the riser tube 208. The tubes 232 extend helically around the riser tube 208. Individual ones of the tubes 232 have a lower portion that is fluidly coupled to a lower tube sheet assembly 231 (e.g., a lower header assembly) and an upper portion that is fluidly coupled to an upper tube sheet assembly 233 (e.g., an upper header assembly). The lower tube sheet assembly 231 and the upper tube sheet assembly 233 may be similar or identical in structure and / or function to the lower header assembly 131 and the upper header assembly, respectively, described above with reference to FIG.

[0026] In some embodiments, the steam generator system 230 includes a plurality (e.g., four) of lower tube sheet assemblies 231 and / or a plurality (e.g., four) of upper tube sheet assemblies 233 arranged circumferentially around the reactor vessel 220. Pairs of the lower and upper tube sheet assemblies 231, 233 may be fluidly coupled to a set of tubes 232 to define individual steam generator circuits. The lower and upper tube sheet assemblies 231, 233 may be coupled to or integral with the reactor vessel 220 and arranged to provide a fluid flow path from the tubes 232 to / from the reactor vessel 220 to / from an external power conversion system (e.g., power conversion system 140 in FIG. 1 ). In some embodiments, the lower and upper tube sheet assemblies 231, 233 are completely enclosed within a containment vessel (e.g., containment vessel 110 in FIG. 1 ) that surrounds the reactor vessel 220.

[0027] During operation, the primary coolant in the reactor vessel 220 is heated and flows upward through the riser pipes 208, passing through the tubes 232, and then downward through the tubes 232 outside the riser pipes 208. The tubes 232 receive a secondary coolant (e.g., water) through the lower tube sheet assembly 231. The secondary coolant rises through the tubes 232, and heat is transferred from the primary coolant to the secondary coolant, which becomes superheated steam (e.g., steam). The secondary coolant in the steam generator system 230 may be separated from the primary coolant in the reactor vessel 220, and they are not allowed to mix or come into direct contact with each other. The vaporized secondary coolant exits the tubes 232 and enters the upper tube sheet assembly 233 for transport to the power conversion system. After the heat from the secondary coolant is utilized by the power conversion system, the secondary coolant may be returned to the steam generator system 230 through the lower tube sheet assembly 231.

[0028] The multiple lower tube sheet assemblies 231 may be identical, and each may include a body 234 (e.g., a wall, body portion, wall portion, etc.) integrally formed with or attached to the reactor vessel 220 to define a plenum 235. The body 234 may include a tube sheet 236 (e.g., a perforated plate), and / or the tube sheet 236 may be a separate component attached to the body 234. Lower portions of the tubes 232 may be coupled (e.g., welded, fastened) to the tube sheet 236, which is positioned to route secondary coolant from the plenum 235 to the tubes 232. In the illustrated embodiment, the tube sheet 236 is positioned within the annular region between the reactor vessel 220 and the riser pipe 208 and is oriented in a horizontal or radial position. That is, the tube sheet 236 may extend along an axis X that is perpendicular to the longitudinal axis Y of the reactor vessel 220. Body 234 may further include / define inlet ports 237 (e.g., supply nozzles) that may be connected to supply pipes that receive secondary coolant. Inlet ports 237 are positioned to direct secondary coolant from the supply pipes into plenum 235. In some embodiments, lower tube sheet assembly 231 further includes a removable cover plate 238 that may be coupled (e.g., bolted) to body 234 to enclose plenum 235. Removable cover plate 238 may be removed from and / or installed on body 234 during one or more operations, such as maintenance, inspection, and / or installation.

[0029] 2B is an enlarged cross-sectional side view of one of the upper tube sheet assemblies 233 configured in accordance with an embodiment of the present technique. Referring to FIGS. 2A and 2B, the upper tube sheet assemblies 233 may be identical and may include some features generally similar or identical to those of the lower tube sheet assembly 231. For example, each upper tube sheet assembly 233 may include a body 244 integrally formed with or attached to the reactor vessel 220 to define or bound a plenum 245. The body 244 may define or include a tube sheet 246 (e.g., a perforated plate), and / or the tube sheet 246 may be a separate component attached to the body 244. In some embodiments, the tube sheet 246 comprises a portion of the pressurizer plate 217 of the nuclear reactor system 200. Upper portions of the tubes 232 may be coupled (e.g., welded, fastened) to the tube sheet 246, which is positioned to route secondary coolant from the tubes 232 to the plenum 245. In the illustrated embodiment, the tube sheet 246 is oriented in a horizontal or radial position. That is, the tube sheet 246 may extend along an X-axis that is perpendicular to the longitudinal axis Y of the reactor vessel 220. The body 244 may further include / define outlet ports 247 (e.g., steam nozzles) that may be connected to steam pipes 241 ( FIG. 2B ) that receive secondary coolant. The outlet ports 247 are positioned to direct secondary coolant from the plenum 245 to the steam pipes. In some embodiments, the upper tube sheet assembly 233 further includes a removable cover plate 248 that may be coupled (e.g., bolted) to the body 244 to enclose the plenum 245. The removable cover plate 248 may be removed from and / or installed on the body 244 during one or more operations, such as maintenance, inspection, and / or installation. Referring to FIG. 2B , the tube sheet 236 may be a generally flat plate that includes a plurality of perforations 239 (e.g., through-holes) arranged in rows. Perforations 239 may extend through tube sheet 236 and be oriented parallel to axis Y (FIG. 2A). Perforations 239 may be coupled (e.g., via welding) to corresponding ones in tubes 232.

[0030] In some embodiments, the lower tube sheet assembly 231 and / or the upper tube sheet assembly 233 may have different configurations. For example, FIG. 3A is an enlarged cross-sectional side view of the reactor system 200 and steam generator system 230 configured in accordance with additional embodiments of the present technique. In the illustrated embodiment, the body 234 is attached to or integrally formed with the reactor vessel 220 and positioned generally radially outward of the reactor vessel 220. The tube sheet 236 is positioned at and / or adjacent to a wall of the reactor vessel 220 (e.g., substantially outside the annular region between the reactor vessel 220 and the riser pipe 208) and is oriented in a vertical position. That is, the tube sheet 236 may extend generally parallel to the longitudinal axis Y of the reactor vessel 220.

[0031] 3B is an enlarged isometric view of the nuclear reactor system 200 illustrating one of the lower tube sheet assemblies 231 of FIG. 3A in accordance with an embodiment of the present technique. In the illustrated embodiment, the tube sheet 236 is a generally circular, flat plate including a plurality of perforations 339 (e.g., through-holes) arranged in rows. The perforations 339 may extend through the tube sheet 236 and be oriented parallel to the axis X. The perforations 339 in individual ones of the rows may be coupled to corresponding ones of the tubes 232 in a vertical group of the tubes 232. For clarity, only a portion of the tubes 232 are shown in FIG. 3B.

[0032] FIG. 4A is an enlarged cross-sectional side view of a nuclear reactor system 200 and a steam generator system 230 configured in accordance with an additional embodiment of the present technique. FIG. 4B is an enlarged cross-sectional side view of the nuclear reactor system 200 showing one of the lower tube sheet assemblies 231 of FIG. 4A in accordance with an embodiment of the present technique. Referring to FIGS. 4A and 4B, in the illustrated embodiment, a body 234 is attached to or integrally formed with the reactor vessel 220 and is disposed partially within and partially outside the reactor vessel 220. A tube sheet 236 similarly extends from within the reactor vessel 220 to the outside of the reactor vessel 220 and is angled (e.g., tilted) relative to the wall of the reactor vessel 220. That is, the tube sheet 236 may extend at a non-zero angle relative to the longitudinal axis Y and the orthogonal axis X of the reactor vessel 220. In some embodiments, the tube sheet 236 may be angled at less than about 60°, about 10° to 50°, about 15° to 45°, about 20° to 40°, about 25° to 35°, and / or about 30° relative to the longitudinal axis Y of the wall of the furnace vessel 60. As best seen in FIG. 3B , the tube sheet 236 may be a generally circular flat plate containing a plurality of perforations 439 (e.g., through holes). The perforations 439 extend through the tube sheet 236 and are angled (e.g., oblique) relative to the axes X, Y. The perforations 339 may be coupled to corresponding ones of the plurality of tubes 232.

[0033] 2A-4B , the tubesheet 236 of the lower tubesheet assembly 231 and the tubesheet 246 of the upper tubesheet assembly 233 may be perforated flat plates integrally attached to or directly affixed to the reactor vessel 220, which may have a cylindrical shape. Large stresses may develop locally at the tubesheets 236, 246 and / or at the connections between the tubes 232 and the tubesheets 236, 246 (e.g., tube-to-tubesheet (TTS) welds) due to incompatible movement of the steam generator system 230 and the reactor vessel 220 under pressure and thermal loads caused by the different geometries of the steam generator system 230 and the reactor vessel 220. That is, the reactor vessel 220 may expand / contract at different rates than the tubesheets 236, 246 under thermal and pressure loads due to the different geometries of these components. This may lead to incompatible deformation at the interfaces between the tubesheets 236, 246 and the reactor vessel 220. This can cause discontinuous stresses and fatigue during cyclic loading in the tubesheets 236, 246 and / or the connections (e.g., tube-to-tubesheet (TTS) welds) between the tubes 232 and the tubesheets 236, 246. For example, when the reactor system 200 undergoes transient conditions, including start-up and shutdown, the stresses in the tubesheets 236, 246 can become cyclical, which can lead to fatigue and premature retirement of the steam generator system 230.

[0034] In some aspects of the present technology, a tubesheet assembly (e.g., a header assembly) constructed in accordance with the present technology may relieve or reduce stresses in the tubesheet and associated TTS welds by introducing flexible connections between the reactor vessel and the tubesheet. Such flexible connections can isolate incompatible deformations between the different geometries of the tubesheet and the reactor vessel. For example, in some embodiments, the tubesheet assembly may include a flexible section or portion between the reactor vessel and the tubesheet that is thinner than both the reactor vessel and the tubesheet. This may provide stress relief for the tubesheet by being more flexible than the components it connects (e.g., the tubesheet and the reactor vessel).

[0035] For example, Figures 5A-5D respectively illustrate a front view, a rear view, a cross-sectional side view, and a cross-sectional isometric view of a portion of a nuclear reactor system configured in accordance with an embodiment of the present technique. Nuclear reactor system 500 may include some features generally similar to or identical to those of nuclear reactor systems 100 and / or 200 described above with reference to Figures 1-4B. For example, with reference to Figures 5A-5D, nuclear reactor system 500 includes a steam generator system having a tube sheet assembly 550 integrally formed with a reactor vessel 520. Specifically, Figure 5A is a front view of tube sheet assembly 550 from within reactor vessel 520 (e.g., generally facing in a direction toward the exterior of reactor vessel 520), and Figure 5B is a rear view of tube sheet assembly 550 from outside reactor vessel 520 (e.g., generally facing in a direction toward the interior of reactor vessel 520). Reactor vessel 520 may have a cylindrical shape. In other embodiments, the tubesheet assembly 550 may be a separate component that is coupled to the reactor vessel (eg, via weld bolts, fasteners, etc.).

[0036] In the illustrated embodiment, the tubesheet assembly 550 includes a body 534 that (at least partially) defines or bounds a plenum 535 (hidden in FIGS. 5A and 5B ). The body 534 may further define a tubesheet 536 (e.g., a perforated plate), and / or the tubesheet 536 may be a separate component that is attached to the body 534 and the furnace vessel 520. In the illustrated embodiment, the tubesheet 536 is angled (e.g., tilted) at an angle A ( FIG. 5C ) relative to the longitudinal axis Y ( FIG. 5C ) of the furnace vessel 520. Angle A may be less than about 60°, about 10° to 50°, about 15° to 45°, about 20° to 40°, about 25° to 35°, and / or about 30°. As best seen in FIGS. 5A and 5B , the tubesheet 536 may be a generally circular, flat plate that includes a plurality of perforations 539 (e.g., through-holes). The perforations 539 extend through the tube sheet 236 and are angled (e.g., tilted) relative to the axes X, Y. In some embodiments, the perforations 539 are arranged in multiple rows that may decrease in number downward along the longitudinal axis Y. The perforations 539 may be coupled (e.g., welded) to corresponding ones of the heat transfer tubes of the steam generator system.

[0037] Body 534 may further include / define ports 537 (e.g., nozzles) fluidly coupled to plenum 535. In some embodiments, tubesheet assembly 550 is a lower tubesheet assembly (e.g., a feed assembly) configured to (i) receive secondary coolant through ports 537 and (ii) direct the secondary coolant through plenum 535, out perforations 539, and into corresponding heat transfer tubes coupled to tubesheet 536 (e.g., from lower portions of the heat transfer tubes). In other embodiments, tubesheet assembly 550 is an upper tubesheet assembly (e.g., a steam assembly) configured to (i) receive secondary coolant in steam form through perforations 539 from heat transfer tubes coupled to tubesheet 536 (e.g., from upper portions of the heat transfer tubes), and (ii) direct the secondary coolant in steam form through plenum 535 to ports 537 for exit to the power conversion system.

[0038] 5C, tubesheet assembly 550 may further include a removable cover plate 538, which may be coupled to body 534, for example, via bolts 559. When attached to body 534, cover plate 538 may enclose plenum 535. Cover plate 538 may be removed from and / or installed on body 534 during one or more operations, such as maintenance, inspection, and / or installation. For purposes of clarity, cover plate 538 is shown removed in FIGS. 5A, 5B, and 5D.

[0039] 5A-5D, the tube sheet 536 includes an inner surface 551 (hidden in FIG. 5B) positioned to face the interior of the reactor vessel 520 and an outer surface 552 (hidden in FIG. 5A) opposite the inner surface 551 and positioned to face the plenum 535 and the cover plate 538. Perforations 539 may penetrate the tube sheet 536 completely from the inner surface 551 to the outer surface 552. Referring to FIGS. 5B-5D, the tube sheet assembly 550 further includes a groove 553 extending circumferentially around the tube sheet 536. The groove 553 defines a connection portion 554 (which may be referred to as a connection region, flexible portion, stress relief portion, thinned portion, weakened portion, etc.) between the tube sheet 536 and an adjacent portion of the reactor vessel 520 and / or body 534. Thus, the connection portion 554 may have a thickness T1 (FIG. 5C) that is less than the thickness T2 (FIG. 5C) of the tube sheet 536. In some embodiments, thickness T2 may be about 2 to 6 times, about 2 times, about 3 times, and / or about 4 times greater than thickness T1. Tube sheet 536 may be integral with connection portion 554, body 534, and / or furnace vessel 520.

[0040] In the illustrated embodiment, the groove 553 and the connecting portion 554 extend completely around the tube sheet 536 and each have a circular shape with a constant width W ( FIG. 5C ). That is, the connecting portion 554 may be a thin annular ring around the tube sheet 536. Furthermore, the groove 553 extends from the outer surface 552 of the tube sheet 536 toward the inner surface 551 of the tube sheet 536 such that the connecting portion 554 is disposed adjacent to the inner surface 551 of the tube sheet 536. Specifically, with reference to FIGS. 5C and 5D , the connecting portion 554 may include an inner surface 555 disposed to face the interior of the furnace vessel 520 and an outer surface 556 opposite the inner surface 555, disposed within the groove 553, facing the plenum 535. The inner surface 555 of the connecting portion 554 may be flush with the inner surface 551 of the tube sheet 536, while the outer surface 556 of the connecting portion 554 may be offset from the outer surface 552 of the tube sheet 536. In other embodiments, the grooves 553 may extend only partially around the tube sheet 536, may have other shapes (e.g., as shown in Figures 7A-7C and described in more detail with reference to Figures 7A-7C), and / or may alternatively or additionally extend from the inner surface 551 (e.g., as shown in Figures 7A-7C and described in more detail with reference to Figures 7A-7C).

[0041] In the illustrated embodiment, the inner and outer surfaces 555, 556 of the connecting portion 554 are each planar / flat. In other embodiments, the inner and / or outer surfaces 555, 556 may have different geometries. For example, FIGS. 6A-6C are cross-sectional side views of the connecting portion 554 illustrating different geometries for the outer surface 556 in accordance with embodiments of the present technology. As shown in FIGS. 6A-6C, respectively, the outer surface 556 may have a curved spherical shape, a curved cylindrical shape, and / or an omega shape. In other embodiments, the inner surface 555 may have a similar shape, and / or the inner surface 555 and / or outer surface 556 may have other shapes (e.g., polygonal, irregular, etc.).

[0042] 5A-5D , the connection portion 554 may be thinner than the adjacent components (e.g., tube sheet 536, body 534, and reactor vessel 520) to which it is connected, and therefore may be more flexible (e.g., less rigid) than these adjacent components. In some embodiments, the connection portion 554 may alternatively or additionally be formed from a material that is more flexible than the reactor vessel 520 and tube sheet 536. Thus, in some aspects of the present technology, the connection portion 554 may act as a flexible connection between the reactor vessel 520 and the tube sheet 536, thereby mitigating or reducing stresses (e.g., discontinuous stresses and / or fatigue) at the tube sheet 536 and / or at associated connections (e.g., tube-to-tube sheet (TTS) welds) between the tube sheet 536 and corresponding heat transfer tubes. Such flexible connections may isolate incompatible deformations between the different geometries of the tube sheet 536 (e.g., a perforated flat plate) and the reactor vessel 520 (e.g., a cylindrical vessel) during cyclic loading. In some embodiments, the cyclic fatigue life of the tubesheet 536 and associated TTS welds may be increased by an order of magnitude, two orders of magnitude, or more, increasing the life of the steam generator system 530 .

[0043] In some embodiments, each individual one of the plurality of perforations 539 may receive a corresponding heat transfer tube therein, and the heat transfer tube may be welded (e.g., via a TTS weld) or otherwise connected to the tubesheet 536 at and / or near the outer surface 552 of the tubesheet 536. Thus, the connection between the heat transfer tube and the tubesheet 536 may be located adjacent the groove 553 opposite a connection portion 554 that extends from near the inner surface 551 of the tubesheet 536. The connection portion 554 may extend from the outer surface 552 of the tubesheet 536 adjacent to the groove 553 opposite the connection portion 554. 552 On or outside 552 554, the tube sheet 536 may easily flex near the outer surface 552. Thus, in some aspects of the present technology, spacing the connections between the heat transfer tubes and the tube sheet 536 away from the connection portions 554 in this manner can further reduce stresses at the connections during operation of the reactor system 500.

[0044] In some embodiments, the connecting portion 554 can be manufactured by milling the groove 553 through a tool that is inserted into the plenum 535 with the cover plate 538 removed. In some aspects of the present technology, the groove 553 can be formed circular and have a consistent width and depth, thereby reducing the complexity of the manufacturing process used to form the groove 553.

[0045] As mentioned above, tube sheet assemblies according to the present technique can have other configurations of grooves extending around the tube sheet that provide a flexible connection between the tube sheet and the adjacent reactor vessel. Figures 7A-7C are, for example, cross-sectional front, rear, and side views, respectively, of a nuclear reactor system 500 including a connecting portion 754 according to further embodiments of the present technique. With reference to Figures 7A-7C, with the exception of connecting portion 754, the components of reactor system 500 may be similar or identical to the components shown and described in detail with reference to Figures 5A-5D and are referred to by the same reference numerals.

[0046] In the illustrated embodiment, the tubesheet assembly 550 includes an inner groove 757 and an outer groove 758 extending circumferentially around the tubesheet 536 to define a connecting portion 754 between the tubesheet 536 and an adjacent portion of the furnace vessel 520 and / or body 534. Accordingly, the connecting portion 754 may have a thickness T1 (FIG. 7C) that is less than the thickness T2 (FIG. 7C) of the tubesheet 536. In some embodiments, the thickness T2 may be about 2 to 6 times, about 2 times, about 3 times, and / or about 4 times greater than the thickness T1. The tubesheet 536 may be integral with the connecting portion 754, the body 534, and / or the furnace vessel 520.

[0047] In the illustrated embodiment, the inner and outer grooves 757, 758 and the connecting portion 754 extend completely around the tube sheet 536, each having a diamond-like or shield-like shape with a variable width W ( FIG. 7C ) around the tube sheet 536. In some embodiments, the width W may be selected to maintain a minimum clearance between the connecting portion 754 and the perforations 539. Furthermore, the inner groove 757 extends from the inner surface 551 of the tube sheet 536 toward the outer surface 552 of the tube sheet, and the outer groove 758 extends from the outer surface 552 of the tube sheet 536 toward the inner surface 551 of the tube sheet 536, such that the connecting portion 754 is positioned adjacent to a middle portion of the tube sheet 536. Specifically, the connecting portion 754 may include (i) an inner surface 755 disposed within the inner groove 757 facing the interior of the reactor vessel 520, and (ii) an outer surface 756 opposite the inner surface 755 disposed within the outer groove 758 facing the plenum 535. The inner surface 755 of the connecting portion 754 may be offset (e.g., spaced) from the outer surface 552 of the tube sheet 536 , and the outer surface 756 of the connecting portion 754 may likewise be offset from the outer surface 552 of the tube sheet 536 .

[0048] Thus, in some aspects of the present technology, the connection portion 754 may be thinner than the adjacent components to which it is connected (e.g., the tube sheet 536, the body 534, and the reactor vessel 520), and therefore may be more flexible (e.g., less rigid) than these adjacent components. Thus, in some aspects of the present technology, the connection portion 754 may act as a flexible connection between the reactor vessel 520 and the tube sheet 536, thereby relieving or reducing stresses (e.g., discontinuity stresses and / or fatigue) at the tube sheet 536 and / or at associated connections (e.g., tube-to-tube sheet (TTS) welds) between the tube sheet 536 and corresponding heat transfer tubes.

[0049] 5A-7C depict a tubesheet assembly having a tubesheet 536 that is angled (e.g., tilted) relative to the longitudinal axis L of the furnace vessel 520, the flexible connections of the present technology (e.g., connection 554 and / or connection 754) may be used with tubesheets having any orientation / configuration described herein and / or in any configuration in which the tubesheet is integrally attached to the furnace vessel. For example, with reference to FIG. 2A, flexible connections may be formed between any or all of the horizontally oriented tubesheets 236 of the lower tubesheet assembly 231 and the furnace vessel 220, and / or between the horizontally oriented tubesheets 236 and the main body 234 of the tubesheets 236. 2A and 2B, flexible connections may be formed in the pressurizer plate 217 between any or all of the tube sheets 246 of the upper tube sheet assembly 233, between the tube sheets 246 and the furnace vessel 220, and / or between the tube sheets 246 and the body 244 of the tube sheets 246. Similarly, with reference to Figures 3A and 3B, flexible connections may be formed between any or all of the vertically oriented tube sheets 236 of the lower tube sheet assembly 231 and the furnace vessel 220, and / or between the vertically oriented tube sheets 236 and the body 234 of the tube sheets 236.

[0050] III. Additional Examples

[0051] The following examples illustrate some embodiments of the present technology. [Example 1] A steam generator system for use in a nuclear reactor system including a reactor vessel arranged to contain a primary coolant, a tubesheet assembly coupled to the reactor vessel to form at least a portion of a plenum; a plurality of heat transfer tubes configured to receive a flow of secondary coolant; Including, The tubesheet assembly is a tube sheet including a plurality of perforations fluidly coupled to the plenum; an at least partial connection between the tube sheet and the reactor vessel, the connection being more flexible than the tube sheet and the reactor vessel; Including, A steam generator system in which individual ones of the heat transfer tubes are coupled to corresponding ones of the plurality of perforations. [Example 2] The steam generator system of Example 1, wherein the tubesheet is a flat plate and the tubesheet assembly includes a groove extending circumferentially around the tubesheet to define a connection portion. [Example 3] The steam generator system of Example 2, wherein the tube sheet includes an inner surface positioned to face the interior of the reactor vessel and an outer surface positioned to face the plenum, and the grooves extend partially from the outer surface toward the inner surface. [Example 4] The steam generator system of Example 2 or Example 3, wherein the flat plate has a circular shape and the groove has a circular shape with a generally constant width and depth. [Example 5] The steam generator system of Example 2 or Example 3, wherein the groove has a width that varies circumferentially. [Example 6] A steam generator system according to any one of Examples 1 to 5, wherein the tube sheet assembly is integrally formed with the reactor vessel. [Example 7] The steam generator system of any one of Examples 1 to 6, wherein the reactor vessel extends along a longitudinal axis and the tube sheets are arranged generally parallel to the longitudinal axis. [Example 8] The steam generator system of any one of Examples 1 to 6, wherein the reactor vessel extends along a vertical axis and the tube sheets are inclined at an angle of approximately 15° to 45° relative to the vertical axis. [Example 9] The steam generator of any one of Examples 1 to 6, wherein the reactor vessel extends along a longitudinal axis and the tube sheets are arranged generally perpendicular to the longitudinal axis. [Example 10] A steam generator system according to any one of Examples 1 to 9, wherein the tube sheet is a flat plate having an inner surface arranged to face the inside of the reactor vessel and an outer surface arranged to face the plenum, and the tube sheet assembly includes a first groove extending circumferentially around the tube sheet from the inner surface partially toward the outer surface, and a second groove extending circumferentially around the tube sheet from the outer surface partially toward the inner surface, and the first groove and the second groove define a connecting portion. [Example 11] A steam generator system according to any one of Examples 1 to 10, wherein the tube sheet has a first thickness and the connection portion has a second thickness that is smaller than the first thickness. [Example 12] The steam generator system of Example 11, wherein the first thickness is less than half the second thickness. [Example 13] A steam generator system according to any one of Examples 1 to 12, wherein the tube sheet assembly further includes an inlet port fluidly coupled to the plenum, and the tube sheet assembly is arranged to receive a secondary coolant in liquid form through the inlet port and route the secondary coolant in liquid form through the plenum, into the perforations and into the heat transfer tubes. [Example 14] A steam generator system according to any one of Examples 1 to 12, wherein the tube sheet assembly further includes an outlet port fluidly coupled to the plenum, and the tube sheet assembly is arranged to receive secondary coolant in the form of steam from the heat transfer tubes and route the secondary coolant in the form of steam through the perforations into the plenum and into the outlet port. [Example 15] A tube sheet assembly for use in a nuclear reactor system including a reactor vessel, a body that bounds at least a portion of the plenum; a tube sheet including a plurality of perforations fluidly coupled to the plenum, the tube sheet assembly being coupled to the body and the reactor vessel; At least a partial connection between the tube sheet and the reactor vessel, the connection being more flexible than the tube sheet and the reactor vessel; a tube sheet assembly including: [Example 16] A tube sheet assembly of Example 15, wherein the tube sheet is a circular flat plate having an inner surface arranged to face the inside of the furnace vessel and an outer surface arranged to face the plenum, and the tube sheet assembly includes a circular groove extending circumferentially around the tube sheet to define a connection portion, the circular groove extending partially from the outer surface toward the inner surface. [Example 17] A tube sheet assembly of Example 15 or Example 16, wherein the tube sheet is a circular flat plate having an inner surface arranged to face the inside of the furnace vessel and an outer surface arranged to face the plenum, the tube sheet has a first thickness in one direction between the inner surface and the outer surface, and the connecting portion has a second thickness in the same direction between the inner surface and the outer surface that is smaller than the first thickness. [Example 18] The tube sheet assembly of any one of Examples 15 to 17, wherein the furnace vessel extends along a vertical axis and the tube sheet is inclined at an angle of approximately 30° relative to the vertical axis. [Example 19] A nuclear reactor system, a reactor vessel arranged to contain a reactor core and a primary coolant, the primary coolant arranged to absorb heat from a nuclear reaction in the reactor core; Steam generator assembly and Including, The steam generator assembly comprises: a first tube sheet assembly including a first tube sheet, the first tube sheet coupled to the reactor vessel and including a plurality of first perforations, the first tube sheet assembly including a flexible connection portion disposed between the first tube sheet and the reactor vessel, the flexible connection portion including an annular ring around the first tube sheet having a thickness less than a thickness of the first tube sheet; a second tube sheet assembly including a second tube sheet, the second tube sheet being coupled to the reactor vessel and including a plurality of second perforations; a plurality of heat transfer tubes configured to receive a secondary coolant; Including, 1. A nuclear reactor system, wherein the secondary coolant is configured to absorb heat from the primary coolant through heat transfer tubes, each of the heat transfer tubes having a first portion fluidly coupled to a corresponding one of the first perforations in the first tube sheet and a second portion fluidly coupled to a corresponding one of the second perforations in the second tube sheet. [Example 20] The reactor system of Example 19, wherein the first tube sheet assembly is arranged to receive a secondary coolant in liquid form and route the secondary coolant in liquid form to the heat transfer tubes through the first perforations, the reactor vessel extends along a vertical axis, and the first tube sheet is inclined at an angle of approximately 15° to 45° relative to the vertical axis.

[0052] IV. Summary

[0053] All numerical values ​​herein are assumed to be modified by the term about, whether explicitly stated or not. The term about, in the context of numerical values, generally refers to a range of numbers that one of ordinary skill in the art would consider equal to the stated value (e.g., having the same function and / or result). For example, the term about may refer to the stated value plus or minus 10 percent. For example, use of the term about 100 may refer to a range of 90 to 110. Where the context requires otherwise, and / or where relative terms are used with reference to something that does not include or relate to numerical values, the terms are to be given their ordinary meaning to those of ordinary skill in the art.

[0054] The above detailed description of embodiments of the present technology is not intended to be exhaustive or to limit the technology to the precise form disclosed above. While specific embodiments and examples of the present technology have been described above for illustrative purposes, those skilled in the art will recognize that various equivalent modifications are possible within the scope of the present technology. For example, while steps may be presented in a given order, in other embodiments, the steps may be performed in a different order. Various embodiments described herein may be combined to provide further embodiments.

[0055] It will be appreciated from the foregoing that, although specific embodiments of the present technology have been described herein for illustrative purposes, well-known structures and functions have not been shown or described in detail to avoid unnecessarily obscuring the description of the embodiments of the present technology. Where the context allows, singular or plural terms may include plural or singular terms, respectively.

[0056] As used herein, "and / or" in "A and / or B" refers to A alone, B alone, and A and B. Additionally, the terms "comprises" and "comprises" are used throughout to mean the inclusion of at least the recited features, and do not exclude any multiple of additional types of the same features and / or other features. It should also be understood that, although specific embodiments have been described herein for illustrative purposes, various modifications may be made without departing from the present technology. Furthermore, while advantages associated with some embodiments of the present technology have been described in the context of these embodiments, other embodiments may also exhibit such advantages, and not all embodiments necessarily indicate that such advantages fall within the scope of the present technology. Thus, the present disclosure and related technology may encompass other embodiments not explicitly shown or described herein.

Claims

1. A steam generator system for use in a nuclear reactor system including a reactor vessel extending along a longitudinal axis and positioned to contain a primary coolant, comprising: a tubesheet assembly coupled to the reactor vessel to form at least a portion of a plenum; a plurality of heat transfer tubes configured to receive a flow of secondary coolant; Including, The tube sheet assembly comprises: a tube sheet including a plurality of perforations fluidly coupled to the plenum; an at least partial connection between the tube sheet and the reactor vessel, the connection being more flexible than the tube sheet and the reactor vessel; Including, the connecting portion includes a flat portion offset parallel to one surface of the tube sheet; the one surface is inclined relative to the longitudinal axis; A steam generator system wherein individual ones of the heat transfer tubes are coupled to corresponding ones of the plurality of perforations.

2. 2. The steam generator system of claim 1, wherein said tube sheet is a flat plate and said tube sheet assembly includes a groove extending circumferentially around said tube sheet to define said connection portion.

3. 3. The steam generator system of claim 2, wherein the tube sheet includes an inner surface disposed facing the interior of the reactor vessel and an outer surface disposed facing the plenum, and the grooves extend partially from the outer surface toward the inner surface.

4. The steam generator system of claim 2 , wherein the flat plate has a circular shape and the groove has a circular shape with a constant width and depth.

5. The steam generator system of claim 2 wherein said groove has a width that varies circumferentially.

6. The steam generator system of claim 1 , wherein the tube sheet assembly is integrally formed with the reactor vessel.

7. 6. The steam generator system of claim 1, wherein the reactor vessel has a tube sheet inclined at an angle of 15 degrees to 45 degrees relative to the longitudinal axis.

8. 6. The steam generator system of claim 1, wherein the tube sheet is a flat plate including an inner surface disposed facing the inside of the reactor vessel and an outer surface disposed facing the plenum, and the tube sheet assembly includes a first groove extending circumferentially around the tube sheet from the inner surface partially toward the outer surface, and a second groove extending circumferentially around the tube sheet from the outer surface partially toward the inner surface, the first groove and the second groove defining the connecting portion.

9. 6. The steam generator system of claim 1, wherein the tube sheet has a first thickness and the connecting portion has a second thickness that is less than the first thickness.

10. The steam generator system of claim 9 , wherein the second thickness is less than half the first thickness.

11. 6. The steam generator system of claim 1, wherein the tube sheet assembly further includes an inlet port fluidly coupled to the plenum, the tube sheet assembly being arranged to receive the secondary coolant in liquid form through the inlet port and route the secondary coolant in liquid form through the plenum, into the perforations and into the heat transfer tubes.

12. 6. The steam generator system of claim 1, wherein the tube sheet assembly further includes an outlet port fluidly coupled to the plenum, the tube sheet assembly being arranged to receive the secondary coolant in the form of steam from the heat transfer tubes and route the secondary coolant in the form of steam through the perforations into the plenum and into the outlet port.

13. A tube sheet assembly for use in a nuclear reactor system including a reactor vessel extending along a longitudinal axis, comprising: a body that bounds at least a portion of the plenum; a tube sheet including a plurality of perforations fluidly coupled to the plenum, the tube sheet assembly being coupled to the body and the reactor vessel; an at least partial connection between the tube sheet and the reactor vessel, the connection being more flexible than the tube sheet and the reactor vessel; Including, the connecting portion includes a flat portion offset parallel to one surface of the tube sheet; the one surface is inclined relative to the longitudinal axis.

14. 14. The tubesheet assembly of claim 13, wherein the tubesheet is a circular flat plate having an inner surface disposed facing the interior of the furnace vessel and an outer surface disposed facing the plenum, the tubesheet assembly including a circular groove extending circumferentially around the tubesheet to define the connection portion, the circular groove extending from the outer surface partially toward the inner surface.

15. 14. The tubesheet assembly of claim 13, wherein the tubesheet is a circular flat plate having an inner surface disposed facing the interior of the furnace vessel and an outer surface disposed facing the plenum, the tubesheet having a first thickness in one direction between the inner surface and the outer surface, and the connecting portion having a second thickness in the one direction between the inner surface and the outer surface that is less than the first thickness.

16. A tube sheet assembly according to any one of claims 13 to 15, wherein the tube sheet is inclined at an angle of 30° relative to the longitudinal axis.

17. 1. A nuclear reactor system comprising: a reactor vessel extending along a longitudinal axis and positioned to contain a reactor core and a primary coolant, the primary coolant positioned to absorb heat from a nuclear reaction in the reactor core; Steam generator assembly and Including, The steam generator assembly includes: a first tube sheet assembly including a first tube sheet, the first tube sheet coupled to the furnace vessel and including a plurality of first perforations, the first tube sheet assembly including a flexible connection portion disposed between the first tube sheet and the furnace vessel, the flexible connection portion including an annular ring around the first tube sheet having a thickness less than a thickness of the first tube sheet, the annular ring including a flat portion offset parallel to a surface of the first tube sheet, the surface being inclined with respect to the longitudinal axis; a second tube sheet assembly including a second tube sheet, the second tube sheet being coupled to the reactor vessel and including a plurality of second perforations; a plurality of heat transfer tubes configured to receive a secondary coolant; Including, the secondary coolant is configured to absorb heat from the primary coolant through the heat transfer tubes; each of the heat transfer tubes has a first portion fluidly coupled to a corresponding one of the first perforations in the first tube sheet and a second portion fluidly coupled to a corresponding one of the second perforations in the second tube sheet.

18. 18. The nuclear reactor system of claim 17, wherein the first tube sheet assembly is positioned to receive the secondary coolant in liquid form and route the secondary coolant in liquid form through the first perforations to the heat transfer tubes, and the first tube sheet is inclined at an angle of 15° to 45° relative to the longitudinal axis.

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