Device, system and method for cooling a nuclear reactor with a hydride moderator

Abstract

Disclosed herein is a heat exchanger for cooling a nuclear reactor core. The heat exchanger may include a first stage including an input configured to receive a working fluid from an external source into the heat exchanger and a first plenum configured to surround a moderator heat pipe extending from the reactor core. The heat exchanger may further include a second stage including an output configured to remove working fluid from the heat exchanger to the external source and a second plenum configured to surround a power heat pipe extending from the reactor core, the first plenum and the second plenum being in fluid communication and configured such that the external fluid must travel through the first plenum and over the moderator heat pipe before entering the second plenum and traveling over the power heat pipe.

Description

[Technical Field]

[0001] The present disclosure relates generally to nuclear power generation, and more particularly to neutron moderation provided by hydride moderators in thermal spectrum or quasi-thermal spectrum heat pipe reactors at high temperatures. Summary of the Invention

[0002] The following summary is provided to facilitate an understanding of some of the innovative features unique to the embodiments disclosed herein and is not intended to be a complete description, although a full understanding of the various embodiments can be obtained by taking the entire specification, claims, and abstract into consideration as a whole.

[0003] In various aspects, a heat exchanger for cooling a nuclear reactor core is disclosed. The heat exchanger can include a first stage including an input configured to receive a working fluid from an external source into the heat exchanger and a first plenum configured to surround a moderator heat pipe extending from the reactor core. The heat exchanger can further include a second stage including an output configured to remove the working fluid from the heat exchanger to the external source and a second plenum configured to surround a power heat pipe extending from the reactor core, the first plenum and the second plenum being in fluid communication and configured such that the external fluid must travel through the first plenum and over the moderator heat pipe before entering the second plenum and traveling over the power heat pipe.

[0004] In various aspects, a system is disclosed. The system can include a nuclear reactor core, the reactor core including a moderator heat pipe coupled to a moderator cell positioned within the reactor core and a power heat pipe coupled to a fuel cell positioned within the reactor core. The system can further include a heat exchanger, the heat exchanger including a first plenum configured to surround the moderator heat pipe and a second plenum configured to surround the power heat pipe. The first plenum and the second plenum are in fluid communication, and the first plenum and the second plenum are configured such that an external fluid must travel through the first plenum and around the moderator heat pipe before entering the second plenum and traveling around the power heat pipe.

[0005] In various aspects, a method of cooling a nuclear reactor core is disclosed that includes introducing an external working fluid into a first stage of a two-stage heat exchanger via a first plenum input, transferring thermal energy through the working fluid away from a moderator heat pipe extending from the reactor core, introducing the working fluid through a fluid path into a second stage of the two-stage heat exchanger, transferring thermal energy through the working fluid away from a power heat pipe extending from the core of the nuclear reactor, and converting the thermal energy transferred away from the moderator heat pipe and the thermal energy transferred away from the power heat pipe to usable energy via a power conversion subsystem.

[0006] These and other objects, features, and characteristics of the present invention, its associated elements of construction, method of operation and function, combination of parts and economies of manufacture, will become more apparent from a consideration of the following description and appended claims, all of which form a part of this specification, with reference to the accompanying drawings, in which like reference numerals designate corresponding parts in the various views, but it is to be expressly understood that the drawings are for the purpose of illustration and description only and are not intended as a definition of the limits of this invention. [Brief explanation of the drawings]

[0007] Various features of the aspects described herein are set forth with particularity in the appended claims. However, the various aspects, both as to organization and method of operation, together with their advantages, may be understood by reference to the following description taken in conjunction with the accompanying drawings, as follows:

[0008] [Figure 1] 1 illustrates a cross-sectional view of an improved system for cooling a nuclear reactor with a hydride moderator in accordance with at least one non-limiting embodiment of the present disclosure.

[0009] [Figure 2] 1 illustrates another cross-sectional view of an improved system for cooling a nuclear reactor with a hydride moderator in accordance with at least one other non-limiting aspect of the present disclosure.

[0010] [Figure 3] 1 illustrates another cross-sectional view of an improved system for cooling a nuclear reactor with a hydride moderator in accordance with at least one other non-limiting aspect of the present disclosure.

[0011] [Figure 4] 1 illustrates another cross-sectional view of an improved system for cooling a nuclear reactor with a hydride moderator in accordance with at least one other non-limiting aspect of the present disclosure.

[0012] [Figure 5] 5 illustrates a cross-sectional view of a scalable core of a nuclear reactor configured to be cooled via any of the systems of FIGS. 1-4 in accordance with at least one non-limiting embodiment of the present disclosure.

[0013] [Figure 6] 1 illustrates a flow diagram of an improved method for cooling a nuclear reactor with a hydride moderator in accordance with at least one non-limiting embodiment of the present disclosure.

[0014] Corresponding reference characters indicate corresponding parts throughout the several views. The embodiments presented herein illustrate various aspects of the present invention in one form and such embodiments should not be construed as limiting the scope of the present invention in any manner. DETAILED DESCRIPTION OF THE INVENTION

[0015] Numerous specific details have been set forth to provide a thorough understanding of the overall structure, function, manufacture, and use of the embodiments as described in this disclosure and illustrated in the accompanying drawings. Well-known operations, components, and elements have not been described in detail so as not to obscure the embodiments described herein. The reader will understand that the embodiments described and illustrated herein are non-limiting examples, and thus, it will be understood that specific structural and functional details disclosed herein may be representative and illustrative. Modifications and variations thereto may be made without departing from the scope of the claims. Furthermore, it should be understood that terms such as "front," "rear," "left," "right," "upward," and "downward" are words of convenience and should not be construed as limiting terms.

[0016] Before describing the various aspects of the various heat exchangers disclosed in detail herein, it should be noted that the illustrative examples are not limited in application or use to the details of construction and arrangement of parts illustrated in the accompanying drawings and description. The illustrative examples may be implemented in or incorporated into other aspects, variations, and modifications, and may be practiced or carried out in various ways. Furthermore, unless otherwise indicated, the terms and phrases used herein have been chosen for the convenience of the reader and for the purpose of describing the illustrative examples, not for the purpose of limiting them. It will also be understood that one or more of the aspects, aspect expressions, and / or examples described below can be combined with any one or more of the other aspects, aspect expressions, and / or examples described below.

[0017] As nuclear reactors continue to decrease in size, heat pipe-based cooling systems have emerged as a means to facilitate more simplified reactor designs. For example, heat pipes utilize a closed system characterized by a small amount of condensable gas (e.g., working fluid) that achieves a relatively high heat transfer rate over a relatively small cross-sectional area. The simplified and compact nature of such designs makes them suitable for implementation in microreactors. Additionally, heat pipe-based systems require no active or moving parts because heat generated by the reactor can be removed using an array of heat pipes with a working fluid (e.g., sodium, potassium, etc.) transported via capillary or wicking through three regions (e.g., evaporator region, condenser region, and adiabatic region). The working fluid removes thermal energy from the reactor's heat-producing core through the evaporator region of the heat pipes and transports the thermal energy to the condenser region of the heat pipes, which is connected to a power conversion system configured to convert the heat into usable energy (e.g., electricity, etc.).

[0018] However, hydride moderators have also emerged as a viable means for improving core neutronics and, therefore, the overall performance and efficiency of nuclear reactors. For example, the efficiency of a nuclear reactor is determined by the temperature of the heat produced by the core and the environment to which that heat is rejected. As this temperature difference increases, the theoretical maximum efficiency of the overall system also increases. Therefore, it is desirable to operate nuclear reactors at higher temperatures. While hydride moderators can improve neutron economy, some hydride materials—e.g., yttrium hydride and zirconium hydride—generally undergo hydrogen dissociation at high temperatures, which can degrade the hydride's moderating capabilities. However, given the simplified design of heat pipe-based cooling systems for nuclear reactors, it would be counterintuitive to introduce a separate active system to maintain a lower temperature in the hydride moderator itself. Therefore, there is a need for improved devices, systems, and methods for cooling nuclear reactors with hydride moderators. Such devices, systems, and methods may modify the arrangement of heat pipes, moderators, and other nuclear materials to achieve higher temperature differentials across the reactor and maintain the stability of hydride moderator materials without increasing design complexity or otherwise compromising the aforementioned benefits of heat pipe cooling systems.

[0019] Referring now to FIG. 1 , an improved system 100 for cooling a nuclear reactor with a hydride moderator is depicted in accordance with at least one non-limiting embodiment of the present disclosure. According to the non-limiting embodiment of FIG. 1 , the system 100 may include a reactor core 101 portion, a heat exchanger 103 portion, and a power conversion subsystem 104 portion. The system 100 may further include a plurality of heat pipes 105 a-c, 107 a, 107 b, including one or more power heat pipes 105 a-c (collectively, “105”) and one or more moderator heat pipes 107 a, 107 b (collectively, “107”). As previously discussed, an evaporator region of each heat pipe 105, 107 of the plurality of heat pipes may be positioned within the reactor core 101 portion, and a condenser portion of each heat pipe 105, 107 of the plurality of heat pipes may be positioned within the power conversion subsystem 104. The adiabatic region—or the region where heat does not enter or leave the closed system—of each heat pipe 105, 107 of the plurality of heat pipes can be disposed between the condenser section and the evaporator section. According to a non-limiting embodiment of FIG. 1 , seals can connect the heat exchanger section 103 to the power heat pipes 105 and the moderator heat pipes 107 of the reactor core 101 section.

[0020] 1 , one or more moderator heat pipes 107 are configured to transfer thermal energy away from moderator cells in the reactor core 101 portion, which may contain hydride materials, such as yttrium hydride and zirconium hydride. As previously discussed, transferring thermal energy away from the moderator cells can ensure that hydrogen does not dissociate from the hydride, which may occur at high temperatures, including temperatures typical during reactor core operation. As depicted in FIG. 1 , a second, separate set of heat pipes 105 can be configured to transfer thermal energy away from fuel cells in the reactor core 101 portion, which may contain fissile material or any material capable of undergoing a nuclear fission reaction. Specifically, the power heat pipes 105 can be arranged within the reactor core 101 portion such that they penetrate or are otherwise engaged with the fuel cells in the reactor core 101 portion. The moderator cells and fuel cells in the reactor core 101 portion of the system 100 can be thermally insulated from each other, which allows the fuel cells to operate at higher temperatures while maintaining lower moderator cell temperatures to prevent hydrogen dissociation.

[0021] 1 , each heat pipe 105, 107 of the plurality of heat pipes may have a working fluid (e.g., sodium, potassium, etc.) that evaporates and / or condenses as it travels the length of the pipe 105, 107 and encounters different thermal environments in the system 100. An external working fluid (e.g., air, helium, etc.) may be introduced into the system 100 via an input 109 of a first plenum 106 and removed from the system 100 via an output 111 of a second plenum 108 as a means of cooling each heat pipe 105, 107 of the plurality of heat pipes to ensure that neither the moderator cell nor the fuel cell reaches a critical temperature at which heat is no longer optimally removed from the system 100.

[0022] 1 , to prevent hydrogen dissociation, it would be preferable if the system 100 were configured so that the one or more moderator heat pipes 107 are cooled by the external working fluid before being exposed to the power heat pipes 105. Although the first plenum 106 is in fluid communication with the second plenum 108, the first plenum 106 is configured so that the external working fluid enters via the inlet 109 and travels first over the moderator heat pipes 107. When the external working fluid reaches the end of the heat exchanger 103 portion of the system 100, it first encounters the one or more power heat pipes 105 before returning full circle to the second plenum 108 and exiting the system 100 toward the power conversion subsystem 104. Additionally, the parallelism of the conduits through which the first plenum 106 and the second plenum 108 are in fluid communication reflects the arrangement of the heat pipes 105, 107 of the system 100 and promotes heat transfer from the heat pipes to the external working fluid.

[0023] 1 is configured to function as a two-stage power conversion heat exchanger. The first plenum 106 and the second plenum 108 are in fluid communication with each other only via conduits that force the external working fluid to travel through the moderator heat pipes 107 before traveling through the power heat pipes 105. Thus, in the first stage of the two-stage system 100, the external working fluid transfers thermal energy away from the moderator heat pipes 107, and in the second stage of the two-stage system 100, the external working fluid transfers thermal energy away from the power heat pipes 105. In the second stage, the power heat pipes 105 are arranged in a second set of parallel channels that are configured to facilitate the transfer of thermal energy from the power heat pipes 105 to the external working fluid to remove heat from portions of the reactor core 101 for conversion into usable energy (e.g., electricity). This can be accomplished by the power conversion subsystem 104, which can be configured as a Brayton system. The power conversion subsystem 104 can be either an open system or a closed system, depending on the user's preference and / or the intended application.

[0024] 1 ensures that the external working fluid is at its lowest temperature before traveling through one or more moderator heat pipes 107, resulting in an optimal amount of heat energy being transferred away from the moderator cells and mitigating the risk of hydrogen dissociation within the moderator cells. If this configuration were reversed, the external working fluid would contain the heat energy transferred away from the power heat pipes 105 before encountering the moderator heat pipes 107, thereby reducing the amount of heat energy transferred away from the moderator heat pipes 107 and increasing the risk of hydrogen dissociation.

[0025] It should be understood, therefore, that system 100 of FIG. 1 provides: (1) a temperature differential between the first and second stages; (2) insulation between the fissile material and the moderator; and (3) substantial heat generation within the core that is limited to the fissile material. These features enable system 100 of FIG. 1 to operate moderator cells within the reactor core 101 portion at substantially lower temperatures and fuel cells within the reactor core 101 portion at substantially higher temperatures than conventional systems. Thus, system 100 produces more optimal levels of energy while preventing hydrogen dissociation within the moderator cells. While the non-limiting embodiment of FIG. 1 depicts a specific system 100 configuration that provides the aforementioned features and benefits, it should be understood that the present disclosure contemplates, according to other non-limiting embodiments, systems of varying configurations designed to implement similar features and achieve benefits similar to those of the specific system 100 of FIG. 1.

[0026] For example, referring now to Figure 2, another improved system 200 for cooling a nuclear reactor with a hydride moderator is depicted in accordance with at least one other non-limiting embodiment of the present disclosure. According to the non-limiting embodiment of Figure 2, a reactor core 201 portion of system 200 is integrated with and / or positioned within an enclosure for a heat exchanger 203 portion of system 200. However, like the non-limiting embodiment of system 100 of Figure 1, system 200 of Figure 2 again includes a plurality of heat pipes 205a-c, 207a, 207b, including one or more power heat pipes 205a-c (collectively, "205") and one or more moderator heat pipes 207a, 207b (collectively, "207").

[0027] 2, similar to the heat pipes 105, 107 of the system 100 of FIG. 1, one or more moderator heat pipes 207 may be configured to transfer thermal energy away from the moderator cells of the reactor core 201 portion, and one or more power heat pipes 205 may be configured to transfer thermal energy away from the fuel cells of the reactor core 201 portion. Each heat pipe 205, 207 of the plurality of heat pipes may contain a working fluid (e.g., sodium, potassium, etc.) that is configured to evaporate and / or condense as the working fluid travels the length of the pipe 205, 207 and encounters different thermal environments of the system 200. An external working fluid (e.g., air, helium, etc.) may again be introduced into the system 200 via an input 209 of the first plenum 206 and removed from the system 200 via an output 211 of the second plenum 208.

[0028] 2 are in fluid communication with each other only via conduits that force the external working fluid to travel through the moderator heat pipes 207 before traveling through the power heat pipes 205. In the first stage of the two-stage system 200, the external working fluid transfers thermal energy away from the moderator heat pipes 207, while in the second stage of the two-stage system 200, the external working fluid transfers thermal energy away from the power heat pipes 205. In the second stage, the power heat pipes 205 are arranged in a second set of parallel channels that are configured to facilitate the transfer of thermal energy from the power heat pipes 205 to the external working fluid to remove heat from portions of the reactor core 201 for conversion into usable energy (e.g., electricity) via the power conversion subsystem 204. Power conversion subsystem 204 can be configured similarly to power conversion subsystem 104 of system 100 of Figure 1. The two-stage configuration of system 200 of Figure 2 ensures that the external working fluid is at its lowest temperature before traveling through one or more moderator heat pipes 207, which results in an optimal amount of heat energy being transferred away from the moderator cells and mitigates the risk of hydrogen dissociation within the moderator cells.

[0029] 2, the reactor core 201 portion of the system 200 may be integrated with and / or positioned within the enclosure of the heat exchanger 203 portion of the system 200. As such, the system 200 of FIG. 2 eliminates the need to seal the heat exchanger portion 203 to the one or more power heat pipes 205 and one or more moderator heat pipes 207 used by the reactor core 201 portion of the system 200 because the heat pipes 205, 207 are already positioned within the heat exchanger portion 203 and are therefore in fluid communication with the first plenum 206 and the second plenum 208. For example, the system 100 of FIG. 1 may require seals to maintain an inventory of the power conversion system's working fluid and / or to prevent air (more specifically, oxygen) from entering regions of the reactor core where it may react with materials in the reactor core, causing harmful oxidation. However, sealing the heat pipes can be challenging due to expected thermal expansion. Additionally, according to a non-limiting embodiment, where systems 100 and 200 use a working fluid optimized for closed systems (e.g., helium), the size of the working fluid molecules can complicate seals. Thus, system 200 of FIG. 2, like system 100 of FIG. 1, can produce optimal levels of energy while preventing hydrogen dissociation within the moderator cells, yet without the need for seals. This can reduce design complexity, reduce expected maintenance costs, and mitigate potential failure modes.

[0030] Referring now to FIG. 3, another improved system 300 for cooling a nuclear reactor with a hydride moderator is depicted in accordance with at least one other non-limiting embodiment of the present disclosure. Similar to systems 100, 200 of FIGS. 1 and 2, system 300 of FIG. 3 is structured as a two-stage power conversion heat exchanger configured to transfer energy away from a plurality of heat pipes 305a-c, 307a, 307b, including one or more power heat pipes 305a-c (collectively, “305”) and one or more moderator heat pipes 307a, 307b (collectively, “307”). Again, system 300 may include a reactor core 301 portion. However, according to the non-limiting embodiment of FIG. 3, system 300 may further include a first-stage first heat exchanger 303a portion disposed on an opposite side of reactor core 301 portion relative to second-stage heat exchanger 303b portion. This configuration may be preferred when the moderator heat pipes 307 and power heat pipes 305 enter the reactor core 301 portion from both sides. Nevertheless, as depicted in Figure 3, the first stage first heat exchanger 303a portion may be in fluid communication with the second stage first heat exchanger 303b portion via fluid path P. For example, the first stage first heat exchanger 303a portion may be ducted with connected piping, thereby forming fluid path P, although other means of establishing fluid communication are contemplated by the present disclosure.

[0031] 3 through an input 309 of the first plenum 306 of the first stage first heat exchanger 303a section, where the external working fluid transfers thermal energy away from one or more moderator heat pipes 307 before traveling along fluid path P to enter the second stage heat exchanger 303b section. Once in the second stage heat exchanger 303b section, the external working fluid transfers thermal energy away from one or more power heat pipes 307 before exiting the system 300 via an output 311 of the second plenum 308 to the power conversion subsystem 304. The power conversion subsystem 304 may be configured similarly to the power conversion subsystems 104, 204 of FIGS. 1 and 2 and may convert thermal energy removed from the heat pipes 305, 307 into usable energy (e.g., electricity, etc.). Therefore, the system 300 of Figure 3 is also able to produce optimal levels of energy while preventing hydrogen dissociation within the moderator cells via the first stage first heat exchanger 303a section and the second stage first heat exchanger 303b section.

[0032] Referring now to FIG. 4, another improved system 400 for cooling a nuclear reactor with a hydride moderator is depicted in accordance with at least one other non-limiting aspect of the present disclosure. Similar to system 200 of FIG. 2, system 400 of FIG. 4 may include a reactor core 401 portion integrated with and / or positioned within an enclosure of a heat exchanger 403 portion of system 400. However, similar to system 300 of FIG. 3, system 400 of FIG. 4 may further include moderator heat pipes 407a, 407b (collectively, “407”) and power heat pipes 405a-c (collectively, “405”) entering the reactor core 401 portion of system 400 from both sides. Thus, system 400 of FIG. 4 may include an input 409 of a first plenum 406 disposed on the opposite side of the reactor core 401 portion from an output 411 of a second plenum 408 of the heat exchanger 403 portion.

[0033] 4, an external working fluid (e.g., air, helium, etc.) can be introduced into the system 400 of FIG. 4 via an input 409 in a first plenum 406 where, during a first stage, the external working fluid travels over one or more moderator heat pipes 407 and transfers thermal energy away from the one or more moderator heat pipes 407 before traveling around portions of the reactor core 401 to a second stage where the external working fluid travels over one or more power heat pipes 407 and transfers thermal energy away from the one or more power heat pipes 407. The external fluid can then exit the system 400 via an output 411 in a second plenum 408 to the power conversion subsystem 404. The power conversion subsystem 404 can be configured similarly to the power conversion subsystems 104, 204, and 304 of Figures 1-3 and can convert the thermal energy removed from the heat pipes 405 and 407 into usable energy (e.g., electricity, etc.). Therefore, the system 400 of Figure 4 can also generate optimal levels of energy while preventing hydrogen dissociation within the moderator cells via the two-stage heat exchanger 403. However, the system 400 of Figure 4 can eliminate the need to seal the heat pipes 405 and 407 to the heat exchanger 403, as in the system 200 of Figure 2.

[0034] Referring now to Figure 5, a cross-sectional view of a scalable core of a nuclear reactor 500 configured to be cooled via any of the systems of Figures 1-4 is depicted in accordance with at least one non-limiting embodiment of the present disclosure. According to the non-limiting embodiment of Figure 5, the nuclear reactor 500 can include a plurality of fuel cells 501 with a plurality of moderator cells 505 interspersed throughout the plurality of fuel cells 501. As depicted in Figure 5, the moderator cells 505 can be separated from adjacent fuel cells 501 by insulating layers 503, which enable the fuel cells 501 to operate at a desired high reactor temperature, while the moderator cells 505 operate at a lower temperature, which can prevent dissociation of hydrogen from the hydride moderator material. 5 includes a hexagonal configuration, it should be understood that, according to other non-limiting embodiments, the cells 501, 505 can include alternative geometric shapes (e.g., rectangular, triangular, octagonal, etc.) such that the core 500 can assume any other shape. According to some non-limiting embodiments, the cells 501, 505 can be geometrically configured to allow the core 500 to be scalable in terms of power output while remaining suitable for use with a two-stage heat exchanger, as discussed in more detail below.

[0035] 5, the core may include a plurality of moderator heat pipes 507a-e (collectively "507") traveling through moderator cells 505 and a plurality of power heat pipes 509a-h (collectively "509") traveling through fuel cells 501. Heat pipes 507, 509 may extend from core 500 into a two-stage heat exchanger configured similar to any of heat exchanger portions 103, 203, 303, 403 of FIGS. 1-4, such that thermal energy is transferred away from moderator heat pipes 507 in the first stage and thermal energy is transferred away from power heat pipes 509 in the second stage. Thus, core 500 of FIG. 5 may produce optimal levels of energy while preventing hydrogen dissociation in moderator cells 505 via the two-stage heat exchanger. It should be noted that the cells 501, 505 of the core 500 of FIG. 5 are configured to allow two dedicated sets of heat pipes 507, 509 to be used for energy transfer, thereby making the core 500 suitable for use with a two-stage heat exchanger.

[0036] Referring now to FIG. 6 , a flow diagram of an improved method 600 for cooling a nuclear reactor with a hydride moderator is depicted in accordance with at least one non-limiting embodiment of the present disclosure. For example, the method 600 of FIG. 6 can be implemented via any of the aforementioned systems 100, 200, 300, and 400 described with reference to FIGS. 1-4 . According to the non-limiting embodiment of FIG. 6 , the method 600 can include introducing 602 an external working fluid into a first stage of a two-stage heat exchanger via a first plenum input. Once the working fluid is introduced into the first stage of the heat exchanger, the method 600 can further include transferring 604 thermal energy via the working fluid away from a moderator heat pipe extending from the nuclear reactor core. After the thermal energy is transferred away from the moderator heat pipe, the method 600 can include introducing 606 the working fluid into a second stage of the two-stage heat exchanger via a fluid path. Once the working fluid is introduced into the second stage of the heat exchanger, the method 600 may further include transferring 608 thermal energy via the working fluid away from a power heat pipe extending from the nuclear reactor core. According to certain non-limiting embodiments, the method 600 may further include converting the thermal energy transferred away from the moderator heat pipe and the thermal energy transferred away from the power heat pipe into usable energy, such as electricity, via a power conversion subsystem.

[0037] Various aspects of the subject matter described herein are presented in the following numbered clauses.

[0038] Item 1. A heat exchanger for cooling a nuclear reactor core, comprising a first stage and a second stage, wherein the first stage comprises an input configured to receive a working fluid from an external source into the heat exchanger and a first plenum configured to surround a moderator heat pipe extending from the core of the nuclear reactor, and the second stage comprises an output configured to remove working fluid from the heat exchanger to the external source and a second plenum configured to surround a power heat pipe extending from the reactor core, the first plenum and the second plenum being in fluid communication and configured such that the external fluid must travel through the first plenum and over the moderator heat pipe before entering the second plenum and traveling over the power heat pipe.

[0039] Clause 2. The heat exchanger of clause 1, wherein the external source comprises a power conversion subsystem configured to convert thermal energy from the working fluid received from the output into usable energy.

[0040] Item 3. The heat exchanger of item 1, wherein the usable energy includes electricity.

[0041] Item 4. The heat exchanger of item 1, wherein the first stage is disposed on an opposite side of the reactor core from the second stage.

[0042] Clause 5. The heat exchanger of clause 4, further comprising a duct configured to form a fluid path between the first plenum and the second plenum, the duct traveling outside the reactor core.

[0043] Item 6. The heat exchanger of item 1, further comprising a seal configured to connect the heat exchanger to the power heat pipe and the moderator heat pipe.

[0044] Item 7. Further comprising an enclosure configured to surround the first stage of the heat exchanger, the second stage of the heat exchanger, and the reactor core; Item 1. The heat exchanger of item 1, wherein the first stage of the heat exchanger, the second stage of the heat exchanger, and the reactor core are positioned within the enclosure.

[0045] Item 8. The heat exchanger of item 1, wherein the moderator heat pipe is coupled to a moderator cell of the reactor core.

[0046] Clause 9. The heat exchanger of clause 1, wherein the moderator cells of the reactor core include hydrides, and the first stage of the heat exchanger is configured to transfer thermal energy in a direction away from the moderator heat pipe.

[0047] Item 10. A system comprising a reactor core and a heat exchanger, wherein the reactor core comprises a moderator heat pipe coupled to a moderator cell positioned within the reactor core, and a power heat pipe coupled to a fuel cell positioned within the reactor core, and the heat exchanger comprises a first plenum configured to surround the moderator heat pipe and a second plenum configured to surround the power heat pipe, the first plenum and the second plenum being fluidly connected and configured such that an external fluid must travel through the first plenum and around the moderator heat pipe before entering the second plenum and traveling around the power heat pipe.

[0048] Clause 11. The system of clause 10, further comprising a power conversion subsystem in fluid communication with the second plenum, the power conversion subsystem configured to receive the working fluid from the second plenum and convert thermal energy from the working fluid into usable energy.

[0049] Item 12. The system of claim 11, wherein the usable energy is electricity.

[0050] Clause 13. The system of clause 10, wherein the first plenum is disposed on an opposite side of the reactor core from the second plenum.

[0051] Clause 14. The system of clause 13, further comprising a duct configured to form a fluid path between the first plenum and the second plenum, the duct traveling outside the reactor core.

[0052] Clause 15. The system of clause 10, further comprising a seal configured to connect the heat exchanger to the power heat pipe and the moderator heat pipe.

[0053] Clause 16. The system of clause 10, wherein the heat exchanger further comprises an enclosure configured to surround the first plenum of the heat exchanger, the second plenum of the heat exchanger, and the reactor core, and the first plenum, the second plenum, and the reactor core are positioned within the enclosure.

[0054] Clause 17. The system of clause 10, wherein the moderator cells of the reactor core include a hydride.

[0055] Clause 18. The system of clause 17, wherein the first plenum is configured to transfer thermal energy away from the moderator heat pipe, thereby reducing the amount of hydrogen dissociated from the hydride.

[0056] Item 19. A method for cooling a nuclear reactor core, the method comprising: introducing an external working fluid into a first stage of a two-stage heat exchanger via an input in a first plenum; transferring thermal energy through the working fluid away from a moderator heat pipe extending from the nuclear reactor core; introducing the working fluid into a second stage of the two-stage heat exchanger via a fluid path; transferring thermal energy through the working fluid away from a power heat pipe extending from the nuclear reactor core; and converting the thermal energy transferred away from the moderator heat pipe and the thermal energy transferred away from the power heat pipe into usable energy via a power conversion subsystem.

[0057] Clause 20. The method of clause 19, wherein the nuclear reactor core comprises a moderator containing a hydride, and the method further comprises reducing an amount of hydrogen dissociated from the hydride in the moderator via the thermal energy transferred away from the moderator heat pipe.

[0058] All patents, patent applications, publications, or other disclosure materials mentioned herein are incorporated by reference in their entirety, as if each individual reference were expressly incorporated by reference. All references and any material, or portions thereof, said to be incorporated by reference herein are incorporated herein only to the extent that the incorporated material does not conflict with existing definitions, descriptions, or other disclosed material set forth in this disclosure. Therefore, and to the extent necessary, the disclosure as set forth herein supersedes any conflicting material incorporated by reference herein, and the disclosure as set forth in this application takes precedence.

[0059] The present invention has been described with reference to various exemplary and illustrative embodiments. The embodiments described herein are understood to provide illustrative features of varying detail of various aspects of the disclosed invention. Thus, unless otherwise specified, it is understood that, to the extent possible, one or more features, elements, components, ingredients, constituent materials, structures, modules, and / or aspects of these disclosed embodiments can be combined, separated, interchanged, and / or rearranged with or with one or more other features, elements, components, ingredients, constituent materials, structures, modules, and / or aspects of the disclosed embodiments without departing from the scope of the disclosed invention. Thus, as will be recognized by those skilled in the art, various substitutions, modifications, or combinations of any of these exemplary embodiments can be made without departing from the scope of the invention. Additionally, those skilled in the art will, upon review of this specification, recognize or be able to ascertain using no more than routine experimentation, many equivalents to the various aspects of the invention described herein. Accordingly, the invention is not limited by these detailed descriptions of the various aspects, but rather by the claims.

[0060] Those skilled in the art will recognize that the terms used herein generally, and in the appended claims in particular (e.g., the body of the appended claims), are generally intended as "open" terms (e.g., the term "including" should be interpreted as "including, but not limited to," the term "having" should be interpreted as "having at least," the term "includes" should be interpreted as "including, but not limited to," etc.). Those skilled in the art will further understand that where a specific number of introduced claim recitations is intended, such intention will be clearly set forth in the claim; where such recitations are absent, such intention is not present. For example, as an aid to understanding, the following appended claims may include the use of the introductory phrases "at least one" and "one or more" to introduce claim recitations. However, the use of such phrases should not be construed as implying that the introduction of claim matter with the indefinite article "a" or "an" limits any particular claim that includes such introduced claim matter to claims that include only one such matter, even when the introductory phrase "one or more" or "at least one" and the indefinite article "a" or "an" appear within the same claim (e.g., "a" and / or "an" should typically be interpreted to mean "at least one" or "one or more"). The same applies to the use of definite articles used to introduce claim matter.

[0061] Additionally, even when a specific number of introduced claim items is explicitly recited, those skilled in the art will recognize that such items should typically be interpreted to mean at least the recited number (e.g., "two items," without any other modifier, typically means at least two items or more than two items). Furthermore, in instances where language similar to "at least one of A, B, and C, etc." is used, such syntax is generally intended in the sense that those skilled in the art would understand the language (e.g., "a system having at least one of A, B, and C" includes, but is not limited to, systems having only A, only B, only C, both A and B, both A and C, both B and C, and / or all of A, B, and C, etc.). In instances where language similar to "at least one of A, B, or C, etc." is used, such syntax is generally intended in the sense that one of ordinary skill in the art would understand the language (e.g., "a system having at least one of A, B, or C" includes, but is not limited to, systems having only A, only B, only C, both A and B, both A and C, both B and C, and / or all of A, B, and C, etc.). As will be further understood by those of ordinary skill in the art, disjunctive words and / or phrases typically presenting two or more alternative terms, whether in the specification, claims, or drawings, should be understood to contemplate the possibility of including one of the terms, either of the terms, or both of the terms, unless the context otherwise requires. For example, the phrase "A or B" would typically be understood to include the possibilities of "A" or "B" or "A and B."

[0062] With respect to the appended claims, those skilled in the art will recognize that the actions recited therein generally may be performed in any order. Also, while the claimed subject matter is presented in a sequence, it should be understood that various actions may be performed in orders other than those recited, or may be performed simultaneously. Examples of such alternative orderings may include overlapping, interleaved, interrupted, reordered, incremental, preliminary, supplementary, simultaneous, reverse, or other various orderings, unless the context otherwise requires. Furthermore, terms such as "responsive to," "related to," or other past-tense adjectives are generally not intended to exclude such variations, unless the context otherwise requires.

[0063] It is worth noting that any reference to "one aspect," "an aspect," "an exemplification," "one exemplification," etc. means that the particular feature, structure, or characteristic described in connection with that aspect is included in at least one aspect. Thus, the appearances of the phrases "in one aspect," "in one embodiment," "in one embodiment," and "in one embodiment" in various places throughout the specification are not necessarily all referring to the same aspect. Furthermore, particular features, structures, or characteristics may be combined in any suitable manner in one or more aspects.

[0064] As used herein, the singular forms "a," "an," and "the" include plural referents unless the context clearly requires otherwise.

[0065] Directional terms used herein, such as, and without limitation, top, bottom, left, right, lower, upper, front, rear, and variations thereof, are intended to refer to the orientation of the elements as shown in the accompanying drawings and do not limit the claims, unless expressly stated otherwise.

[0066] The term "approximately" or "about," as used in this disclosure, unless otherwise specified, refers to an acceptable error for a particular value as calculated by one of ordinary skill in the art, which error depends in part on how the value is measured or calculated. In certain embodiments, the term "approximately" or "about" means within 1, 2, 3, or 4 standard deviations. In certain embodiments, the term "approximately" or "about" means within 50%, 200%, 105%, 100%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, or 0.05% of a given value or range.

[0067] In this specification, unless otherwise indicated, all numerical parameters should be understood in all instances to be preceded and modified by the term "approximately," where the numerical parameter possesses the inherent variability characteristic of the underlying measurement techniques used to calculate the numerical value of that parameter. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter set forth herein should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

[0068] Every numerical range described herein includes all subranges subsumed within the described range. For example, a range of "1 to 100" includes all subranges between (and including) the recited minimum of 1 and the recited maximum of 100, i.e., having a minimum of 1 or more and a maximum of 100 or less. Also, every range described herein includes the endpoints of the described range. For example, a range of "1 to 100" includes the endpoints 1 and 100. Every maximum numerical limit described herein is intended to include every subsumed lower numerical limit, and every minimum numerical limit described herein is intended to include every subsumed upper numerical limit. Therefore, applicants reserve the right to amend this specification, including the claims, to expressly describe any subranges encompassed within the expressly described ranges. All such ranges are inherently described herein.

[0069] Any patent application, patent, non-patent publication, or other disclosure material referenced in this specification and / or listed in any Application Data Sheet is incorporated herein by reference to the extent that the incorporated material is not inconsistent with this specification. Therefore, and to the extent necessary, the disclosure as expressly set forth herein supersedes any conflicting material incorporated by reference herein. Any material, or portion thereof, that is said to be incorporated herein by reference but that conflicts with existing definitions, descriptions, or other disclosure material set forth herein is incorporated only to the extent that no conflict arises between the incorporated material and the existing disclosure material.

[0070] The terms "comprise" (and all forms of "comprise," such as "comprises" and "comprising"), "have" (and all forms of "has" and "having"), "include" (and all forms of "includes" and "including"), and "contain" (and all forms of "contains" and "containing") are open-ended linking verbs. Consequently, a system that "comprises," "has," "includes," or "contains" one or more elements possesses those one or more elements, but is not limited to possessing only those one or more elements. Similarly, an element of a system, device, or apparatus that "comprises," "has," "includes," or "contains" one or more features possesses those one or more features, but is not limited to possessing those one or more features.

Claims

1. 1. A heat exchanger for cooling a nuclear reactor core, comprising: a first stage and a second stage; The first stage an input configured to receive a working fluid from an external source into the heat exchanger; a first plenum configured to surround a moderator heat pipe extending from the core of the nuclear reactor; Equipped with The second stage an output configured to remove working fluid from the heat exchanger to the external source; a second plenum configured to surround a power heat pipe extending from the reactor core; Equipped with a first plenum and the second plenum are in fluid communication and configured such that the external fluid must travel through the first plenum and over the moderator heat pipe before entering the second plenum and traveling over the power heat pipe; heat exchanger.

2. The heat exchanger of claim 1 , wherein the external source comprises a power conversion subsystem configured to convert thermal energy from the working fluid received from the output into usable energy.

3. The heat exchanger of claim 1 , wherein the usable energy comprises electricity.

4. 2. The heat exchanger of claim 1, wherein said first stage is disposed on an opposite side of said core of said nuclear reactor from said second stage.

5. a duct configured to form a fluid path between the first plenum and the second plenum; 5. The heat exchanger of claim 4, wherein the duct travels outside the reactor core.

6. The heat exchanger of claim 1 , further comprising a seal configured to connect the heat exchanger to the power heat pipe and the moderator heat pipe.

7. an enclosure configured to surround the first stage of the heat exchanger, the second stage of the heat exchanger, and the nuclear reactor core; 2. The heat exchanger of claim 1, wherein the first stage of the heat exchanger, the second stage of the heat exchanger, and the nuclear reactor core are positioned within the enclosure.

8. The heat exchanger of claim 1 , wherein the moderator heat pipe is coupled to a moderator cell of the nuclear reactor core.

9. the moderator cells of the reactor core contain hydrides; The heat exchanger of claim 1 , wherein the first stage of the heat exchanger is configured to transfer thermal energy away from the moderator heat pipe.

10. 1. A system comprising: a nuclear reactor core and a heat exchanger; The reactor core comprises: a moderator heat pipe coupled to a moderator cell positioned within the reactor core; a power heat pipe coupled to a fuel cell positioned within the reactor core; Equipped with The heat exchanger is a first plenum configured to surround the moderator heat pipe; a second plenum configured to surround the power heat pipe; Equipped with the first plenum and the second plenum are in fluid communication and are configured such that an external fluid must travel through the first plenum and around the moderator heat pipe before entering the second plenum and traveling around the power heat pipe.

11. a power conversion subsystem in fluid communication with the second plenum; The system of claim 10 , wherein the power conversion subsystem is configured to receive the working fluid from the second plenum and convert thermal energy from the working fluid into usable energy.

12. The system of claim 11 , wherein the available energy is electricity.

13. The system of claim 10 , wherein the first plenum is disposed on an opposite side of the reactor core from the second plenum.

14. The system of claim 13 , further comprising a duct configured to form a fluid path between the first plenum and the second plenum, the duct traveling exterior to the nuclear reactor core.

15. The system of claim 10 , further comprising a seal configured to connect the heat exchanger to the power heat pipe and the moderator heat pipe.

16. the heat exchanger further comprising an enclosure configured to surround the first plenum of the heat exchanger, the second plenum of the heat exchanger, and the reactor core; The system of claim 10 , wherein the first plenum, the second plenum, and the reactor core are positioned within the enclosure.

17. The system of claim 10 , wherein the moderator cells of the nuclear reactor core include a hydride.

18. 20. The system of claim 17, wherein the first plenum is configured to transfer thermal energy away from the moderator heat pipe to reduce an amount of hydrogen dissociated from the hydride.

19. 1. A method for cooling a nuclear reactor core, comprising: introducing an external working fluid into a first stage of a two-stage heat exchanger via an input in a first plenum; transferring thermal energy through the working fluid in a direction away from a moderator heat pipe extending from the reactor core; introducing the working fluid into a second stage of the two-stage heat exchanger via a fluid path; transferring thermal energy through the working fluid in a direction away from a power heat pipe extending from the core of the nuclear reactor; converting the thermal energy transferred away from the moderator heat pipe and the thermal energy transferred away from the power heat pipe into usable energy via a power conversion subsystem; A method comprising:

20. the reactor core comprises a hydride-containing moderator; 20. The method of claim 19, further comprising reducing an amount of hydrogen dissociated from the hydrides in the moderator via the thermal energy transferred away from the moderator heat pipe.

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