Thermoelectric power conversion system including a heat pipe and a photovoltaic cell

Abstract

A power generation system, such as a nuclear power generation system, is described. An exemplary power generation system includes a heat source, a heat pipe, and a thermophotovoltaic cell. The heat pipe includes a first region and a second region. The first region is positioned to absorb heat from the heat source, and the second region is positioned to radiate at least a portion of the absorbed heat as thermal radiation from the heat pipe. The thermophotovoltaic cell is positioned to receive thermal radiation from the second region of the heat pipe and convert at least a portion of the thermal radiation into electrical energy. The power generation system may further include another heat pipe positioned to remove waste heat from the thermophotovoltaic cell.

Description

Technical Field

[0001] (Cross - Reference to Related Applications) This application claims the benefit of U.S. Provisional Patent Application No. 63 / 066,532, entitled "THERMAL POWER CONVERSION SYSTEM FOR A MICRO - REACTOR INCLUDING HEAT PIPES AND PHOTOVOLTAIC CELLS", filed on August 17, 2020, and U.S. Provisional Patent Application No. 63 / 175,428, entitled "THERMAL PHOTOVOLTAIC(TPV)DECAY HEAT REMOVAL AND / OR POWER CONVERSION SYSTEMS", filed on April 15, 2021, each of which is hereby incorporated by reference in its entirety.

[0002] This technology relates to a thermoelectric power conversion system including heat pipes that radiate thermal energy to photovoltaic cells used in nuclear reactor systems and the like.

Background Art

[0003] Power plants come in various shapes and sizes. Large - scale power plants can be used to supply power to a geographical area, while relatively small - scale power plants can be used, for example, to supply power to a region, a submarine, a spaceship, etc. Power plants can be used not only to supply power but also for countless additional or different purposes, from desalination of seawater to the creation of nuclear isotopes for medical purposes. Similarly, the types of available power plants cover a wide range of technologies, such as gas power generation, coal - fired power generation, nuclear power generation, etc. For use in space applications, portable applications, etc., it is often desirable to minimize the size and weight of the power plant. At the same time, it is desirable to increase the simplicity and reliability of the power plant.

[0004] Many aspects of the present technology can be better understood by referring to the following drawings. The components of the drawings are not necessarily to scale. Instead, emphasis is placed on clearly showing the principles of the present technology.

Summary of the Invention

[0005] Aspects of the present disclosure are generally directed to power generation systems, such as nuclear power generation systems, and related methods. In some embodiments described below, a representative power generation system includes a heat source, a heat pipe, and a thermophotovoltaic cell. The heat pipe includes a first region and a second region. The first region is configured to absorb heat from the heat source, and the second region is configured to radiate at least a portion of the absorbed heat from the heat pipe as heat radiation. The thermophotovoltaic cell is disposed to receive the heat radiation from the second region of the heat pipe and is configured to convert at least a portion of the heat radiation into electrical energy.

[0006] In some embodiments, the heat pipe is a first heat pipe, and the power generation system may further include a second heat pipe disposed to remove waste heat from the thermophotovoltaic cell. For example, the thermophotovoltaic cell can be attached to the second pipe so that waste heat can be conductively transferred from the thermophotovoltaic cell to the second heat pipe. The second heat pipe can release the waste heat to a heat sink or other source. In this way, the second heat pipe can function as a heat pipe management system for the thermophotovoltaic cell, removing waste heat from the thermophotovoltaic cell and maintaining the thermophotovoltaic cell at or below its maximum operating temperature.

[0007] In some embodiments, the heat pipe and the thermophotovoltaic cell are included in one of a plurality of groups of heat pipes and thermophotovoltaic cells. In such embodiments, the groups can be arranged vertically and / or circumferentially around the heat source to provide a compact arrangement with a large surface area for the thermophotovoltaic cells.

Brief Description of the Drawings

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Figure 5A

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Figure 5B

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DETAILED DESCRIPTION OF THE INVENTION

[0018] To fully understand the various embodiments of the present technology, the following description and specific details are shown in FIGS. 1-8. In other examples, in many cases, well-known structures, materials, operations, and / or systems associated with nuclear reactors, heat pipes, thermophotovoltaic cells, etc. are not shown in detail in the following disclosure and are not described in order to avoid unnecessarily obscuring the description of the various embodiments of the present technology. However, those skilled in the art will recognize that the present technology can be implemented without one or more of the details described herein and / or in combination with other structures, methods, components, etc. The terms used hereinafter should be interpreted in the broadest and most reasonable manner, even when used in conjunction with the detailed description of specific examples of embodiments of the present technology.

[0019] The accompanying drawings illustrate embodiments of the present technology and are not intended to limit its scope unless otherwise indicated. The sizes of the various elements depicted are not necessarily drawn to scale, and these various elements may be enlarged for ease of reading. Details of components are abstracted in the drawings such that details such as the position of components and specific exact connections between components are excluded when they are not necessary for a complete understanding of how the present technology is made and used. Many of the details, dimensions, angles, and other features shown in the drawings merely illustrate specific embodiments of the present disclosure. Accordingly, other embodiments may have other details, dimensions, angles, and features without departing from the present technology. Further, those skilled in the art will understand that further embodiments of the present technology can be implemented without some of the details described hereinafter.

[0020] FIG. 1 is a side cross-sectional view of a power generation system ( "System 100") configured in accordance with an embodiment of the present technology. FIGS. 2-4 are an isometric view, a top view, and a side view of System 100, respectively. Referring together to FIGS. 1-4, System 100 may include a heat source 102 and a plurality of first heat pipes 110 thermally coupled to the heat source 102. The first heat pipe 110 is configured to remove heat from the heat source 102 and radiate heat toward a plurality of thermophotovoltaic (TPV) or photovoltaic (PV) panels or cells 120. The TPV cell 120 is arranged to absorb the thermal radiation from the first heat pipe 110 and is configured to convert the thermal radiation into electrical energy and transmit it through one or more electric wires 103 (FIG. 1). In the illustrated embodiment, System 100 further includes a plurality of second heat pipes 130 thermally coupled to the TPV cell 120 and configured to maintain the TPV cell 120 at or below its maximum operating temperature by removing waste heat from the TPV cell 120.

[0021] In some embodiments, as shown in FIG. 1, the heat source 102 may be a nuclear reactor system ( "nuclear reactor 102"). Referring to FIG. 1, the nuclear reactor 102 may include a reactor vessel 101 that houses a reactor core 104 in which a controlled nuclear reaction takes place. In the illustrated embodiment, the reactor vessel 101 is cylindrical or capsule-shaped (e.g., having a circular cross-section), but in other embodiments, the reactor vessel 101 may be spherical, conical, or of other shapes and / or may have other cross-sectional shapes (e.g., elliptical, linear, rectangular, polygonal, irregular). The reactor core 104 may include one or more fuel assemblies 105 that contain fissionable material and / or other suitable materials. In some embodiments, the nuclear reactor 102 may include a reflector 109 disposed around the reactor core 104, which returns neutrons to the reactor core 104 to facilitate the nuclear reaction taking place there.

[0022] In some embodiments, the reactor vessel 101 may further contain a working fluid or coolant 106 (e.g., primary coolant) that transfers heat from the core 104 to the first heat pipe 110. For example, as indicated by the arrow located within the reactor vessel 101, the coolant 106 is heated in the reactor vessel 104 towards the bottom of the reactor vessel 101. The heated primary coolant (e.g., water, liquid metal, regardless of the presence or absence of additives) rises from the core 104 through the core shroud 107 and into the riser pipe 108. The hot and buoyant coolant 106 continues to rise through the riser pipe 108, exits the riser pipe 108, and passes downward through the first heat pipe 110. As the coolant 106 descends and passes through the first heat pipe 110, the coolant 106 transfers heat to the first heat pipe 110 and then descends to the bottom of the reactor vessel 101 where the cycle begins again. Thus, since the cycle can be driven by the change in buoyancy of the coolant 106, the need for pumps, valves, or other active fluid control devices to move the coolant 106 can be reduced or eliminated.

[0023] The nuclear reactor 102 may further include a plurality of control systems and associated sensors (not shown). For example, the nuclear reactor 102 may include one or more control rods, liquid moderators, and / or other components for controlling the reaction rate of the fissile material in the core 104. In some embodiments, the coolant 106 is omitted, and the first heat pipe 110 may be thermally coupled directly to the core 104. For example, the nuclear fuel may be thermally coupled directly (e.g., attached) to the first heat pipe 110. In some embodiments, the nuclear reactor 102 may include some features similar or identical to any of the nuclear reactor systems described in detail in (i) U.S. Patent Application No. 17 / 071,838, entitled "HEAT PIPE NETWORKS FOR HEAT REMOVAL, SUCH AS HEAT REMOVAL FROM NUCLEAR REACTORS, AND ASSOCIATED SYSTEMS AND METHODS," filed on October 15, 2020, (ii) U.S. Patent Application No. 17 / 071,795, entitled "NUCLEAR REACTORS HAVING LIQUID METAL ALLOY FUELS AND / OR MODERATORS," filed on October 15, 2020, and / or (iii) U.S. Patent Application No. 17 / 168,118, entitled "SUPPORTS WITH INTEGRATED SENSORS FOR NUCLEAR REACTOR STEAM GENERATORS, AND ASSOCIATED SYSTEMS AND METHODS," filed on February 4, 2021, and / or may operate similarly or identically, and these are hereby incorporated by reference in their entirety into this specification.

[0024] Continuing to refer to FIG. 1, the first heat pipe 110, the TPV cell 120, and the second heat pipe 130 may be vertically (e.g., stacked) arranged in a plurality of groups 140 (e.g., layers, sets). In the illustrated embodiment, there are five groups 140 in the vertical direction, and each group 140 includes (i) two first heat pipes 110, (ii) two TPV cells 120, and (iii) one second heat pipe 130. In some embodiments, the groups 140 may at least partially overlap, for example, such that each of the groups 140 shares at least one of the first heat pipes 110 with another one of the groups 140. Thus, pairs of TPV cells 120 may be vertically interleaved between the plurality of first heat pipes 110, and the second heat pipe 130 may be vertically interleaved between each pair of TPV cells 120. In each group 140, one of the TPV cells 120 may face one of the first heat pipes 110, and the other of the TPV cells 120 may face the other of the first heat pipes 110.

[0025] Referring further to FIGS. 2-4, the plurality of groups 140 may be arranged circumferentially around the heat source 102 or vertically around the heat source 102. As best shown in FIG. 2, for example, twelve groups 140 are arranged circumferentially around the heat source 102 at each vertical height such that the system 100 includes a total of sixty (12x5) groups 140. In other embodiments, the number of groups 140 in the vertical and / or circumferential directions may be different, and / or the groups 140 may include more or fewer first heat pipes 110, TPV cells 120, and / or second heat pipes 130. Further, although the first heat pipe 110, the second heat pipe 130, and the TPV cell 120 are shown as extending generally horizontally (e.g., orthogonally) with respect to the longitudinal axis of the heat source 102, in other embodiments, one or more of the first heat pipe 110, the second heat pipe 130, and / or the TPV cell 120 may extend vertically (e.g., parallel) and / or at another angle with respect to the longitudinal axis.

[0026] In some embodiments, the first heat pipes 110 may be generally similar or identical to each other, the TPV cells 120 may be generally similar or identical to each other, and / or the second heat pipes 130 may be generally similar or identical to each other. For example, FIGS. 5A-5C are top views of one of the first heat pipes 110, one of the TPV cells 120, and one of the second heat pipes 130, respectively, in accordance with embodiments of the present technology.

[0027] Referring to FIG. 5A, each of the first heat pipes 110 (the "first heat pipe 110") may include a first region 512 (e.g., an evaporator region), a second region 514 (e.g., a heat insulation region) extending from the first region 512, and a third region 516 (e.g., a condenser region) extending from the second region 514 (collectively the "regions 512-516"). In the illustrated embodiment, the first region 512 and the second region 514 are in an elongated rectangular shape, while the third region 516 is in a trapezoidal shape. In some embodiments, the third region 516 has a larger surface area than the first region 512 and the second region 514. In other embodiments, the sizes, shapes, and / or dimensions of the regions 512-516 may be different. For example, the third region 516 may be rectangular.

[0028] Referring to FIG. 5B, each of the TPV cells 120 (the "TPV cell 120") may be in a trapezoidal shape and may be sized and shaped to substantially match the third region 516 of the first heat pipe 110. A part, substantially all, or all of the upper surface 522 of the TPV cell 120 may be covered with a circuit 524, such as a photovoltaic diode, for converting thermal energy into electrical energy. The lower surface of the TPV cell 120 (hidden in FIG. 5B) may include a thermally conductive material to facilitate removal of waste heat from the TPV cell 120 (e.g., to the second heat pipe 130, as will be described in more detail below).

[0029] Referring to FIG. 5C, similar to the first heat pipe 110 shown in FIG. 5A, each of the second heat pipes 130 (the "second heat pipes 130") may include a first region 532 (e.g., an evaporator region), a second region 534 (e.g., a heat insulation region) extending from the first region 532, and a third region 536 (e.g., a condenser region) extending from the second region 534 (collectively, the "regions 532-536"). In the illustrated embodiment, the second region 534 and the third region 536 are in an elongated rectangular shape, while the first region 532 is in a trapezoidal shape. In some embodiments, the first region 532 has a larger surface area than the first region 534 and the second region 536. Further referring to FIGS. 1-4, in some embodiments, the second and third regions 534 may have a greater thickness than the first region 532, which may have a greater width (e.g., along a radius axis perpendicular to the vertical axis) (e.g., along the vertical axis of the heat source 102). In other embodiments, the sizes, shapes, and / or dimensions of the regions 532-536 may be different. For example, the third region 536 may be rectangular.

[0030] Referring to FIGS. 5A-5C together, in some embodiments, the sizes and shapes (e.g., planar sizes and shapes) of the third region 516 of the first heat pipe 110, the TPV cell 120, and the first region 532 of the second heat pipe 130 may be generally similar or identical. As will be described in more detail below, these components may be vertically stacked on top of another component to provide a compact arrangement.

[0031] In some embodiments, the first heat pipe 110 and the second heat pipe 130 may have generally similar or identical structures and / or may operate generally similarly or identically. For example, each of the first heat pipe 110 and the second heat pipe 130 may include an outer casing that defines a channel (e.g., a cavity, a chamber) containing a working fluid. The channel of the first heat pipe 110 may extend from a first region 512 through a second region 514 to a third region 516, and the channel of the second heat pipe 130 may extend from a first region 532 through a second region 534 to a third region 536. The working fluid may be, for example, a two-phase (e.g., liquid phase and gas phase) material such as sodium or potassium. In some embodiments, the casing may be formed from steel, molybdenum, molybdenum alloy, molybdenum oxide-lanthanum, and / or other metal or ceramic materials. In some embodiments, each of the first heat pipe 110 and the second heat pipe 130 may include a structure disposed within the channel for transporting the working fluid in response to a pressure differential via capillary action. For example, each of the first heat pipe 110 and the second heat pipe 130 may include a wicking structure (e.g., a composite wick) for transporting the working fluid. In some embodiments, the first heat pipe 110 and the second heat pipe 130 may be generally similar or identical to any of the heat pipes described in detail in U.S. Patent Application No. 17 / 071,838, entitled "HEAT PIPE NETWORKS FOR HEAT REMOVAL, SUCH AS HEAT REMOVAL FROM NUCLEAR REACTORS, AND ASSOCIATED SYSTEMS AND METHODS," filed on October 15, 2020, which is hereby incorporated by reference in its entirety.

[0032] Referring to FIGS. 1-5C together, a first heat pipe 110 extends through a reactor vessel 101 to a heat source 102. More specifically, for each of the first heat pipes 110, a first region 512 may be disposed within the heat source 102, a third region 516 may be disposed outside the heat source 102, and a second region 514 may be disposed inside and / or outside the heat source 102. The TPV cell 120 may be installed on a corresponding one of the second heat pipes 130, and the second heat pipe 130 may extend outwardly from the TPV cell 120 away from the heat source 102. More specifically, each TPV cell 120 may be installed on the lower or upper surface of a corresponding first region 532 of one of the second heat pipes 130 (e.g., attached, coupled, thermally coupled, transported). The third region 516 of each first heat pipe 110 may be disposed on an adjacent first region 532 of the second heat pipe 130 so as to face a corresponding one of the circuits 526 of the TPV cell 120 installed thereon. That is, in each group 140, the third region 516 of the first heat pipe 110, the TPV cell 120, and the first region 532 of the second heat pipe 130 may be vertically stacked. Accordingly, each TPV cell 120 may be attached to one of the second heat pipes 130 and disposed so as to face an adjacent (e.g., corresponding) one of the third regions 516 of the first heat pipe 110.

[0033] In some aspects of the present technology, due to the complementary configurations (e.g., trapezoidal shape and the same or substantially similar sizes) of the third region 516 of the first heat pipe 110, the TPV cell 120, and the first region 532 of the second heat pipe 130, each TPV cell 120 is (i) generally or at least substantially entirely (e.g., 90% or more) facing one adjacent third region 516 of the first heat pipe 110, and (ii) ensured to be generally or at least substantially entirely (e.g., 90% or more) in contact with the first region 532 of the second heat pipe 130 to which the TPV cell 120 is attached. Further, as best seen in FIGS. 2 and 3, the trapezoidal shapes of the third region 516 of the first heat pipe 110, the TPV cell 120, and the first region 532 of the second heat pipe 130 can provide a nested arrangement that utilizes substantially all of the circumferential space of the heat source 102, thereby providing a compact design while maximizing the surface area (and, for example, the corresponding energy conversion density of the TPV cell 120).

[0034] During operation of system 100, heat source 102 (e.g., circulating coolant 106) transfers heat to a first region 512 of a first heat pipe 110. For each first heat pipe 110, the heat absorbed in the first region 512 evaporates (e.g., vaporizes) a working fluid in and / or within the first region 512, creating a pressure differential between the first region 512 and a third region 516. The pressure differential drives the evaporated working fluid from the first region 512 through a second region 514 to the third region 516. The working fluid cools and condenses in the third region 516, thereby transferring heat to the casing of the first heat pipe 110 in the third region 516 and then radiating heat from the first heat pipe 110. Thus, heat accumulates in the first region 512 and is removed from the third region 516 of the first heat pipe 110. In some embodiments, no heat is removed or added in the second region 514. In some embodiments, each of the first heat pipes 110 may be configured to return the condensed / cooled working fluid from the third region 516 to the first region 512 against the pressure gradient, where the working fluid may be reheated and vaporized again. For example, as detailed above, each of the first heat pipes 110 may include a wicking structure configured to pump the working fluid against the pressure gradient by capillary action. In other embodiments, the first heat pipes 110 may be arranged such that gravity and / or centrifugal force return the cooled and condensed working fluid to the first region 512.

[0035] Each of the TPV cells 120 is arranged to receive heat radiated from an adjacent one of the third regions 516 of the first heat pipe 110 within the same group 140. The circuitry 524 of the TPV cells 120 can convert heat radiation (e.g., received photons) into electrical energy (e.g., direct current power), which may be carried out from the TPV cells 120 via the electrical wires 103. In some embodiments, the electrical wires 103 may be connected to a single load or transmission path, while in other embodiments, the electrical wires 103 may transfer electrical energy to separate loads and / or transmission paths. In some embodiments, as shown in FIG. 1, the system 100 may optionally include a vacuum vessel 150 (shown in dashed lines) at least partially surrounding the TPV cells 120 and the first heat pipe 110. The vacuum vessel 150 may be configured to create / maintain a vacuum or partial vacuum between the TPV cells 120 and the third region 516 of the first heat pipe 110 and radiate thermal energy towards the TPV cells 120. The vacuum can increase the amount of heat radiation received by the TPV cells 120 from the first heat pipe 110, for example, by minimizing the amount of dust or other contaminants that could potentially impede the radiative transfer path between the first heat pipe 110 and the TPV cells 120. Further, each of the TPV cells 120 may be located at a relatively small distance from an adjacent one of the first heat pipes 110 to enhance the efficiency of the radiation received by the TPV cells 120 and convert it into electrical energy.

[0036] Since the TPV cell 120 receives thermal radiation from the first heat pipe 110, a portion of the radiation may not be converted to electrical energy by the circuit 524 and instead may be absorbed as waste heat that raises the temperature of the TPV cell 120. Since the TPV cell 120 is attached to a corresponding one of the first regions 532 of the second heat pipe 130, the TPV cell 120 can transfer (e.g., conduct) waste heat to the first region 532 of the second heat pipe 130. For each of the second heat pipes 130, the heat absorbed in the first region 532 evaporates (e.g., vaporizes) the working fluid in and / or within the first region 532, creating a pressure differential between the first region 532 and the third region 536. The pressure differential drives the evaporated working fluid from the first region 532 through the second region 534 to the third region 536. The working fluid is cooled and condensed in the third region 536, thereby transferring heat to the casing of the second heat pipe 130 in the third region 536 for removal from the second heat pipe 130. In this way, the second heat pipe 130 can function as a heat pipe system for the TPV cell 120 that removes waste heat from the TPV cell 120 and maintains the TPV cell 120 at or below its maximum operating temperature (e.g., at an optimal or desired operating temperature).

[0037] Thus, heat is accumulated in the first region 532 of the second heat pipe 130 by the TPV cell 120 and removed from the third region 536. In some embodiments, heat is not removed or added in the second region 534. In some embodiments, each of the second heat pipes 130 may be configured to return the condensed / cooled working fluid from the third region 536 to the first region 532 against the pressure gradient (e.g., via capillary and / or other forces), where the working fluid can be reheated and vaporized again.

[0038] In some embodiments, the second heat pipe 130 can transfer waste heat (e.g., radiatively, conductively) to a heat sink such as the ground (e.g., the surface of the moon, Mars, or the Earth), the atmosphere (e.g., the atmosphere of Mars or the Earth), or outer space. In some embodiments, the heat removed by the second heat pipe 130 can be used in a further process such as a process of heating soil containing ice to extract water. For example, at least a third region 536 of the second heat pipe 130 can be covered with soil containing ice so that the second heat pipe 130 releases heat to the soil. The soil may be encapsulated or covered with a flexible sheet (e.g., by bagging the soil) to capture water vapor evaporated from the soil. The soil (e.g., soil bags) can be exchanged when the ice content of the soil is depleted.

[0039] In some embodiments, the first heat pipe 110 operates at a high temperature such as 500 °C or higher, 700 °C or higher, 900 °C or higher, 1100 °C or higher, etc., and is configured to radiate heat. For example, when the heat source 102 is a nuclear reactor, the coolant 106 can have a temperature of about 900 °C or higher during operation. In some embodiments, the second heat pipe 130 is configured to operate at a relatively low temperature such as less than 100 °C, less than 75 °C, less than 50 °C, 25 °C - 50 °C or less, etc. (e.g., corresponding to the operating temperature of the TPV cell 120). Accordingly, the first heat pipe 110 may be referred to as a high-temperature heat pipe, and the second heat pipe 130 may be referred to as a low-temperature heat pipe. In some embodiments, the first heat pipe 110 and the second heat pipe 130 can have different configurations / arrangements to maximize the heat transfer coefficient for a specific high or low operating temperature. For example, the first heat pipe 110 and the second heat pipe 130 can have different working fluids, sizes, wicking structures, etc.

[0040] In some aspects of the present technology, the power conversion components of system 100 can operate without using valves or pumps. For example, coolant 106 may be passively heated by core 104, and each of the first heat pipes 110 may operate as a closed fluid system for removing heat from coolant 106 and radiating heat to TPV cells 120, and each of the second heat pipes 130 may similarly operate as a closed fluid system for removing waste heat from TPV cells 120. Thereby, compared with conventional power conversion systems such as systems including a Brayton power generation cycle, the complexity and related maintenance requirements of system 100 are reduced, thereby enhancing the reliability of system 100.

[0041] In other embodiments, system 100 may have other devices or systems for removing exhaust heat from TPV cells 120 in addition to, or in place of, second heat pipes 130. For example, a fluid (e.g., water) may be circulated passively or actively under TPV cells 120 to cool and remove exhaust heat from TPV cells 120.

[0042] FIG. 6 is a partial schematic side cross-sectional view of a power generation system (“system 600”) configured according to an additional embodiment of the present technology. System 600 may include some features that are at least generally similar or identical in structure and function to the corresponding features of system 100 described above with reference to FIGS. 1-5C, and may operate generally similarly or identically to system 100. For example, similar or identical components are identified by the same reference numerals shown in FIGS. 1-5C.

[0043] However, in the illustrated embodiment, system 600 further includes (i) a first heat removal system 650 (shown schematically) thermally coupled to a third region 536 of a first set 652 of second heat pipes 130, and (ii) a second heat removal system 654 (shown schematically) thermally coupled to a third region 536 of a second set 656 of second heat pipes 130. In the illustrated embodiment, the number of second heat pipes 130 in the first set 652 is greater than the number of second heat pipes 130 in the second set 656, but in other embodiments, the first set 652 may include fewer or the same number of second heat pipes 130 as the second set 656. In some embodiments, the TPV cells 120 associated with the first heat pipes 110 and second heat pipes 130 of the first set 652 (e.g., in the corresponding group 140 shown in FIGS. 1-4) can provide a primary power generation function, while the TPV cells 120 associated with the first heat pipes 110 and second heat pipes 130 of the second set 656 (e.g., in the corresponding group 140 shown in FIGS. 1-4) can provide decay heat removal. For example, in the illustrated embodiment, the first set 652 is located above the second set 656, where the coolant 106 is typically at a higher temperature and can thus transfer more heat and thermal energy to the first heat pipes 110 of the first set 652.

[0044] In some embodiments, the first heat removal system 650 may be different from the second heat removal system 654. For example, the first heat removal system 650 may be an active system configured to circulate water, air, other fluids, and / or other heat transfer media through a third region 536 of the second heat pipe 130 within the first set 652 via an active pump, circulation, etc., while the second heat removal system 654 may be a passive system for removing heat from the third region 536 of the second heat pipe 130 within the second set 656. In some embodiments, the second heat removal system 654 may be a pool of fluid (e.g., water), dirt, air interface, and / or other heat sinks configured to passively absorb decay heat from the second heat pipe 130 within the second set 656 (or may include it). In other embodiments, the first heat removal system 650 and the second heat removal system 654 may comprise the same passive or active heat removal system. In some aspects of the present technology, the second heat removal system 654 may operate to remove heat from the heat source 102 when the power of the first heat removal system 650 is lost (e.g., when the first heat removal system 650 is an active heat removal system). In some aspects of the present technology, the passive operation of the second heat removal system 654 can simplify the design of the system 600 by reducing or eliminating the need for other active thermal control systems (thereby, for example, increasing reliability).

[0045] FIG. 7 is a partial schematic side cross-sectional view of a power generation system (''system 700'') configured according to an additional embodiment of the present technology. System 700 may include some features that are at least generally similar or identical in structure and function to corresponding features of system 100 and / or system 600 described above with reference to FIGS. 1-6, and may operate generally similarly or identically to system 100 and / or system 600. For example, similar or identical components are identified by the same reference numerals shown in FIGS. 1-6.

[0046] However, in the illustrated embodiment, system 700 further includes a heat exchanger 760, such as a steam generator, that includes a secondary coolant or working fluid (e.g., steam and water). The heat exchanger 760 is operably coupled to a power conversion system 770 and is configured to heat the secondary coolant and direct the heated secondary coolant to the power conversion system 770, which uses the heat from the secondary coolant to generate power and / or provide other useful outputs. The heat exchanger 760 and the power conversion system 770 together may be referred to as a primary power generation system, a primary power conversion system, and the like. In the illustrated embodiment, the heat exchanger 760 includes a first fluid header 762 (e.g., a feedwater header), a second fluid header 764 (such as a steam header) above the first fluid header 762, and a number of conduits 766 that extend between and fluidly couple the first and second fluid headers 762, 764. In some embodiments, as schematically shown in FIG. 7, the heat exchanger 760 is disposed around the upper portion of the riser row 108 such that the conduits 766 are circumferentially disposed around the riser tube 108, for example, in a helical pattern.

[0047] In the illustrated embodiment, the power conversion system 770 includes a turbine 772, a generator 774, a condenser 776, and a pump 778. During operation of the system 700, the primary coolant 106 heated by the core 104 rises through the riser tubes 108, exits the riser tubes 108, and passes downward through the conduit 766 of the heat exchanger 760 to heat the secondary coolant contained within the heat exchanger 760. The heated secondary coolant may rise through the conduit 766 to the second fluid header 764, where the heated secondary coolant is directed to the power conversion system 770. In some embodiments, the secondary coolant may vaporize while rising through the conduit 766. The turbine 772 receives the heated (e.g., vaporized) secondary coolant and converts at least a portion of the thermal energy of the heated secondary coolant into electricity via the generator 774. The secondary coolant may exit the turbine 772 at a reduced pressure before being condensed in the condenser 776 and is then directed to the first fluid header 762 (e.g., via the pump 778). Thereafter, the secondary coolant rises through the conduit 766 and is heated again. In some embodiments, the power conversion system 770 includes one or more valves and / or other fluid control devices (not shown) configured to control the rate of the secondary coolant to and / or from the first fluid header 762, thereby controlling the power generated by the power conversion system 770.

[0048] In the illustrated embodiment, system 700 includes a fewer number of groups 140 than systems 100 and 600 described above with reference to FIGS. 1-6, and the groups 140 are disposed below heat exchanger 760. Thus, during normal operation of system 700, the primary coolant 106 may have a higher temperature closer to the heat exchanger 760 than to the groups 140, and more thermal energy can be transferred to the heat exchanger. In other embodiments, system 700 may include more or fewer groups 140, and / or the groups 140 may be differently arranged. For example, in some embodiments, one or more groups 140 may be additionally or alternatively disposed adjacent to the heat exchanger 760 (e.g., at the same vertical position along riser tube 108).

[0049] In some embodiments, the heat exchanger 760 and the power conversion system 770 can provide a primary power generation function, while the group 140 of the first heat pipe 110, the TPV cell 120, and the second heat pipe 130 can provide decay heat removal. As described in detail above, the group 140 is configured to passively remove heat from the heat source 102 and is "always on". In some aspects of the present technology, this can reduce the number of controls required for the system 700 while enhancing the reliability of the system 700. Further, in some embodiments, the electrical energy generated by the TPV cell 120 can be transferred via the wire 103 to supply power to one or more control systems, safety systems, and / or other systems related to the heat source 102 and / or other components of the system 700. That is, for example, the power generated via the power conversion system 770 can be mainly directed to an external load, while the power generated via the TPV cell 120 can be mainly directed to a load related to the operation of the system 700. In some aspects of the present technology, due to the passive and continuous removal of decay heat provided by the group 140, the power generated via the TPV cell 120 is reliable and can be continuously provided in the event of a failure of the primary power conversion system 770. In an additional aspect of the present technology, the TPV cell 120 can continuously generate power even when the heat source 102 is operating at a minimum power level (e.g., when the core 104 is operating near hot zero power). In some aspects of the present technology, this power can be used to facilitate an easy restart of the reactor 104.

[0050] FIG. 8 is a side cross-sectional view of a power generation system ("system 800") configured in accordance with an additional embodiment of the present technology. The system 800 may include some features that are at least generally similar or identical in structure and function to the corresponding features of the systems 100, 600, and / or 700 described in detail above with reference to FIGS. 1-7, and may operate in a manner that is generally similar or identical to the systems 100, 600, and / or 700. For example, similar or identical components are identified by the same reference numerals shown in FIGS. 1-7.

[0051] However, in the illustrated embodiment, system 800 includes one or more TPV cells 820 that are disposed outside the heat source 102 and face the reactor vessel 101. In some embodiments, the coolant 106 heated by the core 104 may heat the reactor vessel 101, which radiates heat toward the TPV cells 820 (e.g., as indicated by the arrows in FIG. 8). The TPV cells 820 are arranged to absorb the thermal radiation from the reactor vessel 101 and are configured to convert the thermal radiation into electrical energy and transmit it on one or more electrical wires 803. In some embodiments, system 800 may further include a heat removal system 880 that is thermally coupled to the TPV cells 820 and is configured to remove waste heat from the TPV cells 820, thereby maintaining the TPV cells 820 below their maximum operating temperature. The heat removal system 880 may include an active or passive air, water, and / or other fluid cooling system, and / or may include one or more heat pipes thermally coupled to the TPV cells 820. Thus, in the illustrated embodiment, since the reactor vessel 101 can directly radiate thermal energy to the TPV cells 120, there is no need to include any intermediate heat pipes (e.g., the first heat pipe 110 of FIGS. 1-7) for removing and radiating thermal energy from within the reactor vessel 101. In other embodiments, the TPV cells 820 may be arranged to receive the thermal energy radiated from the reactor vessel 101, while system 800 further includes one or more intermediate heat pipes. That is, for example, the TPV cells 820 and the associated heat removal system 880 may be arranged around any of the systems 100, 600, and / or 700 described in detail above to provide additional power generation. For example, although the heat exchanger 760 and the power conversion system 770 of FIG. 7 provide primary power generation, the arrangement of the TPV cells 820 can be used for passive / decommissioning thermoelectric power conversion.

[0052] The following examples illustrate some embodiments of the present technology. (Example 1) A nuclear reactor including a core disposed inside a reactor vessel, The reactor core is configured to generate heat, a nuclear reactor, A surface arranged to receive the heat from the reactor core, and arranged to radiate at least a part of the heat received from the surface as heat radiation, A thermophotovoltaic cell arranged to receive the heat radiation from the surface and convert at least a part of the heat radiation into electrical energy A nuclear power generation system comprising (Example 2) Further comprising a heat pipe having a first region and a second region, the first region being configured to receive heat from the reactor core, and the second region including the surface, the nuclear power generation system of Example 1. (Example 3) The heat pipe is one of a plurality of first heat pipes each having the first region and the second region, the thermophotovoltaic cell is one of a plurality of thermophotovoltaic cells, and each of the thermophotovoltaic cells is configured to receive the heat radiation from the surface of the corresponding second region of the first heat pipe and convert at least a part of the heat radiation into electrical energy, the first region of the first heat pipe is at least partially arranged inside the reactor vessel, and the second region of the first heat pipe is at least partially arranged outside the reactor vessel, A plurality of second heat pipes, each of the second heat pipes being thermally coupled to one or more thermophotovoltaic cells and arranged to transfer heat from the one or more thermophotovoltaic cells, the nuclear power generation system of Example 2 further comprising (Example 4) The heat pipe is a first heat pipe, further comprising a second heat pipe thermally coupled to the thermophotovoltaic cell, the second heat pipe being arranged to transfer heat from the thermophotovoltaic cell, the nuclear power generation system of Example 2 or Example 3. (Example 5) The thermophotovoltaic cell is arranged at a distance from the first heat pipe and attached to the second heat pipe, the nuclear power generation system of Example 4. (Example 6) The second heat pipe has a first region and a second region, the thermophotovoltaic cell is attached to the first region of the second heat pipe, and the second region of the second heat pipe is arranged to transfer heat to a heat sink. The nuclear power generation system of Example 4 or Example 5. (Example 7) In the nuclear power generation system of Example 6, the second region of the first heat pipe, the thermophotovoltaic cell, and the first region of the second heat pipe are overlapped with each other. (Example 8) In the nuclear power generation system of Example 6 or Example 7, the second region of the first heat pipe, the thermophotovoltaic cell, and the first region each have at least a substantially identical planar shape. (Example 9) In the nuclear power generation system of any one of Examples 2-8, the second region of the heat pipe has a trapezoidal cross-sectional shape. (Example 10) In the nuclear power generation system of Example 9, the thermophotovoltaic cell has a substantially similar trapezoidal cross-sectional shape, and the thermophotovoltaic cell is overlapped with the second region of the heat pipe. (Example 11) A nuclear reactor having a reactor core configured to generate heat, A plurality of heat pipes arranged to absorb heat from the reactor core and radiate at least a part of the heat from the heat pipe as heat radiation, A plurality of thermophotovoltaic cells arranged to absorb the heat radiation from one or more heat pipes and convert at least a part of the heat radiation into electrical energy A nuclear power generation system comprising. (Example 12) In the nuclear power generation system of Example 11, the nuclear reactor includes a reactor vessel that houses the reactor core, the heat pipes are arranged in a stack with respect to the reactor vessel, and at least one thermophotovoltaic cell is arranged between each pair of adjacent heat pipes in the stack. (Example 13) Each of the heat pipes includes a first region arranged to absorb heat from the core and a second region arranged to radiate the heat radiation. The second region of the heat pipe and the thermophotovoltaic cell have substantially the same shape and size, and the second region is superimposed on the thermophotovoltaic cell. Example 12 nuclear power generation system. (Example 14) The nuclear reactor includes a reactor vessel that houses the core. The heat pipes are arranged in a stack with respect to the reactor vessel. Two thermophotovoltaic cells are arranged between each pair of adjacent heat pipes in the stack. The first of the two thermophotovoltaic cells faces the first of the pair of adjacent heat pipes, and the second of the two thermophotovoltaic cells faces the second of the pair of adjacent heat pipes. Any one of Examples 11-13 nuclear power generation system. (Example 15) The heat pipe is a first heat pipe, and the nuclear power generation system further includes a plurality of second heat pipes. One of the second heat pipes is arranged between each pair of adjacent heat pipes in the stack, and the two thermophotovoltaic cells are attached to one of the second heat pipes arranged between the pair of adjacent heat pipes. Example 14 nuclear power generation system. (Example 16) The nuclear reactor includes a reactor vessel that houses the core. The heat pipes are arranged circumferentially around the reactor vessel, the thermophotovoltaic cells are arranged circumferentially around the reactor vessel, and the corresponding ones of the second heat pipes are superimposed. Any one of Examples 11-15 nuclear power generation system. (Example 17) The nuclear reactor includes a reactor vessel that houses the core. The heat pipes and the thermophotovoltaic cells are arranged in a plurality of groups that are arranged vertically and circumferentially around the reactor vessel. Each group includes (a) at least one heat pipe and (b) at least one thermophotovoltaic cell arranged to absorb the heat radiation from the at least one heat pipe. Any one of Examples 11-16 nuclear power generation system. (Example 18) Absorbing heat generated from the core of a nuclear reactor in a first region of a heat pipe; Radiating at least a portion of the heat as heat radiation from a second region of the heat pipe; Receiving the heat radiation in a thermophotovoltaic cell; Converting at least a portion of the heat radiation into electrical energy in the thermophotovoltaic cell; A method of power generation including these steps. (Example 19) The heat pipe is a first heat pipe, and the method further includes moving waste heat from the thermophotovoltaic cell using a second heat pipe, the method of Example 18. (Example 20) The method includes: Absorbing heat from the core using a coolant; Flowing the coolant through a portion of the heat pipe; The method of Example 18 or Example 19 further including these steps. (Example 21) A heat pipe having a first region and a second region, the first region configured to absorb heat from a heat source, the second region configured to radiate at least a portion of the absorbed heat as heat radiation from the heat pipe; and A thermophotovoltaic cell configured to receive the heat radiation from the second region of the heat pipe and convert at least a portion of the heat radiation into electrical energy. A power generation system comprising these components. (Example 22) The heat pipe is a first heat pipe, and the power generation system of Example 21 further includes a second heat pipe thermally coupled to the thermophotovoltaic cell, the second heat pipe configured to move heat from the thermophotovoltaic cell. (Example 23) The thermophotovoltaic cell is disposed spaced apart from the first heat pipe and attached to the second heat pipe, the power generation system of Example 22. (Example 24) The second heat pipe has a first region and a second region, the thermophotovoltaic cell is attached to the first region of the second heat pipe, and the second region of the second heat pipe is arranged to transfer heat to a heat sink. The power generation system of Example 22 or Example 23. (Example 25) The second region of the first heat pipe, the thermophotovoltaic cell, and the first region of the second heat pipe are superposed on each other. The power generation system of Example 24. (Example 26) The second region of the first heat pipe, the thermophotovoltaic cell, and the first region each have at least a substantially identical planar shape. The power generation system of Example 24 or Example 25. (Example 27) The second region of the heat pipe has a trapezoidal cross-sectional shape. The power generation system of any one of Examples 21-26. (Example 28) The thermophotovoltaic cell has a substantially similar trapezoidal cross-sectional shape, and the thermophotovoltaic cell is superposed on the second region of the heat pipe. The power generation system of Example 27. (Example 29) The power generation system of any one of Examples 21-28, further comprising the heat source. (Example 30) The heat source includes a nuclear reactor. The power generation system of any one of Examples 21-29. (Example 31) A heat source, A plurality of heat pipes arranged to absorb heat from the heat source and radiate at least a part of the heat from the heat pipe as heat radiation, A plurality of thermophotovoltaic cells arranged to absorb the heat radiation from one or more heat pipes and convert at least a part of the heat radiation into electrical energy A power generation system comprising. (Example 32) The heat pipes are arranged in a stack with respect to the heat source, and at least one thermophotovoltaic cell is arranged between each pair of adjacent heat pipes in the stack. The power generation system of Example 31. (Example 33) Each of the heat pipes includes a first region arranged to absorb heat from the heat source and a second region arranged to radiate the heat radiation. The second region of the heat pipe and the thermophotovoltaic cell have substantially the same shape and size, and the second region is superposed with the thermophotovoltaic cell. The power generation system of Example 32. (Example 34) The heat pipe is arranged in a stack with respect to the heat source, and two thermophotovoltaic cells are arranged between each pair of adjacent heat pipes in the stack. A first one of the two thermophotovoltaic cells faces a first one of the pair of adjacent heat pipes, and a second one of the two thermophotovoltaic cells faces a second one of the pair of adjacent heat pipes. The power generation system according to any one of Examples 31-33. (Example 35) The heat pipe is a first heat pipe, and the power generation system further includes a plurality of second heat pipes. One of the second heat pipes is arranged between each pair of adjacent heat pipes in the stack, and the two thermophotovoltaic cells are attached to one of the second heat pipes arranged between the pair of adjacent heat pipes. The power generation system of Example 34. (Example 36) The heat pipe is arranged circumferentially around the heat source, the thermophotovoltaic cell is arranged circumferentially around the heat source, and the corresponding heat pipe in the second heat pipe is superposed. The power generation system according to any one of Examples 31-35. (Example 37) The heat pipe and the thermophotovoltaic cell are arranged in a plurality of groups arranged vertically and circumferentially around the heat source. Each group includes (a) at least one heat pipe and (b) at least one thermophotovoltaic cell arranged to absorb the heat radiation from the at least one heat pipe. The power generation system according to any one of Examples 31-36. (Example 38) The step of absorbing heat from the heat source in the first region of the heat pipe, and radiating at least a portion of the heat as heat radiation from a second region of the heat pipe; receiving the heat radiation in a thermophotovoltaic cell; converting at least a portion of the heat radiation into electrical energy in the thermophotovoltaic cell A method for power generation, comprising: (Example 39) The heat pipe is a first heat pipe, The method further includes transferring waste heat from the thermophotovoltaic cell using a second heat pipe, as in Example 38. (Example 40) The method further includes generating the heat at the heat source via a nuclear reaction, as in Example 38 or Example 39. (Example 41) A nuclear reactor including a reactor core disposed inside a reactor vessel, a plurality of first heat pipes, each of which includes a first region and a second region, the first region being at least partially disposed inside the reactor vessel and configured to absorb heat generated from the reactor core, the second region being at least partially disposed outside the reactor vessel and configured to radiate at least a portion of the absorbed heat from the first heat pipe as heat radiation, a plurality of thermophotovoltaic cells, each of which receives the heat radiation from a corresponding one of the second regions of the first heat pipes and is arranged to convert at least a portion of the heat radiation into electrical energy, a plurality of second heat pipes, each of which is thermally coupled to one or more thermophotovoltaic cells and is arranged to transfer heat from the one or more thermophotovoltaic cells A nuclear power generation system comprising:

[0053] The above detailed description of the embodiments of the technology is not intended to be exhaustive or to limit the technology to the exact forms disclosed above. Specific embodiments and examples of the technology are described above for illustrative purposes, but as will be recognized by those skilled in the art, various equivalent modifications are possible within the scope of the technology. For example, although the steps are shown in a given order, other embodiments may perform the steps in a different order. Also, various embodiments described herein may be combined to provide further embodiments.

[0054] Accordingly, while specific embodiments of the technology have been described herein for illustrative purposes, it will be understood that in order to avoid unnecessarily obscuring the description of the embodiments of the technology, well-known structures and functions are not shown in detail. Where the context permits, the singular or plural terms may also include the plural or singular terms, respectively.

[0055] As used herein, phrases such as "A and / or B" with "and / or" refer to only A, only B, and A and B. The present disclosure is governed to the extent that materials incorporated herein by reference are inconsistent with the present disclosure. Further, the term "comprising" is used throughout to mean including at least the recited (plural) features so as not to exclude additional types of the same features and / or other features. Also, while specific embodiments are described herein for purposes of illustration, it will be understood that various changes may be made without departing from the technology. Further, while the advantages associated with some embodiments of the technology are described in the context of those embodiments, other embodiments may also exhibit such advantages, and not all embodiments necessarily exhibit such advantages in order to fall within the scope of the technology. Accordingly, the present disclosure and related technologies may include other embodiments not explicitly shown or described herein.

Claims

1. A nuclear reactor including a reactor core disposed within a reactor vessel, the reactor core being configured to generate heat, and a first heat pipe having a first region and a second region, the first region including a surface configured to receive heat from the reactor core and configured to radiate at least a portion of the heat received as thermal radiation from the surface, a thermophotovoltaic cell configured to receive the thermal radiation from the surface and configured to convert at least a portion of the thermal radiation into electrical energy wherein the second region of the first heat pipe has a trapezoidal cross-sectional shape, and the upper base of the trapezoid faces the reactor vessel, the thermophotovoltaic cell has a substantially similar trapezoidal cross-sectional shape and is superimposed on the second region of the first heat pipe, a nuclear power generation system.

2. The nuclear power generation system according to claim 1, wherein the first region is configured to receive heat from the reactor core.

3. The first heat pipe is one of a plurality of first heat pipes, the thermophotovoltaic cell is one of a plurality of thermophotovoltaic cells, each of the thermophotovoltaic cells is configured to receive the thermal radiation from the surface of a corresponding one of the second regions of the first heat pipes and is arranged to convert at least a portion of the thermal radiation into electrical energy, the first region of the first heat pipe is at least partially disposed inside the reactor vessel, and the second region of the first heat pipe is at least partially disposed outside the reactor vessel, and a plurality of second heat pipes, each of the second heat pipes being thermally coupled to one or more thermophotovoltaic cells and arranged to transfer heat from the one or more thermophotovoltaic cells, the nuclear power generation system according to claim 2 further comprising a second heat pipe.

4. The nuclear power generation system according to claim 2, further comprising a second heat pipe thermally coupled to the thermophotovoltaic cell, the second heat pipe being arranged to transfer heat from the thermophotovoltaic cell.

5. The nuclear power generation system according to claim 4, wherein the thermophotovoltaic cell is disposed at a distance from the first heat pipe and is attached to the second heat pipe.

6. The second heat pipe has a first region and a second region, the thermophotovoltaic cell is attached to the first region of the second heat pipe, and the second region of the second heat pipe is arranged to transfer heat to a heat sink. The nuclear power generation system according to claim 4.

7. The second region of the first heat pipe, the thermophotovoltaic cell, and the first region of the second heat pipe are superposed on one another. The nuclear power generation system according to claim 6.

8. The second region of the first heat pipe, the thermophotovoltaic cell, and the first region of the second heat pipe each have at least a substantially identical planar shape. The nuclear power generation system according to claim 6.

9. The nuclear reactor includes a reactor vessel that houses the reactor core, the first heat pipe is arranged circumferentially around the reactor vessel, and the thermophotovoltaic cell is arranged circumferentially around the reactor vessel. The nuclear power generation system according to claim 1.

10. A nuclear reactor having a reactor core configured to generate heat, A plurality of heat pipes that absorb heat from the reactor core, the heat pipes being arranged so as to radiate at least a part of the heat as heat radiation from the heat pipes, A plurality of thermophotovoltaic cells that absorb the heat radiation from one or more heat pipes and are arranged to convert at least a part of the heat radiation into electrical energy are provided, The nuclear reactor includes a reactor vessel that houses the reactor core, the heat pipes and the thermophotovoltaic cells are arranged in a plurality of groups that are arranged vertically and circumferentially around the reactor vessel, and each group includes (a) at least one heat pipe and (b) at least one thermophotovoltaic cell arranged to absorb the heat radiation from the at least one heat pipe. A nuclear power generation system.

11. The heat pipes are arranged in a stack with respect to the reactor vessel, and at least one thermophotovoltaic cell is arranged between each pair of adjacent heat pipes in the stack. The nuclear power generation system according to claim 10.

12. Each of the heat pipes includes a first region arranged to absorb heat from the core and a second region arranged to emit the heat radiation, the second region of the heat pipe and the thermophotovoltaic cell have substantially the same shape and size, and the second region is superposed with the thermophotovoltaic cell. The nuclear power generation system according to claim 11.

13. The heat pipe is arranged in a stacked manner with respect to the reactor vessel, two thermophotovoltaic cells are arranged between each pair of adjacent heat pipes in the stack, a first one of the two thermophotovoltaic cells faces a first one of the pair of adjacent heat pipes, and a second one of the two thermophotovoltaic cells faces a second one of the pair of adjacent heat pipes. The nuclear power generation system according to claim 10.

14. The heat pipe is a first heat pipe, the nuclear power generation system further includes a plurality of second heat pipes, one of the second heat pipes is arranged between each pair of adjacent heat pipes in the stack, and the two thermophotovoltaic cells are attached to one of the second heat pipes arranged between the pair of adjacent heat pipes. The nuclear power generation system according to claim 13.

15. The heat pipe is arranged circumferentially around the reactor vessel, the thermophotovoltaic cell is arranged circumferentially around the reactor vessel, and is superposed with a corresponding one of the second heat pipes. The nuclear power generation system according to claim 10.

16. Absorbing heat generated from the core of the nuclear reactor in the first region of the heat pipe; Radiating at least a part of the heat as heat radiation from the second region of the heat pipe; Receiving the heat radiation in the thermophotovoltaic cell; Converting at least a part of the heat radiation into electrical energy in the thermophotovoltaic cell and including The heat pipe and the thermophotovoltaic cell are arranged in a plurality of groups vertically and circumferentially around a reactor vessel that houses the core, and each group includes (a) at least one heat pipe and (b) at least one thermophotovoltaic cell arranged to absorb the heat radiation from the at least one heat pipe. A method of generating electricity.

17. The heat pipe is a first heat pipe, and the method according to claim 16 further includes a step of transferring waste heat from the thermophotovoltaic cell using a second heat pipe. **Claim 18** The method includes further steps of absorbing heat from the core using a coolant and flowing the coolant through a part of the heat pipe, and is the method according to claim 16.

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