Passive residual heat removal system for lunar reactor and lunar reactor

Abstract

The embodiments of this application relate to the field of removing residual heat from a reactor after shutdown, specifically to a passive residual heat removal system suitable for a lunar reactor and a lunar reactor itself. The lunar reactor includes a core, core heat transfer elements, and thermoelectric conversion elements disposed outside the core. The passive residual heat removal system includes a first heat transfer element and a second heat transfer element. The first heat transfer element is thermally connected to each core heat transfer element outside the core; the second heat transfer element is thermally connected to the first heat transfer element and is configured such that: when the lunar reactor is operating normally, the second heat transfer element does not conduct heat from the first heat transfer element; when a lunar reactor accident occurs, as the core temperature rises, the second heat transfer element passively activates to conduct heat from the first heat transfer element to the outside. The passive residual heat removal system provided by the embodiments of this application helps to avoid affecting the thermoelectric conversion efficiency of the lunar reactor during normal operation; and can passively remove core heat during a lunar reactor accident.

Description

Technical Field

[0001] Embodiments of this application relate to the field of removing residual heat from a reactor shutdown, specifically to a passive residual heat removal system applicable to a lunar reactor and the lunar reactor itself. Background Technology

[0002] The statements herein are provided merely as background information in connection with this application and do not necessarily constitute prior art.

[0003] Establishing a lunar base on the lunar surface would facilitate better lunar exploration. Nuclear power sources (i.e., lunar reactors) could be used to power the lunar base. The safety of these lunar reactors is crucial for the sustainable development of the lunar base.

[0004] Currently, there are still some safety issues with lunar reactors. Summary of the Invention

[0005] A brief overview of this application is provided below to offer a basic understanding of certain aspects thereof. It should be understood that this overview is not an exhaustive summary of the application. It is not intended to identify key or essential parts of the application, nor is it intended to limit its scope. Its purpose is merely to present certain concepts in a simplified form as a prelude to the more detailed description that follows.

[0006] Embodiments of this application provide a passive waste heat removal system suitable for lunar reactors and a lunar reactor.

[0007] In a first aspect, embodiments of this application provide a passive residual heat removal system suitable for a lunar reactor. The lunar reactor includes a core, at least one core heat transfer element, and at least one thermoelectric conversion element disposed outside the core. The core provides heat, the core heat transfer element conducts the heat from the core to the corresponding thermoelectric conversion element, and the thermoelectric conversion element converts the heat from the core into electrical energy. The passive residual heat removal system may include a first heat transfer element and a second heat transfer element. The first heat transfer element is disposed outside the core and is thermally connected to each core heat transfer element. The second heat transfer element is connected to the first heat transfer element and is configured such that: when the lunar reactor is operating normally, the second heat transfer element does not conduct heat from the first heat transfer element; when an accident occurs in the lunar reactor, as the core temperature rises, the second heat transfer element passively activates to conduct heat from the first heat transfer element to the outside.

[0008] The passive residual heat removal system provided in the embodiments of this application provides a first heat transfer element, which is thermally connected to each core heat transfer element. This ensures that even if individual thermoelectric conversion elements fail, the core heat transfer elements connected to the failed thermoelectric conversion elements can still transfer heat from the core to other normally functioning thermoelectric conversion elements through the first heat transfer element, thereby preventing a significant increase in core temperature and improving the reliability of the lunar reactor.

[0009] The passive residual heat removal system provided in the embodiments of this application includes a second heat transfer element, which is configured not to transfer heat during normal operation of the lunar reactor. In the event of an accident at the lunar reactor, as the core temperature rises, the heat from the first heat transfer element is conducted to the outside. Thus, when the lunar reactor is operating normally, the heat from the core is prevented from diffusing outward through the second heat transfer element, thereby having almost no impact on the thermoelectric conversion efficiency of the lunar reactor. In the event of an accident at the lunar reactor, the core heat transfer element fails, causing the core temperature to rise. As the core temperature rises, the second heat transfer element is passively activated, allowing the residual heat from the core to be conducted to the outside through the core heat transfer element, the first heat transfer element, and the second heat transfer element, thereby ensuring that the core temperature does not rise significantly and a meltdown accident does not occur.

[0010] Secondly, embodiments of this application also provide a lunar reactor that includes the passive waste heat removal system provided in the embodiments of the first aspect of this application. Attached Figure Description

[0011] Other objects and advantages of this application will become apparent from the following description of embodiments of this application with reference to the accompanying drawings, and will help to provide a comprehensive understanding of this application.

[0012] Figure 1 This is a schematic diagram of the structure of the lunar stack provided in an embodiment of this application.

[0013] Figure 2 yes Figure 1 The diagram shows a cross-section of the lunar surface pile.

[0014] Figure 3 This is a schematic diagram of a passive waste heat removal system for lunar reactors provided in an embodiment of this application.

[0015] Figure 4 yes Figure 3 The diagram shows a cross-sectional view of the passive waste heat removal system.

[0016] Figure 5 This is a cross-sectional view of the core of the lunar reactor provided in an embodiment of this application.

[0017] Figure 6 This is a cross-sectional view of the lunar surface stack after it has been installed in the lunar crater, as provided in an embodiment of this application.

[0018] Explanation of reference numerals in the attached figures:

[0019] 100. Passive waste heat removal system;

[0020] 10. First heat transfer element; 1001. First sealed space; 11. First shell; 111. First cylindrical component; 112. First cover; 1121. Through hole; 113. Pipe fitting; 20. Second heat transfer element; 2001. Second sealed space; 21. Second shell; 211. Second cylindrical component; 212. Second cover;

[0021] 200. Lunar stack;

[0022] 201. Core; 2011. Lump fuel; 2012. Radial reflector layer; 202. Core heat transfer components; 2021. First tube section; 2022. Second tube section; 2023. Third tube section; 203. Thermoelectric conversion element; 204. Shielding; 205. Vibration damping device;

[0023] 300. Moon surface; 301. Moon crater.

[0024] It should be noted that the accompanying drawings are not necessarily drawn to scale, but are shown only in a schematic manner without affecting the reader's understanding. Detailed Implementation

[0025] Exemplary embodiments of this application will be described below with reference to the accompanying drawings. For clarity and brevity, not all features of actual implementations are described in the specification. However, it should be understood that many implementation-specific decisions must be made in the development of any such actual embodiment to achieve the developer's specific goals, such as complying with constraints related to the system and business, and these constraints may vary depending on the implementation. Furthermore, it should be understood that while development work can be very complex and time-consuming, such development work is merely a routine task for those skilled in the art who benefit from the content of this application.

[0026] It should also be noted that, in order to avoid obscuring this application with unnecessary details, only the equipment structure and / or processing steps closely related to the solution according to this application are shown in the accompanying drawings, while other details that are not closely related to this application are omitted.

[0027] Ground-based nuclear reactors typically have residual heat removal systems to dissipate residual heat after an accident and reactor shutdown. These systems usually remove residual heat by injecting water into the reactor or by ventilating it. However, for lunar reactors, which require launch to the lunar surface for deployment, ground-based residual heat removal systems are unsuitable for lunar deployment.

[0028] To address the aforementioned issues, embodiments of this application provide a passive waste heat removal system suitable for lunar reactors, as well as a lunar reactor itself.

[0029] Embodiments of this application provide a passive residual heat removal system suitable for lunar reactors, see [link to relevant documentation]. Figure 1 , Figure 1 This is a schematic diagram of the structure of a lunar reactor 200 provided in an embodiment of this application. The lunar reactor 200 includes a reactor core 201, at least one core heat transfer element 202, and at least one thermoelectric conversion element 203 disposed outside the reactor core 201. The reactor core 201 is used to provide heat, the core heat transfer element 202 is used to conduct the heat of the reactor core 201 to the corresponding thermoelectric conversion element 203, and the thermoelectric conversion element 203 is used to convert the heat of the reactor core 201 into electrical energy.

[0030] See Figure 1 and Figure 2 , Figure 2 yes Figure 1 The cross-sectional view of the lunar reactor 200 shown indicates that the passive residual heat removal system 100 may include a first heat transfer element 10 and a second heat transfer element 20. The first heat transfer element 10 is disposed outside the reactor core 201 and is thermally connected to each reactor core heat transfer element 202. The second heat transfer element 20 is thermally connected to the first heat transfer element 10 and is configured such that: when the lunar reactor 200 is operating normally, the second heat transfer element 20 does not conduct heat from the first heat transfer element 10; when an accident occurs in the lunar reactor 200, as the temperature of the reactor core 201 rises, the second heat transfer element 20 passively activates to conduct heat from the first heat transfer element 10 to the outside.

[0031] The passive waste heat removal system 100 provided in the embodiments of this application provides a first heat transfer element 10, which is thermally connected to each core heat transfer element 202. This ensures that even if individual thermoelectric conversion elements 203 are damaged, the core heat transfer elements 202 connected to the damaged thermoelectric conversion elements 203 can still transfer the heat from the core 201 to other normally functioning thermoelectric conversion elements 203 through the first heat transfer element 10, thereby preventing a significant increase in the temperature of the core 201 and improving the reliability of the lunar reactor 200.

[0032] The passive residual heat removal system 100 provided in the embodiments of this application is configured with a second heat transfer element 20, which is set to not transfer heat when the lunar reactor 200 is operating normally. When an accident occurs in the lunar reactor 200, as the temperature of the core 201 rises, the heat of the first heat transfer element 10 can be conducted to the outside. Thus, when the lunar reactor 200 is operating normally, the heat of the core 201 can be prevented from diffusing outward through the second heat transfer element 20, thereby having almost no impact on the thermoelectric conversion efficiency of the lunar reactor 200. When an accident occurs in the lunar reactor 200, the core heat transfer element 202 fails, causing the temperature of the core 201 to rise. As the temperature of the core 201 rises, the second heat transfer element 20 is passively activated, allowing the residual heat of the core 201 to be conducted to the outside through the core heat transfer element 202, the first heat transfer element 10, and the second heat transfer element 20, thereby ensuring that the temperature of the core 201 does not rise significantly and a meltdown accident occurs.

[0033] In some embodiments, the second heat transfer element 20 is a shaped heat pipe, and the minimum start-up temperature of the second heat transfer element 20 is higher than the temperature of the first heat transfer element 10 when the lunar reactor 200 is operating normally. In such an embodiment, when the lunar reactor 200 is operating normally, since the temperature of the first heat transfer element 10 is lower than the minimum start-up temperature of the second heat transfer element 20, the second heat transfer element 20 does not start, that is, the second working medium within the second heat transfer element 20 does not undergo a phase change, and its thermal conductivity is negligible; the heat generated by the reactor core 201 is not wasted by transferring it to the outside through the second heat transfer element 20, thus avoiding affecting the thermoelectric conversion efficiency of the lunar reactor 200. When the lunar reactor 200 experiences an accident, as the temperature of the reactor core 201 rises to the minimum start-up temperature of the second heat transfer element 20, the second working medium within the second heat transfer element 20 undergoes a phase change for efficient heat transfer, which can quickly transfer the heat of the reactor core 201 to the outside.

[0034] In some embodiments, both the second heat transfer element 20 and the first heat transfer element 10 are irregularly shaped heat pipes, and the minimum start-up temperature of the second heat transfer element 20 is higher than that of the first heat transfer element 10. In such an embodiment, during normal operation of the lunar reactor 200, by setting the temperature of the reactor core 201 to be higher than the minimum start-up temperature of the first heat transfer element 10 and lower than the minimum start-up temperature of the second heat transfer element 20, the heat of the reactor core 201 can be transferred to the thermoelectric conversion element 203 and the first heat transfer element 10 through the reactor core heat transfer element 202, but the heat of the reactor core 201 will not be transferred to the outside through the second heat transfer element 20, thereby reducing the heat loss of the reactor core 201.

[0035] See Figure 2 , Figure 3 and Figure 4 , Figure 3 This is a schematic diagram of the structure of a passive waste heat removal system 100 applicable to a lunar reactor 200 provided in an embodiment of this application. Figure 4yes Figure 3 The cross-sectional view of the passive waste heat removal system 100 shown illustrates that, in some embodiments, the first heat transfer element 10 includes a first shell 11 for forming a first sealed space 1001 and a first heat transfer medium disposed within the first sealed space 1001 for heat transfer via phase change. The first shell 11 includes a first cylindrical member 111, two first cover members 112 for closing both ends of the first cylindrical member 111 and having multiple through holes 1121, and multiple pipes 113 connecting the peripheries of the corresponding through holes 1121 of the two first cover members 112. The first cylindrical member 111, the two first cover members 112, and the multiple pipes 113 together form the first sealed space 1001. Each core heat transfer element 202 passes through the pipes 113 and is thermally connected to a corresponding thermoelectric conversion element 203. The core heat transfer element 202 is thermally connected to the pipes 113. In such an embodiment, each core heat transfer element 202 can be thermally connected to the first cylinder 111 through the pipe 113. The heat of the core heat transfer element 202 is transferred to the first heat transfer medium, and the first heat transfer medium undergoes phase change heat transfer, so that the first heat transfer element 10 is in a thermally conductive state.

[0036] In some embodiments, each fitting 113 is welded to the periphery of the corresponding through hole 1121 to enhance heat conduction.

[0037] See Figure 2 , Figure 3 and Figure 4 In some embodiments, the second heat transfer element 20 includes: a second shell 21 for forming a second sealed space 2001 and a second heat transfer medium disposed within the second sealed space 2001 for heat transfer via phase change; wherein, the second shell 21 includes a second cylinder 211 disposed radially outside the first cylinder 111, and two second covers 212 for closing the annular space between the second cylinder 211 and the first cylinder 111, the second cylinder 211, the two second covers 212, and the first cylinder 111 together form the second sealed space 2001. In such embodiments, the second heat transfer medium is thermally connected to the first heat transfer medium through the first cylinder 111, resulting in high thermal conductivity and facilitating the second heat transfer element 20 to reach the minimum start-up temperature of the second heat transfer medium.

[0038] In such an embodiment, when the second heat transfer element 20 transfers heat, heat is transferred from the first cylinder 111 to the second cylinder 211. Since the second cylinder 211 has a large area, it is beneficial to increase the radiative heat dissipation area and improve the heat dissipation effect.

[0039] In some embodiments, the second heat transfer element 20 may be configured to satisfy the following conditions: when the residual heat of the core 201 is discharged using the second heat transfer element 20, the temperature of the second cylinder 211 of the second heat transfer element 20 is higher than the minimum start-up temperature of the second heat transfer medium, and the heat of the core 201 can be discharged so that the temperature of the core 201 is lower than its melting point.

[0040] In some embodiments, the surface area of ​​the second cylinder 211 can be determined using the radiative heat transfer formula based on the above conditions.

[0041] In some embodiments, the radial outer surface of the second cylinder 211 is provided with a high emissivity coating. In such embodiments, this arrangement is beneficial for increasing the rate at which the second cylinder 211 conducts heat to the outside, thereby accelerating the rate at which residual heat is removed from the lunar reactor 200.

[0042] High emissivity coatings have high infrared emissivity, for example, infrared emissivity > 0.85.

[0043] In some embodiments, the radial inner and radial outer surfaces of the first cylinder 111, the inner surface of the first cover 112, the radial outer surface of the pipe 113, the radial inner surface of the second cylinder 211, and the inner surface of the second cover 212 are all provided with liquid-absorbing cores to accelerate the heat transfer rate of the first heat transfer medium and the second heat transfer medium.

[0044] In some embodiments, the outer surfaces of the first cover 112 and the second cover 212 are provided with an insulation layer to reduce heat diffusion from the first cover 112 and the second cover 212 to the outside. In such embodiments, during normal operation of the lunar reactor 200, the reduction of heat diffusion from the first cover 112 and the second cover 212 to the outside by the above-mentioned arrangement can reduce the heat loss of the reactor core 201, thereby avoiding affecting the thermoelectric conversion efficiency of the lunar reactor 200.

[0045] In some embodiments, the insulation layer is a multilayer metal foil to provide better insulation performance.

[0046] In some embodiments, the first cylinder 111, the first cover 112, the tube 113, the second cylinder 211, and the second cover 212 may be made of Ni-Cr based solid solution strengthened wrought superalloy (Haynes 230).

[0047] In some embodiments, when both the first heat transfer element 10 and the second heat transfer element 20 are irregularly shaped heat pipes, the first heat transfer medium of the first heat transfer element 10 can be sodium, and the second heat transfer medium of the second heat transfer element 20 can be lithium. That is, the first heat transfer element 10 can be an irregularly shaped sodium heat pipe, and the second heat transfer element 20 can be an irregularly shaped lithium heat pipe.

[0048] In some embodiments, the core heat transfer element 202 may be a heat pipe. The heat transfer medium of the core heat transfer element 202 may be the same as the first heat transfer medium of the first heat transfer element 10. For example, the core heat transfer element 202 may be a sodium heat pipe.

[0049] In some embodiments, the core 201 temperature of the lunar reactor 200 is 788-820°C, the minimum start-up temperature of the first heat transfer element 10 and the core heat transfer element 202 is set to 540-550°C, and the minimum start-up temperature of the second heat transfer element 20 is set to 840-850°C. This setting is beneficial to improving the thermoelectric conversion efficiency while ensuring the safety of the core 201.

[0050] Embodiments of this application also provide a lunar stack 200, which includes the passive waste heat removal system 100 provided in any embodiment of this application.

[0051] See Figure 2 and Figure 5 , Figure 5 This is a cross-sectional view of the core 201 of a lunar reactor 200 provided in an embodiment of this application. In some embodiments, the core 201 may include block fuel 2011 and a radial reflective layer 2012 disposed radially outside the block fuel 2011. The block fuel 2011 forms a plurality of fuel channels, and there are a plurality of core heat transfer elements 202, each extending through a corresponding fuel channel to the outside of the core 201. In such an embodiment, the core heat transfer elements 202 extending through the corresponding fuel channels formed by the block fuel 2011 to the outside of the core 201 facilitates the transfer of heat from the block fuel 2011 to the thermoelectric conversion element 203.

[0052] In some embodiments, the block fuel 2011 may be a uranium-molybdenum alloy.

[0053] In some embodiments, the thermoelectric conversion element 203 may be a free-piston Stirling generator. In some embodiments, when the thermoelectric conversion element 203 is a free-piston Stirling generator, the lunar stack 200 may further include a vibration damping device 205 for reducing the vibration of the free-piston Stirling generator during the process of converting heat into electrical energy.

[0054] See Figure 2 and Figure 5In some embodiments, the lunar reactor 200 may further include a shield 204 disposed between the reactor core 201 and the thermoelectric conversion element 203, for providing shielding for the thermoelectric conversion element 203; a core heat transfer element 202 passes through the shield 204; a first heat transfer element 10 is thermally connected to the core heat transfer element 202 above the shield 204, and a second heat transfer element 20 is thermally connected to the first heat transfer element 10 above the shield 204. In such embodiments, the shield 204 can shield radiation rays from the reactor core 201 to prevent the radiation rays from the reactor core 201 from affecting the thermoelectric conversion element 203.

[0055] In some embodiments, the core heat transfer element 202 may include a first tube segment 2021, a second tube segment 2022, and a third tube segment 2023 thermally connected to the thermoelectric conversion element 203; wherein the second tube segment 2022 extends radially outward and upward from the upper end of the first tube segment 2021 to the lower end of the third tube segment 2023. In such an embodiment, the above arrangement ensures that even if radiation rays from the core 201 can penetrate the shield 204 through the first tube segment 2021 of the core heat transfer element 202, they cannot reach the thermoelectric conversion element 203 through the second tube segment 2022 and the third tube segment 2023, thereby preventing radiation rays from the core 201 from affecting the thermoelectric conversion element 203.

[0056] See Figure 2 In some embodiments, the first pipe segment 2021, the second pipe segment 2022, and the third pipe segment 2023 of the core heat transfer element 202 can all be straight pipe segments, which are connected by elbows. In some embodiments, the first pipe segment 2021 of each core heat transfer element 202 extends through a corresponding fuel passage and the shield 204 to the top of the shield 204.

[0057] See Figure 6 , Figure 6 This is a cross-sectional view of the lunar reactor 200 installed in a lunar crater according to an embodiment of this application. When the lunar reactor 200 is arranged on the lunar surface 300, a lunar crater 301 can be formed on the lunar surface 300, and the shield 204 and the reactor core 201 are jointly disposed in the lunar crater 301. The first heat transfer element 10 is thermally connected to the reactor core heat transfer element 202 above the shield 204, and the second heat transfer element 20 is thermally connected to the first heat transfer element 10 above the shield 204, so that the passive residual heat removal system 100 can be disposed above the lunar crater 301, thereby facilitating heat conduction to the outside.

[0058] The working process of the lunar stack 200 provided in the embodiments of this application will be described in detail below with reference to specific embodiments.

[0059] After the lunar stack 200 is successfully deployed on the lunar surface 300, the position of the safety rod (not shown in the figure) is adjusted by the safety rod drive mechanism (not shown in the figure) until the entire lunar stack 200 reaches the rated power stable operation state.

[0060] When the lunar reactor 200 is operating normally, the temperature of the bulk fuel 2011 is 800°C, and the temperature of the core heat transfer element 202 (i.e., sodium heat pipe) is 780°C. The core heat transfer element 202 transfers the heat from the core 201 to the Stirling generator 203, thereby generating electricity. At this time, since the minimum start-up temperature of the second heat transfer element 20 (i.e., shaped lithium heat pipe) is higher than the temperature of the core heat transfer element 202, only a very small amount of heat from the core heat transfer element 202 is conducted through the first heat transfer element 10 (i.e., shaped sodium heat pipe) and the first cylindrical section 111 of the first heat transfer element 10 to the radial outer surface of the second heat transfer element 20 (i.e., the second cylindrical section 211), which hardly causes a decrease in the thermoelectric conversion efficiency of the lunar reactor 200.

[0061] When one or more Stirling generators 203 fail, the core heat transfer components 202 that are thermally connected to the failed Stirling generator 203 can still continue to operate. These core heat transfer components 202 can conduct the heat from the core 201 to the remaining core heat transfer components 202 through the first heat transfer component 10, and finally to the remaining normally operating Stirling generators 203. Therefore, the temperature of the core 201 will not rise significantly, and the passive residual heat removal system 100 significantly improves the reliability of the entire lunar reactor 200.

[0062] When lunar reactor 200 experiences an accident and shuts down, in the worst-case scenario, such as when all Stirling generators 203 fail and cannot remove heat from the core 201, residual core heat can still be discharged through the core heat transfer element 202 and the passive residual heat removal system 100. Initially, the core heat transfer element 202 operates at approximately 780°C. At this point, the second heat transfer element 20 is not operational, and the passive residual heat removal system 100 is also unable to effectively remove core heat power. Due to the presence of residual heat in the core 201 (such as the decay heat of fission products), the temperature of the lumpy fuel 2011 will rise, and the temperatures of the core heat transfer element 202 and the first heat transfer element 10 will also rise accordingly. When the temperature of the first heat transfer element 10 rises to the minimum start-up temperature of the second heat transfer element 20 (850°C), the second heat transfer element 20 will start operation and begin heat transfer. At this time, the thermal power of the lumpy fuel 2011 can be efficiently transferred to the radial outer wall of the second heat transfer element 20 through the core heat transfer element 202, the first heat transfer element 10, and the second heat transfer element 20, and then discharged through radiative heat dissipation, thereby ensuring that the lumpy fuel 2011 will not melt down.

[0063] Regarding the embodiments of this application, it should also be noted that, without conflict, the embodiments of this application and the features in the embodiments can be combined with each other to obtain new embodiments.

[0064] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. The scope of protection of this application shall be determined by the scope of the claims.

Claims

1. A passive waste heat removal system suitable for a lunar reactor, the lunar reactor comprising a core, at least one core heat transfer element, and at least one thermoelectric conversion element disposed outside the core, wherein, The reactor core is used to provide heat, the reactor core heat transfer element is used to conduct the heat of the reactor core to the corresponding thermoelectric conversion element, and the thermoelectric conversion element is used to convert the heat of the reactor core into electrical energy. The passive waste heat removal system is characterized by comprising: The first heat transfer element is disposed on the outside of the core and is used for thermally conductive connection with each of the core heat transfer elements; The second heat transfer element is used to thermally connect with the first heat transfer element. The second heat transfer element is configured such that: when the lunar reactor is operating normally, the second heat transfer element does not conduct heat from the first heat transfer element; when the lunar reactor experiences an accident, as the core temperature rises, the second heat transfer element is passively activated to conduct heat from the first heat transfer element to the outside. Both the second heat transfer element and the first heat transfer element are irregularly shaped heat pipes, and the minimum start-up temperature of the second heat transfer element is higher than that of the first heat transfer element. The first heat transfer element includes a first shell for forming a first sealed space and a first heat transfer medium disposed within the first sealed space for heat transfer through phase change. The first shell includes: a first cylindrical member, two first cover members for closing both ends of the first cylindrical member and having multiple through holes, and multiple pipes connecting the periphery of the corresponding through holes of the two first cover members. The first cylindrical member, the two first cover members, and the multiple pipes together form the first sealed space. Each of the core heat transfer elements passes through the tube and is thermally connected to a corresponding thermoelectric conversion element, and the core heat transfer element is thermally connected to the tube; The second heat transfer element includes: a second shell for forming a second sealed space and a second heat transfer medium disposed within the second sealed space for heat transfer through phase change; The second shell includes a second cylindrical member disposed radially outside the first cylindrical member, and two second cover members for sealing the annular space between the second cylindrical member and the first cylindrical member. The second cylindrical member, the two second cover members, and the first cylindrical member together form the second sealed space.

2. The passive waste heat removal system according to claim 1, characterized in that, Liquid-absorbing cores are provided on the radial inner and radial outer surfaces of the first cylindrical component, the inner surface of the first cover, the radial outer surface of the tube, the radial inner surface of the second cylindrical component, and the inner surface of the second cover.

3. The passive waste heat removal system according to claim 1, characterized in that, The first heat transfer medium is sodium, and the second heat transfer medium is lithium.

4. The passive waste heat removal system according to claim 1, characterized in that, The outer surfaces of the first cover and the second cover are provided with a heat insulation layer to reduce the heat diffusion from the first cover and the second cover to the outside.

5. The passive waste heat removal system according to claim 4, characterized in that, The insulation layer is a multi-layer metal foil.

6. The passive waste heat removal system according to claim 1, characterized in that, The radial outer surface of the second cylindrical member is provided with a high emissivity coating.

7. The passive waste heat removal system according to any one of claims 1-6, characterized in that, The heat transfer element in the core is a heat pipe.

8. A lunar stack, characterized in that, The lunar reactor includes a passive waste heat removal system. The reactor comprises a core, at least one core heat transfer element, and at least one thermoelectric conversion element disposed outside the core. The core is used to provide heat, the core heat transfer element is used to conduct the heat of the core to the corresponding thermoelectric conversion element, and the thermoelectric conversion element is used to convert the heat of the core into electrical energy. The passive waste heat removal system includes: The first heat transfer element is disposed on the outside of the core and is used for thermally conductive connection with each of the core heat transfer elements; The second heat transfer element is used to thermally connect with the first heat transfer element. The second heat transfer element is configured such that: when the lunar reactor is operating normally, the second heat transfer element does not conduct heat from the first heat transfer element; when the lunar reactor experiences an accident, as the core temperature rises, the second heat transfer element is passively activated to conduct heat from the first heat transfer element to the outside. Both the second heat transfer element and the first heat transfer element are irregularly shaped heat pipes, and the minimum start-up temperature of the second heat transfer element is higher than that of the first heat transfer element. The first heat transfer element includes a first shell for forming a first sealed space and a first heat transfer medium disposed within the first sealed space for heat transfer through phase change. The first shell includes: a first cylindrical member, two first cover members for closing both ends of the first cylindrical member and having multiple through holes, and multiple pipes connecting the periphery of the corresponding through holes of the two first cover members. The first cylindrical member, the two first cover members, and the multiple pipes together form the first sealed space. Each of the core heat transfer elements passes through the tube and is thermally connected to a corresponding thermoelectric conversion element, and the core heat transfer element is thermally connected to the tube; The second heat transfer element includes: a second shell for forming a second sealed space and a second heat transfer medium disposed within the second sealed space for heat transfer through phase change; The second shell includes a second cylindrical member disposed radially outside the first cylindrical member, and two second cover members for sealing the annular space between the second cylindrical member and the first cylindrical member. The second cylindrical member, the two second cover members, and the first cylindrical member together form the second sealed space.

9. The lunar stack according to claim 8, characterized in that, Liquid-absorbing cores are provided on the radial inner and radial outer surfaces of the first cylindrical component, the inner surface of the first cover, the radial outer surface of the tube, the radial inner surface of the second cylindrical component, and the inner surface of the second cover.

10. The lunar stack according to claim 8, characterized in that, The first heat transfer medium is sodium, and the second heat transfer medium is lithium.

11. The lunar stack according to claim 8, characterized in that, The outer surfaces of the first cover and the second cover are provided with a heat insulation layer to reduce the heat diffusion from the first cover and the second cover to the outside.

12. The lunar stack according to claim 11, characterized in that, The insulation layer is a multi-layer metal foil.

13. The lunar stack according to claim 8, characterized in that, The radial outer surface of the second cylindrical member is provided with a high emissivity coating.

14. The lunar stack according to any one of claims 8-13, characterized in that, The heat transfer element in the core is a heat pipe.

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