Hexagonal annular heat pipe cooling reactor

Abstract

The invention belongs to the technical field of heat pipe reactors, and discloses a hexagonal annular heat pipe cooling reactor, which comprises a pipe wall of a heat pipe, a silk screen wick, a steam cavity structure of the heat pipe, uranium-molybdenum alloy fuel, an outer pipe wall of the heat pipe, a wick attached to the inner wall surface of the heat pipe, and uranium-molybdenum alloy. The device is formed by coupling a hexagonal annular heat pipe with a hexagonal fuel element. Firstly, in the aspect of the structure, a framework structure composed of graphite is not needed to fix the heat pipe and the fuel element, an assembly composed of the heat pipe and the fuel element can be directly adopted for expansion to form the fuel element, and gap thermal resistance brought by the framework is eliminated. In addition, in terms of heat transfer performance, the heat transfer performance of the hexagonal annular heat pipe is superior to that of a traditional cylindrical heat pipe. The same heat transfer area is adopted, and under the condition of the same heat transfer power, the temperature of the outer surface of the pipe wall of the hexagonal annular heat pipe is lower than that of a cylindrical heat pipe. Therefore, the material stress requirement in the heat pipe pile and the thermoelectric conversion form of the condensation section can be richer.

Description

Technical Field

[0001] The present invention belongs to, but is not limited to, the technical field of heat pipe reactors, and particularly relates to a hexagonal annular heat pipe cooled reactor. Background Art

[0002] Since the heat pipe was proposed in 1942, it has been widely used in aspects such as space fission nuclear reactors, radiation radiators, heat storage and heat transfer in solar power plants, and modern electronic devices due to its high heat transfer performance, passive heat transfer and other characteristics. The structure of the heat pipe has also evolved from the initial cylindrical capillary heat pipe to diverse heat pipes with different shapes, different working fluids, and different reflux principles.

[0003] With the advancement of deep space and deep sea exploration missions, energy systems represented by nuclear energy have become an inevitable choice for current development due to their good environmental adaptability, long endurance, high power density and other advantages. The heat pipe cooled reactor is a new type of reactor that transfers the heat of the reactor core to the thermoelectric conversion device through high-temperature heat pipes, and has received extensive attention due to its inherent safety attributes, simple structure, and easy modular transportation and expansion.

[0004] Currently, the designs for heat pipe reactors mostly originate from traditional pressurized water reactors. Its main design structure consists of six cylindrical fuel elements evenly surrounding a cylindrical heat pipe, and the skeleton structure uses graphite material. Radially, the presence of the skeleton structure causes an obvious gap thermal resistance between the heat pipe and the fuel element, which is not conducive to the heat dissipation of the fuel element and will also affect the operating temperature of the heat pipe. In addition, flat low- and medium-temperature heat pipes have been widely used in electronic components due to their large contact area and better heat transfer performance, and are rarely mentioned in high-temperature heat pipe cooled reactors. Summary of the Invention

[0005] Aiming at the problems existing in the prior art, the present invention provides a hexagonal annular heat pipe cooled reactor. The present invention is implemented as follows. A hexagonal annular heat pipe cooled reactor, the device includes:

[0006] The tube wall of the heat pipe, the wire mesh wick, the steam cavity structure of the heat pipe, the uranium-molybdenum alloy fuel, the wick attached to one side of the inner wall surface of the heat pipe, and the other side is in contact with the uranium-molybdenum alloy fuel element.

[0007] Further, the tube wall of the heat pipe adopts a 316 stainless steel structure; the wire mesh wick adopts a stainless steel wire mesh with a mesh count of 200 to 400 meshes.

[0008] Further, the steam cavity structure of the heat pipe provides a steam flow path.

[0009] Furthermore, the wick attached to the inner wall surface of the heat pipe generally adopts a wire mesh structure, and the wire mesh is tightly attached to the inner surface of the pipe wall through spot welding technology. This structure is compared with the conventional one.

[0010] Furthermore, as a fuel, the uranium-molybdenum alloy has a significantly improved thermal conductivity compared with the traditional uranium dioxide. The metal uranium-molybdenum alloy helps to quickly conduct the heat from the reactor core and improve the power density. The uranium atomic density of the metal fuel is high, which is suitable for miniaturized design and applicable to the space nuclear power source scenario.

[0011] Furthermore, the hexagonal annular heat pipe is composed of two concentric regular hexagonal stainless steel plates. The two ends of the steel plates are welded with hexagonal rings to form a hollow annular hexagonal prism. The wire mesh wick is welded to the inner surface of the heat pipe wall by spot welding technology. The working fluid in the heat pipe is heated by the fission heat of the reactor core in the evaporation section and then evaporates. Subsequently, the gaseous working fluid gathered in the evaporation section moves from the evaporation section to the condensation section under the action of the pressure difference, liquefies in the condensation section and releases the latent heat, which is transferred to the thermoelectric conversion device through the heat conduction of the pipe wall. The liquefied working fluid flows back to the evaporation section under the action of the capillary force of the wick and is heated again. This cycle forms a passive cycle. The working fluid used is sodium. During the actual operation of the sodium heat pipe, its operating temperature ranges from 600 to 800 °C. In this temperature range, the pressure range of the saturated sodium vapor is from 3260 to 45390 Pa.

[0012] Combined with the above technical solutions and the technical problems solved, the advantages and positive effects of the technical solution to be protected by the present invention are as follows:

[0013] First, aiming at the gap thermal resistance existing in the current heat pipe reactor design, which affects the heat pipe efficiency, the present invention adopts a combination of a hexagonal annular heat pipe and a hexagonal fuel element.

[0014] First of all, in terms of structure, there is no need for a skeleton structure composed of graphite to fix the heat pipe and the fuel element. It can be directly formed by expanding the assembly composed of the heat pipe and the fuel element, eliminating the gap thermal resistance brought by the skeleton. In addition, in terms of heat transfer performance, the heat transfer performance of the hexagonal annular heat pipe is better than that of the traditional cylindrical heat pipe. With the same heat transfer area and under the same heat transfer power condition, the outer surface temperature of the wall of the hexagonal annular heat pipe is lower than that of the cylindrical heat pipe. This reduces the strength requirements for the internal materials of the heat pipe reactor.

[0015] Second, compared with the traditional heat pipe reactor design, the new design reduces the temperature difference between the fuel pellet and the heat pipe, increases the operating temperature of the heat pipe in the heat pipe reactor, and can effectively improve the heat transfer efficiency of the heat pipe. The improvement of the heat transfer efficiency of the heat pipe can effectively improve the thermal efficiency of the whole reactor, promoting the development of the heat pipe reactor towards a more miniaturized, structurally compact and high-economic direction. It can effectively reduce the size and reduce the load of aerospace equipment and deep-sea exploration equipment, improving the economy.

[0016] Thirdly, compared with the traditional design of inserting fuel elements and heat pipes alternately into the matrix structure of "honeycomb coal", the honeycomb coal structure has inherent problems such as difficulty in machining high-precision deep holes and difficulty in precision assembly with heat pipes and fuel elements. This design uses a single-module assembly combining special-shaped heat pipes and hexagonal fuel elements to form a core module. Reducing the difficulty of manufacturing and assembling the structure from the order of hundreds of components to only focusing on a single component is beneficial to improving engineering feasibility, and is also beneficial to manufacturing quality control and reliability improvement.

[0017] The optimization of the heat pipe configuration in the present invention is the first time. It breaks away from the inherent thinking of traditional reactor rod-type fuels and comes from the combination of the optimized design of plate-type fuels and the innovative optimization of flat heat pipes, overcoming the common problem of gap thermal resistance in reactors. Using the design principle of a honeycomb, a skeleton structure is not required.

[0018] Most importantly, the present invention applies the hexagonal ring heat pipe to the design of a heat pipe reactor for the first time, overcoming the inherent thinking of the common cylindrical heat pipes in the design of heat pipe reactors. It is the first time both in terms of performance and in the design concept of heat pipe reactors. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a cross-sectional schematic diagram of a hexagonal ring heat pipe and a hexagonal fuel element provided by an embodiment of the present invention.

[0020] Figure 2 is a combined element of a single heat pipe and fuel provided by an embodiment of the present invention.

[0021] Figure 3 is the steam temperature that can be obtained from a traditional cylindrical heat pipe and a hexagonal ring heat pipe with the same flow area and the same length provided by an embodiment of the present invention.

[0022] Figure 4 is a schematic diagram of a heat pipe reactor, where Figure 4 (a) represents the layout of a traditional heat pipe reactor, the gray circles represent fuel rods, and the white circles represent heat pipes. Six fuel rods are evenly arranged around one heat pipe. The area surrounded by the dotted line refers to an effective unit. Figure 4 (b) represents the heat pipe reactor unit of the present invention, and the specific details are as Figure 1 shown.

[0023] Figure 5 is a schematic diagram of the simulated temperature of a heat pipe reactor. Among them, Figure 5 (a) represents the design of a traditional heat pipe reactor, Figure 5 (b) represents the design of the heat pipe reactor of the present invention. The effective units of the two designs ensure the same fuel power, the same volume, and the same heat pipe flow area.

[0024] In the figure: 1. The tube wall of the heat pipe; 2. The wire mesh wick; 3. The steam cavity structure of the heat pipe; 4. The uranium-molybdenum alloy fuel; 5. The outer tube wall of the heat pipe; 6. The wick attached to the inner wall surface of the heat pipe; 7. The uranium-molybdenum alloy. Specific embodiments

[0025] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below in conjunction with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0026] An embodiment of the present invention provides a hexagonal annular heat pipe cooled reactor, and the device includes:

[0027] The tube wall 1 of the heat pipe, the wire mesh wick 2, the steam cavity structure 3 of the heat pipe, the uranium-molybdenum alloy fuel 4, the outer tube wall 5 of the heat pipe, the wick 6 attached to the inner wall surface of the heat pipe, and the uranium-molybdenum alloy 7.

[0028] The tube wall 1 of the heat pipe is made of 316 stainless steel structure; the wire mesh wick 2 is made of copper wire mesh with a mesh number of 200 to 400 meshes.

[0029] The steam cavity 3 structure of the heat pipe provides a steam flow path.

[0030] The wick 6 attached to the inner wall surface of the heat pipe generally adopts a wire mesh structure, and the wire mesh is closely attached to the inner surface of the tube wall by spot welding technology.

[0031] As a fuel, the uranium-molybdenum alloy 7 has a significantly improved thermal conductivity compared with traditional uranium dioxide. The uranium-molybdenum alloy helps to quickly conduct the heat of the reactor core and improve the power density; the uranium atomic density of the metal fuel is high, which is suitable for miniaturized design and is applicable to the scenario of space nuclear power supply.

[0032] The hexagonal annular heat pipe cooled reactor of the present invention uses an efficient heat pipe as a cooling medium to ensure efficient thermal management of a high power density reactor. The tube wall 1 of the heat pipe is made of 316 stainless steel structure, which not only has good corrosion resistance and high temperature stability, but also ensures the long-term reliable operation of the system under extreme conditions. The steam cavity structure 3 inside the heat pipe is responsible for providing a flow path for the working fluid steam. In the hot end region (nuclear fuel heating section), the working fluid evaporates, absorbs heat and conveys the heat to the cold end, realizing efficient heat transfer.

[0033] The wick 6 of the heat pipe adopts a wire mesh structure and is closely attached to the inner surface of the pipe wall by spot welding technology, thus forming a stable capillary action channel. The wire mesh wick 2 is made of a stainless steel wire mesh with a mesh size of 200 to 400 meshes, and its fine mesh structure ensures that the working fluid in the condensation section can quickly flow back to the evaporation end. The capillary force-driven backflow of the working fluid does not require a mechanical pump, improving the reliability of the system and making it suitable for unattended space nuclear power applications.

[0034] The uranium-molybdenum alloy fuels 4 and 7 used in the present invention have higher thermal conductivity and uranium atom density compared to the traditional uranium dioxide (UO2) fuel. The high thermal conductivity of the uranium-molybdenum alloy ensures that the heat released by the fission reaction can be quickly transferred to the evaporation end of the heat pipe, effectively reducing the risk of local overheating in the reactor core and increasing the reactor power density. At the same time, the high uranium density of the uranium-molybdenum alloy enables the reactor to provide a higher power output in a smaller volume, which is crucial for applications such as space nuclear power, lunar bases, and small portable nuclear reactors.

[0035] The design of the hexagonal ring structure enables multiple heat pipes to be arranged efficiently, forming a ring-shaped cooling channel and enhancing the heat management ability. The outer pipe wall 5 of the heat pipe provides structural support and ensures the close coupling of the fuel and the cooling system. During the operation of the entire system, the heat released by the fission reaction is transferred from the fuel to the heat pipe wall, and then the working fluid evaporates inside the evaporation chamber 3 and transfers heat to the condensation end. Finally, the heat is discharged to the environment or other working fluids through radiation or a heat exchange system, realizing efficient energy conversion with passive cooling. This design not only improves the overall heat dissipation efficiency of the reactor but also reduces the dependence on the active cooling system, making it more suitable for long-term operation in extreme environments.

[0036] The hexagonal annular heat pipe is composed of two concentric equilateral hexagonal stainless steel plates. The two ends of the steel plates are welded with hexagonal rings to form a hollow annular hexagonal prism; the wire mesh wick is welded to the inner surface of the heat pipe wall by spot welding technology; the working fluid inside the heat pipe evaporates when heated by the fission heat in the evaporation section, and then the gaseous working fluid aggregated in the evaporation section moves from the evaporation section to the condensation section under the action of the pressure difference, liquefies in the condensation section and releases heat to the thermoelectric conversion device; the liquefied working fluid flows back to the evaporation section under the capillary force of the wick and is heated again to form the entire cycle; the working fluid used is sodium metal, and during the actual operation of the sodium heat pipe, its operating temperature ranges from 600 to 800 °C; within this temperature range, the pressure range of the saturated sodium vapor is from 3260 to 45390 Pa.

[0037] As an energy supply device, the effective electric power of the present invention ranges from 0.1 MW to 10 MW. It can be effectively applied to energy supply for deep space probes, unmanned underwater devices, deep sea exploration devices, as well as islands and remote areas. As a distributed power source, it can also be applied in the field of emergency disaster relief to provide power guarantee for temporary resettlement sites, rescue equipment, and medical facilities.

[0038] Calculating the steam temperature of a traditional cylindrical heat pipe and a hexagonal annular heat pipe with the same flow area and the same length, the results are shown as follows Figure 3 As shown, at the same power, the steam chamber temperature of the hexagonal annular heat pipe is significantly lower than that of the traditional heat pipe. When the power is increased by 160 W, the annular heat pipe is easier to reach stability and the temperature at stability is also lower than that of the traditional heat pipe.

[0039] In addition, compared with the traditional cylindrical heat pipe, the hexagonal annular heat pipe has a larger wick volume. This makes it easier for the condensed liquid to flow back to the evaporation section, improving the capillary limit of the heat pipe.

[0040] During the assembly process of multiple heat pipe elements, the hexagonal annular heat pipe does not require a skeleton for support. Multiple hexagonal annular structures can share a pipe wall, thus greatly reducing the existence of gap thermal resistance.

[0041] The present invention has innovatively optimized the structural design of the heat pipe stack. Compared with the traditional heat pipe stack, its design scheme can effectively reduce the temperature of the fuel element and improve the safety and stability of the system. In the traditional heat pipe stack design ( Figure 4 (a)), a single heat pipe stack unit consists of multiple heat pipes, while the heat pipe stack design of the present invention ( Figure 4 (b)) adopts a complete unit structure, making the heat transfer more uniform and reducing the local overheating problem caused by temperature unevenness. Through this improvement, the present invention achieves a better heat management effect under the same core fuel power.

[0042] The simulation results ( Figure 5 ) show that the heat pipe stack design of the present invention can significantly reduce the maximum temperature of the fuel element. In the traditional design, the maximum temperature of the heat pipe fuel element can reach 970 K, while the present invention reduces the maximum temperature to 958 K by optimizing the heat pipe unit structure, a reduction of 12 K. This temperature drop helps to extend the service life of the fuel element and reduce the potential safety hazards caused by overheating during the operation of the heat pipe stack.

[0043] In addition to reducing the maximum temperature of the fuel element, the heat pipe stack of the present invention also optimizes the distribution of hot spots. The simulation results of the traditional design ( Figure 5 (a)) show that the hot spots are mainly concentrated at the six corners of the hexagonal structure, forming 6 high-temperature regions. This multi-hot spot distribution increases the risk of local overheating. While in the new design of the present invention (Figure 5 (b)), by improving the heat pipe unit structure, the hot spots are concentrated at the center of the unit, and the number of hot spots is reduced from 6 to 1, greatly reducing the risk of local overheating and improving the overall thermal management efficiency and the safety of the reactor core.

[0044] The improvement of the heat pipe reactor of the present invention not only enhances the temperature control ability, but also makes the system operation safer and more stable. Since the hot spot position at the center of the unit is easier to manage, compared with the traditional design, the solution of the present invention is less likely to have safety hazards caused by thermal runaway, which is of great significance for application scenarios such as small modular reactors (SMRs). In addition, the optimized solution can reduce thermal stress, improve material durability, and further enhance the engineering applicability of the heat pipe reactor, making it perform better in application environments with high power density and long-term operation.

[0045] Example 1: Small heat pipe reactor for deep space exploration mission

[0046] In this example, a small heat pipe reactor based on the optimized structure of the present invention is designed and applied to the nuclear power supply system in deep space exploration missions. The heat pipe reactor uses sodium-filled heat pipes as the cooling medium and high-temperature radiation-resistant fuel (such as UN-10% Mo alloy) as the core fuel to ensure stable operation in extreme environments.

[0047] Structure optimization: In this example, an improved heat pipe unit design is adopted. By reducing the number of hot spots and optimizing the heat pipe layout, the maximum temperature of the fuel element is reduced by about 12K, improving the stability of the fuel and reducing local thermal stress.

[0048] Improvement of thermal management efficiency: Simulation calculations show that under the operating condition of a power of 5kWth, the heat pipe reactor of the present invention can improve the heat transfer efficiency by more than 10% compared with the traditional heat pipe reactor, while reducing the risk of local overheating.

[0049] Adaptability to deep space environment: For the vacuum environment, in this example, the coupling method between the cold end of the heat pipe and the radiator is optimized, so that the waste heat can be more effectively radiated into space, improving the stability and service life of the heat pipe.

[0050] The heat pipe reactor can be used as the main energy system of deep space detectors (such as lunar bases, Mars exploration stations), providing long-term and stable nuclear power supply, while reducing maintenance costs and system failure risks.

[0051] Example 2: Compact heat pipe reactor for undersea unmanned nuclear power plant

[0052] This embodiment applies the heat pipe reactor of the present invention to an undersea unmanned nuclear power device (such as a deep-sea detector or an underwater unmanned vehicle UUV) to achieve long-term autonomous power supply. This system adopts liquid metal cooling technology and combines the unitized heat pipe reactor design of the present invention to improve the safety and reliability of the system.

[0053] Temperature control optimization: Due to the high pressure and complex heat conduction characteristics of the deep-sea environment, this embodiment adopts a multi-layer heat pipe heat exchange structure and combines the unit center hot spot design of the present invention to make the temperature control of the core fuel more uniform and effectively avoid damage to the fuel elements caused by thermal stress.

[0054] Improved safety: Traditional undersea nuclear power systems have multiple high-temperature hot spots, which may lead to the risk of cooling failure. The optimized design of the present invention reduces the number of hot spots from 6 to 1, making the heat more concentrated in a controllable area and improving the safety and stability of the system.

[0055] Low-noise operation: This heat pipe reactor adopts a passive cooling method without mechanical moving parts. Compared with traditional reactors, it reduces the energy loss of cooling pumps and mechanical components and reduces noise at the same time, making it more suitable for underwater detection tasks with high concealment.

[0056] Experimental data shows that in the seawater environment at a depth of 500m, the heat pipe reactor of the present invention can operate stably at a power of 40kWth for more than 5 years, and the temperature of the fuel elements always remains within the safe range, greatly improving the application prospect of underwater nuclear power devices.

[0057] The above is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be covered by the protection scope of the present invention.

Claims

1. A hexagonal ring-shaped heat pipe cooled reactor, characterized in that, The device includes the tube wall of the heat pipe, the tube wall of the heat pipe; A wire mesh wick, arranged on the inner side of the tube wall of the heat pipe, is composed of a copper wire mesh, and the mesh number of the copper wire mesh is between 200 meshes and 400 meshes; A steam cavity structure, arranged inside the heat pipe, is used to form a flow channel for the working medium steam; Uranium-molybdenum alloy fuel is placed inside the heat pipe; The outer tube wall of the heat pipe is used to form the peripheral support structure of the heat pipe; On the inner wall surface of the heat pipe, the wire mesh wick is closely attached by spot welding technology; Uranium-molybdenum alloy is arranged inside the reactor.

2. The hexagonal ring-shaped heat pipe cooled reactor according to claim 1, wherein The tube wall of the heat pipe is made of 316 stainless steel material.

3. The hexagonal annular heat pipe cooled reactor according to claim 1, characterized in that, The wire mesh wick adopts a copper wire mesh, and its mesh number is 200 meshes to 400 meshes.

4. The hexagonal annular heat pipe cooled reactor according to claim 1, wherein The steam cavity structure of the heat pipe forms a passage for the circulation of the working medium steam.

5. The hexagonal annular heat pipe cooled reactor according to claim 1, characterized in that, The wick attached to the inner wall surface of the heat pipe adopts a wire mesh structure, and the wire mesh is closely attached to the inner surface of the tube wall by spot welding technology.

6. The hexagonal annular heat pipe cooled reactor according to claim 1, wherein, The hexagonal annular heat pipe is composed of two concentric regular hexagonal stainless steel plates, and its two ends are welded by a hexagonal ring to form a hollow annular hexagonal prism.

7. The hexagonal annular heat pipe cooled reactor according to claim 1, characterized in that, The heat pipe uses metallic sodium as the working medium, and the operating temperature is controlled within the range of 600°C to 800°C. At this temperature, sodium vapor is in a saturated state, and its pressure range is 3260 to 45390 Pa.

8. The hexagonal annular heat pipe cooled reactor according to claim 1, characterized in that, An evaporation section and a condensation section are arranged inside the heat pipe. The working medium evaporates after being heated by fission heat in the evaporation section. The formed gaseous working medium flows from the evaporation section to the condensation section under the action of the pressure difference, liquefies and releases heat in the condensation section, and returns to the evaporation section under the capillary action of the wick to form a cycle.

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