A method of assembling a heat pipe reactor and a heat pipe reactor

Abstract

The application discloses an assembly method of a heat pipe type reactor and the heat pipe type reactor, and belongs to the nuclear power field. The assembly method of the heat pipe type reactor comprises the following steps: closing one end of a mounting hole of a grid base, vertically arranging the grid base so that the closed end is located at the bottom, injecting a filling slurry comprising a heat-conducting powder and a dispersing agent into the mounting hole, subsequently inserting a pipe into the mounting hole until the filling slurry overflows, and uniformly filling the gap between the pipe and the mounting hole in a forced flow mode; and heating to solidify and shape the filling slurry. The method can effectively eliminate the assembly gap between the grid base and the pipe of the heat pipe type reactor, and improve the heat transfer efficiency and the safety margin of the reactor.

Description

Technical Field

[0001] This invention belongs to the field of nuclear power, specifically relating to an assembly method for a heat pipe reactor and the heat pipe reactor itself. Background Technology

[0002] Heat pipe reactors employ an all-solid-state core structure, eliminating the need for a liquid primary loop. Instead, they utilize a solid core to directly transfer heat generated by the fuel rods through contact heat transfer, which is then transported to the power output end via heat pipes. Compared to pressurized water reactors, heat pipe reactors are more compact, inherently safer, and easier to deploy flexibly, thus considered to have promising application prospects. However, the solid-state heat transfer characteristics of heat pipe reactors also place high demands on the assembly precision of their components. Any assembly gaps at the heat transfer interface can increase thermal resistance, impair heat transfer, affect reactor power generation efficiency, and even pose operational risks. Therefore, providing a method to effectively eliminate assembly gaps is of positive significance for improving the safety margin of heat pipe reactors. Summary of the Invention

[0003] The purpose of this invention is to provide an assembly method for a heat pipe reactor that eliminates gaps in the assembly of solid reactor cores. This invention also provides a heat pipe reactor.

[0004] According to one aspect of the present invention, a method for assembling a heat pipe reactor is provided. The heat pipe reactor includes a grid substrate and tubes. The grid substrate includes mounting holes for mounting the tubes. The tubes include heat pipes and fuel rods. Specifically, the method includes the following steps:

[0005] Step a): A plug is provided at one end of the mounting hole of the grid substrate to seal it, and the grid substrate is arranged vertically so that the end with the plug is located at the bottom;

[0006] Step b): Inject a filling slurry into the mounting hole, the filling slurry comprising thermally conductive powder and a dispersant;

[0007] Step c): Insert the pipe fitting along the mounting hole, so that the filling slurry fills the gap between the mounting hole and the pipe fitting and overflows from the top of the mounting hole;

[0008] Step d): Remove the overflowing filler slurry, heat and keep the grid substrate at a certain temperature to solidify the filler slurry.

[0009] The above method can effectively eliminate assembly gaps in solid reactor cores, improve heat transfer efficiency, and the assembly process can be carried out under normal pressure conditions without changing the core structure, making it simple and low-cost.

[0010] Furthermore, in some embodiments, the gap between the mounting hole and the pipe fitting is 50μm-500μm.

[0011] Furthermore, in some embodiments, in step b), the viscosity of the filling slurry is 800 Pa·s-1200 Pa·s, and the yield strength is 180 Pa-230 Pa.

[0012] Furthermore, in some embodiments, in step b), the thermally conductive powder comprises one or a combination of copper powder, iron powder, chromium powder, molybdenum powder, and nickel powder; the dispersant comprises one or a combination of ethanol, ethylene glycol, phosphate, and silicate; and the solid content of the filler slurry is 70%-90%.

[0013] Furthermore, in some embodiments, the heating temperature in step d) does not exceed 850°C.

[0014] Furthermore, in some embodiments, in step d), the heating method is to heat the heat pipe using an external heat source.

[0015] Furthermore, in some embodiments, in step d), the heating method is to directly heat the grid substrate using an electric heating rod.

[0016] Furthermore, in some embodiments, in step d), the heating method is to start the heat pipe reactor and use the fuel rods to heat the grid substrate.

[0017] Furthermore, in some embodiments, step d) further includes a step of using CT to detect the gap filling degree after sintering.

[0018] According to another aspect of the present invention, a heat pipe reactor is provided, comprising a grid substrate, heat pipes and fuel rods, wherein the heat pipe reactor is assembled using the assembly method of the heat pipe reactor provided in any of the foregoing embodiments. Attached Figure Description

[0019] Fig. 1 This is a schematic diagram of step a) in one embodiment;

[0020] Fig. 2 This is a schematic diagram of step b) in one embodiment;

[0021] Fig. 3 This is a schematic diagram of step c) in one embodiment;

[0022] Fig. 4 This is a schematic diagram of step d) in one embodiment.

[0023] Meaning of the reference numerals in the attached figures:

[0024] 1-Grid substrate; 2-Pipe fitting; 3-Mounting hole; 4-Filling slurry; 5-End plug; 6-Cureable filling slurry.

[0025] The purpose of the above-described drawings is to provide a detailed description of the present invention so that those skilled in the art can understand the technical concept of the invention, and is not intended to limit the invention. For the sake of brevity, the above-described drawings only schematically depict the structures related to the technical features of the present invention, and do not depict the complete structure and all details strictly according to actual scale. Detailed Implementation

[0026] The present invention will now be described in further detail with reference to specific embodiments and accompanying drawings.

[0027] The term "embodiment" as used herein means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment herein. The phrase appearing in various places in the specification does not necessarily refer to the same embodiment, nor is it limited to mutually exclusive, independent, or alternative embodiments. Those skilled in the art will understand that the embodiments herein can be combined with other embodiments without causing structural conflicts.

[0028] In this description, unless otherwise explicitly specified and limited, the technical terms "installation," "connection," "joining," etc., should be interpreted broadly, for example, referring to movable connections, fixed connections, or integration. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this application based on the specific circumstances.

[0029] In this description, terms such as "upper," "lower," "left," "right," "lateral," "longitudinal," "height," "length," and "width," which indicate orientation or positional relationships, are intended to accurately describe the embodiments and simplify the description, rather than limiting the parts or structures involved to have a specific orientation, or to be installed or operated in a specific orientation, and should not be construed as limiting the embodiments in this document.

[0030] In this description, terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating relative importance or limiting the number, specific order, or primary / secondary relationship of the described technical features. In this description, "multiple" means at least two.

[0031] Heat pipe reactors use a solid core, with fuel rods and heat pipes inserted into a grid matrix with circular mounting holes. Heat generated by the fuel rods is transferred to the power output end via solid-state heat transfer through the heat pipes. Because they rely on contact heat transfer, if there are gaps between the grid matrix and the heat pipes or fuel rods, it will cause an abnormally large increase in thermal resistance, resulting in a significant reduction in heat transfer efficiency. This will not only affect the reactor's output power but also reduce the reactor's safety margin and may even lead to localized overheating and accidents. Patent CN113643830A provides a technical solution for filling gaps with metal powder; however, the metal powder has poor fluidity and insufficient density, making it difficult to meet the requirements for thermal conductivity. Patent CN115862903A discloses a solution for filling with porous materials, which also suffers from insufficient thermal conductivity. Patent CN112117016B discloses a solution using liquid thermally conductive materials such as thermally conductive adhesives, but these materials have poor thermal conductivity and are prone to high-temperature decomposition. Patent CN120164642A discloses a technical solution for filling with shape memory alloys, but shape memory alloys have limited thermal cycle life and significant thermal expansion behavior, which cannot meet the service requirements of heat pipe reactors that require frequent start-up and shutdown.

[0032] To overcome the shortcomings of the prior art, one embodiment of the present invention provides an assembly method for a heat pipe reactor, which can effectively eliminate the assembly gap between the grid substrate and the heat pipes and fuel rods during the assembly process, optimize heat transfer efficiency, and improve the safety of the heat pipe reactor.

[0033] The heat pipe reactor involved in this embodiment of the invention includes a grid substrate and tubing. The grid substrate is provided with mounting holes for installing the tubing, and the tubing includes heat pipes and fuel rods. Specifically, the method is as follows: Figs. 1 to 4 As shown, it includes the following steps:

[0034] Step a): A plug 5 is installed at one end of the mounting hole 3 in the grid base 1 for sealing. The plug 5 can be made of wood, engineering plastic, ceramic, or metal. The plug 5 can be snapped into the mounting hole 3 or fixed by welding. After installing the plugs 5 at the same end of all mounting holes 3, the grid base is arranged vertically with the end of the plug 5 at the bottom and the opening of the mounting hole 3 at the top.

[0035] Step b): Inject filling slurry 4 into the mounting hole 3. In a preferred embodiment, the gap between the mounting hole 3 and the pipe 2 is 50μm-500μm, and the amount of filling slurry 4 injected into a single mounting hole can be about 5g.

[0036] In a preferred embodiment, the viscosity of the filler slurry 4 is 800 Pa·s-1200 Pa·s, and the yield strength is 180 Pa-230 Pa. The filler slurry comprises thermally conductive powder and a dispersant, wherein the thermally conductive powder comprises one or a combination of copper powder, iron powder, chromium powder, molybdenum powder, and nickel powder; and the dispersant comprises one or a combination of ethanol, phosphate, and silicate.

[0037] Step c): Insert the fitting 2 into the mounting hole 3. In a preferred embodiment, the insertion end of the fitting 2 is provided with a hemispherical or conical end to guide the filling slurry 4. The filling slurry 4 is forced to fill the gap between the fitting 2 and the mounting hole 3 by squeezing, and the air is expelled. The fitting 2 is fully inserted into the mounting hole 3, so that the filling slurry 4 fully fills the gap and partially overflows from the top of the mounting hole 3.

[0038] Step d): Remove the overflowing filler slurry 4, heat and keep the grid substrate 1 as a whole, so that the filler slurry 4 is completely transformed into the solidified filler slurry 6.

[0039] In a preferred embodiment, considering the operating conditions of the heat pipe reactor, the heating temperature does not exceed 850°C. Different methods can be used for heating in different embodiments: in some embodiments, the heat pipes inserted into the grid substrate 1 can be heated; in other embodiments, the grid substrate 1 can be heated as a whole from the outside using an electric heating device; in some embodiments, the heat pipe reactor can be started after all the pipes 2 are fully installed and inserted, using the heat generated by the fuel rods to heat the grid substrate 1.

[0040] In a comparative example, without the use of filler slurry, the existing process can control the assembly gap between the grid substrate and the tubes to approximately 100 μm. Heat transfer experiments were conducted by heating the heat pipes with electric heating rods. The results showed that when the grid substrate temperature was 800 °C, the heat pipe temperature was 1226.7 °C, a temperature difference of 426.7 °C. This data is used as a reference benchmark for evaluating the heat transfer capability of heat pipe reactors.

[0041] In the first preferred embodiment, cork plugs are used as end plugs to seal the bottom of the mounting holes. Iron powder with an average particle size of 20 μm and nickel powder with an average particle size of 10 μm are mixed in a 1:1 weight ratio as a thermally conductive powder, with ethanol as a dispersant, to obtain a filling slurry with a solid content of approximately 85%. Approximately 5 g of filling slurry is poured into each mounting hole, and then the heat pipe is inserted into the mounting hole, causing the filling slurry to flow in a forced manner to completely fill the assembly gap, with some overflowing from the top of the mounting hole. After cleaning off the overflowing filling slurry, the grid substrate is heated using an external heating device and kept at 200°C for 3 hours to allow the filling slurry to fully solidify. The cork plugs are removed, and non-destructive testing is performed using industrial CT to confirm that the filling slurry is fully filled and that there are no internal pores or gaps. The heat pipe is heated using an electric heating rod, and the temperature of the heat pipe is measured to be 925.8°C when the grid substrate temperature is 800°C, a temperature difference of 125.8°C.

[0042] In the second preferred embodiment, cork plugs are used as end plugs to seal the bottom of the mounting holes; copper powder with an average particle size of 15 μm is used as the thermally conductive powder, and ethanol, ethylene glycol, and an organic thickener are used as dispersants to mix and obtain a filling slurry with a solid content of approximately 80%; approximately 5g of filling slurry is poured into each mounting hole, and then the heat pipe is inserted into the mounting hole, causing the filling slurry to flow in a forced manner to completely fill the assembly gap, and partially overflow from the top of the mounting hole; after cleaning off the overflowing filling slurry, the grid substrate is heated using an external heating device and kept at 150°C for 5 hours to allow the filling slurry to fully solidify; the cork plugs are removed, and non-destructive testing is performed using industrial CT to confirm that the filling slurry is fully filled and that there are no air bubbles or gaps inside. The heat pipe is heated using an electric heating rod, and the temperature of the heat pipe is measured to be 833.6°C when the grid substrate temperature is 800°C, with a temperature difference of 33.6°C.

[0043] In a comparative example, a heat pipe was first inserted into the mounting hole of a vertically placed grid substrate. Then, copper powder with an average particle size of 15 μm was used as the thermally conductive powder, and ethanol, ethylene glycol, and an organic thickener were used as dispersants to obtain a filler slurry with a solid content of approximately 80%. The filler slurry was injected into the assembly gap from the end of the mounting hole, allowing it to fill the gap under injection pressure and gravity until it overflowed from the bottom of the mounting hole. The overflowing filler slurry was cleaned off, and the entire grid substrate was heated to 150°C and held at that temperature for 5 hours to allow the filler slurry to fully solidify. Non-destructive testing using industrial CT revealed significant air bubbles and pores in the lower filler slurry, indicating that injection pressure and gravity alone could not ensure sufficient flow of the filler slurry. The heat pipe was heated using an electric heating rod. The measured temperature was 875.3°C when the top grid substrate temperature was 800°C, and 966.7°C when the bottom grid substrate temperature was 800°C. It is evident that the heat transfer effect between the heat pipe and the grid substrate in the comparative example is significantly different from that in the second preferred embodiment. Furthermore, due to the inability of the filling slurry to fully fill the assembly gap, the heat transfer effect in the bottom region is severely deteriorated, resulting in significant uneven heat conduction along the axial direction of the heat pipe, which affects the reactor's efficiency and safety margin.

[0044] Another embodiment of the present invention provides a heat pipe reactor manufactured using the assembly method of the heat pipe reactor provided in any of the foregoing embodiments. By employing a forced flow method to promote the full filling of the assembly gaps by the filling slurry, the solid-state heat transfer efficiency of the reactor can be effectively improved, and the safety margin of the reactor can be further increased.

[0045] Some existing heat pipe reactor designs employ a method of directly attaching solid materials such as coatings or thin films to the tubes before assembly. This can easily lead to damage to the heat transfer layer due to friction between the grid substrate and the tubes during assembly. The scratches and debris generated during peeling can further affect the heat transfer efficiency at the contact interface during service. However, the reactor provided in this invention uses an assembly method that first fills the heat pipe with a fluid slurry and then heats and cures it. After the slurry cures, there is almost no relative displacement between the heat pipe and the substrate, effectively avoiding mechanical damage caused by friction. Furthermore, since heat transfer is achieved using the cured slurry, a slightly larger assembly gap can be maintained between the key and the mounting holes of the grid substrate, thus reducing assembly difficulty.

[0046] By utilizing forced flow to promote the uniform distribution of the filling slurry within the assembly gaps, it is possible to ensure that the assembly gaps between the tubes (heat pipes and fuel rods) and the grid substrate are fully filled, effectively avoiding the occurrence of air bubbles and pores, ensuring the uniformity of axial heat transfer performance, improving the uniformity of core temperature, preventing local overheating caused by poor local thermal conductivity, reducing thermal stress caused under long-term service conditions, effectively improving the safety margin of heat pipe reactors, and improving the reliability of heat pipe reactors in long-term service.

[0047] The purpose of the above embodiments is to provide a further detailed description of the present invention in conjunction with the accompanying drawings, so that those skilled in the art can understand the technical concept of the present invention. Within the scope of the present invention, optimization or equivalent substitution of the method steps involved, as well as combination of implementation methods in different embodiments without causing structural and principle conflicts, all fall within the protection scope of the present invention.

Claims

1. A method for assembling a heat pipe reactor, the heat pipe reactor comprising a grid substrate and tubing, the grid substrate including mounting holes for mounting the tubing, the tubing comprising heat pipes and fuel rods, characterized in that, Includes the following steps: Step a): A plug is provided at one end of the mounting hole of the grid substrate to seal it, and the grid substrate is arranged vertically so that the end with the plug is located at the bottom; Step b): Inject a filling slurry into the mounting hole, the filling slurry comprising thermally conductive powder and a dispersant; Step c): Insert the pipe fitting along the mounting hole, so that the filling slurry fills the gap between the mounting hole and the pipe fitting and overflows from the top of the mounting hole; Step d): Remove the overflowing filler slurry, heat and keep the grid substrate at a certain temperature to solidify the filler slurry.

2. The assembly method of the heat pipe reactor according to claim 1, characterized in that, The gap between the mounting hole and the pipe fitting is 50μm-500μm.

3. The assembly method of the heat pipe reactor according to claim 1 or 2, characterized in that, In step b), the viscosity of the filling slurry is 800 Pa·s-1200 Pa·s, and the yield strength is 180 Pa-230 Pa.

4. The assembly method of the heat pipe reactor according to claim 3, characterized in that, In step b), the thermally conductive powder includes one or a combination of copper powder, iron powder, chromium powder, molybdenum powder, and nickel powder; the dispersant includes one or a combination of ethanol, ethylene glycol, phosphate, and silicate; and the solid content of the filler slurry is 70%-90%.

5. The assembly method of the heat pipe reactor according to claim 1 or 2, characterized in that, In step d), the heating temperature shall not exceed 850°C.

6. The assembly method of the heat pipe reactor according to claim 5, characterized in that, In step d), the heating method is to use an external heat source to heat the heat pipe.

7. The assembly method of the heat pipe reactor according to claim 5, characterized in that, In step d), the heating method is to directly heat the grid substrate using an electric heating rod.

8. The assembly method of the heat pipe reactor according to claim 5, characterized in that, In step d), the heating method is to start the heat pipe reactor and use the fuel rods to heat the grid substrate.

9. The assembly method of the heat pipe reactor according to claim 1 or 2, characterized in that, Step d) further includes a step of using CT to detect the gap filling degree after the insulation is completed.

10. A heat pipe reactor, comprising a grid substrate, heat pipes, and fuel rods, characterized in that, The reactor is assembled using the assembly method for the heat pipe reactor as described in any one of claims 1 to 9.

Images