Pre-filled nuclear fuel pellets of plate-like silicon carbide based nuclear fuel modules and applications thereof

Abstract

The application belongs to the technical field of nuclear energy, and discloses a plate-shaped silicon carbide-based nuclear fuel module pre-filled with nuclear fuel pellets and application thereof. The module comprises two silicon carbide-based plates, a non-through cylindrical hollow structure and nuclear fuel pellets. The silicon carbide-based plate is provided with a series of parallel non-through semicircular grooves on one side. The two silicon carbide-based plates are oppositely spliced by means of seamless welding on the side provided with the non-through semicircular grooves, so as to form the non-through cylindrical hollow structure. The nuclear fuel pellets are closely arranged in the non-through cylindrical hollow structure before the two silicon carbide-based plates are hot isostatic pressed and welded. The application does not need end plug sealing, has better overall structural stability, good sealing property of the plate-shaped silicon carbide-based nuclear fuel module to the nuclear fuel, high filling amount of the fuel, better energy utilization efficiency and improved safety of the nuclear reactor.

Description

Technical Field

[0001] This invention belongs to the field of nuclear energy technology, and in particular relates to a plate-shaped silicon carbide-based nuclear fuel module with pre-filled nuclear fuel pellets and its application. Background Technology

[0002] Fuel elements in a nuclear reactor are the smallest components consisting of nuclear fuel pellets and a cladding shell. Nuclear fuel is highly radioactive, and the primary function of the cladding tubes covering the fuel pellets is to protect the fuel from coolant corrosion while preventing the leakage of radioactive nuclear fission products. The selection of materials, manufacturing processes, and reliability of the cladding are crucial to the advancement, economy, and safety of nuclear power. In nuclear power plants, the fuel cladding serves to prevent the leakage of fission products, isolate the fuel pellets from the cooling water (to prevent them from reacting), and dissipate the heat generated by fission, making it the first line of defense for nuclear power plants. Currently, zirconium alloys are the most commonly used material for nuclear fuel cladding. Due to their excellent mechanical properties, corrosion resistance, and neutron economy, zirconium alloys are widely used as cladding materials for water-cooled reactors. However, under loss-of-coolant (processing water, used as coolant) accident conditions, zirconium alloys readily react violently with high-temperature steam to generate large amounts of hydrogen gas, potentially leading to an explosive nuclear accident. The 2011 Fukushima nuclear accident in Japan exposed the serious problem of poor safety and reliability of the currently used zirconium alloy cladding under accident conditions of rapid coolant loss. The U.S. Department of Energy first proposed the design concept of "Accident-Tolerant Fuel" (ATF). The core technology of ATF is the use of new cladding materials to reduce water-side corrosion, improve its oxidation resistance under high-temperature steam, and enhance its safe service performance. Analyzing the structure of nuclear fuel assemblies, traditional nuclear fuel elements are rod-shaped fuel, protected by cladding. However, due to the large length and thin wall of the cladding tube, it is easily damaged, causing nuclear leakage. The fuel loading capacity is greatly affected by the size of the cladding tube. Furthermore, heat exchange of nuclear fuel is achieved through contact between the cladding and the primary coolant, and the heat exchange efficiency is limited by the cladding surface area. Therefore, it is necessary to design a fuel cladding module with higher fuel loading capacity and higher heat exchange efficiency to replace the existing structure.

[0003] Silicon carbide composite materials have shown great potential in the field of nuclear fuel cladding due to their low thermal neutron absorption cross section, good high-temperature mechanical properties, and excellent radiation and oxidation resistance. Silicon carbide composite materials maintain good strength and radiation resistance at high temperatures, attracting significant attention in nuclear fuel research and potentially becoming the preferred cladding material for Generation 4 nuclear reactors, thereby improving reactor safety. Summary of the Invention

[0004] To overcome the problems existing in related technologies, the present invention discloses a plate-shaped silicon carbide-based nuclear fuel module with pre-filled nuclear fuel pellets and its application. In particular, it relates to the selection of materials for novel nuclear fuel cladding, the filling of nuclear fuel pellets, the structural design of nuclear fuel modules, and their preparation methods.

[0005] The technical solution is as follows: a plate-shaped silicon carbide-based nuclear fuel module pre-filled with nuclear fuel pellets, comprising two silicon carbide-based plates, a non-through-type cylindrical hollow structure, and nuclear fuel pellets;

[0006] The silicon carbide-based flat plate has several parallel non-through semi-circular grooves on one side. The non-through semi-circular grooves are spliced ​​together on opposite sides by seamless welding to form a non-through cylindrical hollow structure.

[0007] The nuclear fuel pellets are closely arranged in a non-through cylindrical hollow structure before being welded together with two silicon carbide-based flat plates by hot isostatic pressing.

[0008] Furthermore, the silicon carbide-based material of the silicon carbide-based flat plate is one or more composites of pure silicon carbide, silicon carbide composite silicon carbide fiber, and silicon carbide-based composite materials.

[0009] Furthermore, the silicon carbide-based plate has a cuboid or cube structure.

[0010] Furthermore, the non-through semi-circular groove has no slots at both ends, and the width of the groove end of the non-through semi-circular groove from the edge of the silicon carbide-based plate is 5mm-30mm.

[0011] Furthermore, the diameter of the non-through semi-circular groove is 5mm-20mm.

[0012] Furthermore, several parallel non-through semi-circular grooves are arranged in parallel in the silicon carbide-based plate, and the distance between two adjacent rows of non-through semi-circular grooves is 5mm-30mm.

[0013] Furthermore, the two rows of non-through semi-circular grooves at the two ends of the non-through semi-circular grooves are 10mm-30mm away from the edge of the silicon carbide-based plate.

[0014] Furthermore, a series of parallel guide grooves are formed on the other side of the silicon carbide-based plate.

[0015] Furthermore, the shape of the guide channel is one of rectangular, wavy, or circular.

[0016] Another object of the present invention is to provide an application of a pre-filled plate-shaped silicon carbide-based nuclear fuel module in heavy water reactors, pressurized water reactors, boiling water reactors, high-temperature gas-cooled reactors, experimental reactors, and small nuclear reactors for ships. This application utilizes the pre-filled plate-shaped silicon carbide-based nuclear fuel module in the form of a single module or through assembly.

[0017] The beneficial effects are as follows: The plate-shaped silicon carbide-based nuclear fuel module consists of two silicon carbide-based plates, a non-penetrating cylindrical hollow structure, and nuclear fuel pellets, with the nuclear fuel pellets closely arranged in the hollow structure; one side of the silicon carbide-based plate has a series of parallel non-penetrating semi-circular grooves, and the other side can selectively have a series of parallel guide channels for the passage of primary circuit water in the nuclear reactor; the two silicon carbide-based plates with the semi-circular grooves are joined together by seamless welding to form a non-penetrating cylindrical hollow structure; the nuclear fuel pellets are closely arranged in the non-penetrating cylindrical hollow structure before welding. The plate-shaped silicon carbide-based nuclear fuel module of the present invention uses silicon carbide-based materials with good high-temperature resistance and encapsulates the nuclear fuel pellets into the cladding shell by seamless welding to form an integral structure. The preparation process is simple and mature, and it can realize the low-cost preparation of plate-shaped silicon carbide-based nuclear fuel modules and the pre-filling of nuclear fuel pellets. Compared with the existing metal cladding structure, it does not require end plug sealing, has better overall structural stability, and the plate-shaped silicon carbide-based nuclear fuel module has good sealing performance for nuclear fuel, high fuel filling capacity, good energy utilization efficiency, and improves the safety of nuclear reactors.

[0018] Based on the composition of a nuclear power unit, a unit consists of 121 to 193 fuel assemblies. Each fuel assembly typically consists of 17*17 fuel rods. Currently, third-generation nuclear power units generally consist of 153 fuel units, meaning a unit requires 44,000 fuel units. If all are replaced with plate silicon carbide fuel modules, a unit would need 4,000 fuel modules. Assuming an annual fuel assembly replacement rate of one-third, a unit would require approximately 1,400 fuel modules per year. In 2023, my country had 55 operating nuclear power units, plus 8 exported units, totaling approximately 90,000 fuel modules. Assuming 8 units are put into operation annually, adding 20,000 modules each year, there would be 110,000 modules by 2024. At a price of 20,000 yuan per plate silicon carbide fuel module, the market would reach 2.2 billion yuan in 2024. Currently, my country has 26 nuclear power units under construction and 92 planned. The final number of nuclear power units built in my country will be no less than 200. The new units will require no less than 660,000 plate silicon carbide fuel modules, with a market demand of 11.2 billion yuan. The replacement cycle for plate silicon carbide fuel modules is 18 months, which translates to 190,000 modules needing to be replaced annually. This means that the market value of replacing plate silicon carbide fuel modules annually will be at least 3.6 billion yuan. If the future needs of small nuclear power units and exported units are taken into account, the market for plate silicon carbide fuel modules will be even larger.

[0019] Nuclear fuel is highly radioactive. The primary function of the cladding tubes covering nuclear fuel pellets is to protect the fuel from coolant corrosion while preventing the leakage of radioactive nuclear fission products. The selection of materials, manufacturing processes, and reliability of the cladding are crucial to the advancement, economy, and safety of nuclear power. In nuclear power plants, the fuel cladding serves as the first line of defense, preventing the leakage of fission products, isolating the fuel pellets from the cooling water (to prevent reaction between the two), and dissipating the heat generated by fission. Currently, zirconium alloys are the most commonly used material for nuclear fuel cladding both domestically and internationally. Due to its excellent mechanical properties, corrosion resistance, and neutron economy, zirconium alloys are widely used as cladding materials for water-cooled reactors. However, under loss-of-coolant (reprocessing water, serving as coolant) accident conditions, zirconium alloys readily react violently with high-temperature steam to generate large amounts of hydrogen gas, potentially leading to an explosive nuclear accident. The 2011 Fukushima nuclear accident in Japan exposed the serious problem of the poor safety and reliability of currently used zirconium alloy cladding under accident conditions of rapid coolant loss. The U.S. Department of Energy first proposed the design concept of "Accident Tolerant Fuel" (ATF). The core technology of ATF involves using novel cladding materials to reduce water-side corrosion, improve oxidation resistance under high-temperature steam, and enhance safe operation. Silicon carbide composite materials, due to their low thermal neutron absorption cross-section, good high-temperature mechanical properties, and excellent radiation and oxidation resistance, have shown great potential in the field of nuclear fuel cladding. Silicon carbide composite materials maintain good strength and radiation resistance at high temperatures, attracting significant attention in nuclear fuel research and potentially becoming the preferred cladding material for Generation 4 nuclear reactors, thereby improving reactor safety.

[0020] Traditional nuclear fuel assemblies are rod-shaped structures protected by cladding. However, due to the large length and thin walls of the cladding tubes, they are easily damaged, leading to nuclear leaks. The fuel loading capacity is significantly affected by the size of the cladding tubes. Furthermore, heat exchange of the nuclear fuel occurs through contact between the cladding and the primary coolant, and the heat exchange efficiency is limited by the surface area of ​​the cladding. Therefore, this invention designs a fuel cladding module with higher fuel loading capacity and higher heat exchange efficiency to replace the existing structure.

[0021] The plate-like structure design of the nuclear fuel cladding module in this invention improves the space utilization of nuclear fuel and avoids the risk of nuclear fuel leakage. The silicon carbide-based nuclear fuel module can achieve seamless welding using conventional hot isostatic pressing, avoiding the end-plug welding process of traditional cladding tubes and improving the airtightness of the nuclear fuel cladding. The plate-like silicon carbide-based nuclear fuel module with pre-filled nuclear fuel pellets uses silicon carbide-based materials as the cladding material, improving the inherent safety of the nuclear reactor. This invention creatively proposes a novel fuel module structure, breaking away from the original cladding structure model. Attached Figure Description

[0022] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this disclosure and, together with the description, serve to explain the principles of this disclosure;

[0023] Figure 1 This is a structural diagram of a plate-shaped silicon carbide-based nuclear fuel module (prefilled nuclear fuel pellet) without flow channels provided in an embodiment of the present invention.

[0024] Figure 2 This is a two-dimensional structural diagram of a plate-shaped silicon carbide-based nuclear fuel module (pre-filled nuclear fuel pellet) with wavy flow channels on the side provided in an embodiment of the present invention.

[0025] Figure 3 This is a two-dimensional structural diagram of a plate-shaped silicon carbide-based nuclear fuel module (pre-filled nuclear fuel pellet) with rectangular flow channels on the side provided in an embodiment of the present invention.

[0026] In the diagram: 1. Silicon carbide-based flat plate; 2. Non-through semi-circular groove; 3. Nuclear fuel pellet; 4. Flow channel. Detailed Implementation

[0027] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0028] The innovation of this invention lies in:

[0029] 1. Inherent Safety. Currently, zirconium alloys are commercially available as cladding materials for nuclear reactors. However, zirconium alloys have poor high-temperature oxidation resistance, low strength, and are susceptible to a zirconium-water reaction under high-temperature steam conditions, potentially causing a hydrogen explosion. Therefore, zirconium alloys have low inherent safety. Silicon carbide materials, on the other hand, have a high melting point (>2700℃), high strength, and corrosion resistance. They also exhibit excellent resistance to neutron radiation and a low neutron absorption cross-section. Silicon carbide materials demonstrate high inherent safety under accident conditions and show great application potential in the field of nuclear reactor fuel elements.

[0030] 2. The plate-shaped cladding structure design, compared with the traditional tubular cladding structure design, can improve space utilization, thereby improving the heat exchange efficiency of the nuclear reactor system and the power generation efficiency.

[0031] 3. Traditional cladding tubes require end plug welding, which is a complex process. The plate-shaped silicon carbide structure design can be welded using conventional hot isostatic pressing methods, achieving seamless welding. This avoids the airtightness problems of traditional cladding tube welding and improves the safety of nuclear reactors.

[0032] Example 1, such as Figure 1 As shown, this embodiment of the invention provides a plate-shaped silicon carbide-based nuclear fuel module with pre-filled nuclear fuel pellets, comprising two silicon carbide-based flat plates 1, a non-through cylindrical hollow structure, and nuclear fuel pellets 3.

[0033] The silicon carbide-based flat plate 1 has a series of parallel, non-through semi-circular grooves 2 on one side, and a series of parallel guide grooves 4 can be selectively formed on the other side (e.g., Figure 2 , Figure 3 As shown), it is used for the passage of primary circuit water in nuclear reactors; the two silicon carbide-based flat plates 1 have one side containing a non-through semi-circular groove 2 which are spliced ​​together by seamless welding to form a non-through cylindrical hollow structure.

[0034] The nuclear fuel pellets 3 are closely arranged in a non-through cylindrical hollow structure before welding.

[0035] It is understandable that the design of plate cladding structure can improve space utilization compared to the traditional tubular cladding structure design, thereby improving the heat exchange efficiency of the nuclear reactor system and the power generation efficiency. Traditional cladding tubes require end plug welding, which is a complex process. The plate silicon carbide structure design can be welded using conventional hot isostatic pressing methods, which can achieve seamless welding, avoid the airtightness problem of traditional cladding tube welding, and improve the safety of the nuclear reactor.

[0036] For example, the nuclear fuel pellets 3 are pre-filled in a non-through cylindrical hollow structure before welding. The energy of the nuclear fuel pellets 3 is directly transferred to the silicon carbide-based plate 1, and the outside of the silicon carbide-based plate 1 is in direct contact with the primary circuit water of the nuclear reactor, thereby achieving efficient energy transfer.

[0037] The silicon carbide-based material of the silicon carbide-based plate 1 is pure silicon carbide, silicon carbide composite silicon carbide fiber, or one or more composites of other silicon carbide-based composite materials.

[0038] For example, the silicon carbide-based plate 1 has a cuboid or cube structure.

[0039] It is understood that the silicon carbide-based flat plate 1 can achieve modular splicing and increase the loading capacity of nuclear fuel pellets 3.

[0040] For example, the non-through semi-circular groove 2 has no slots at both ends, and the width of the groove end of the non-through semi-circular groove 2 from the edge of the silicon carbide-based plate 1 is 5mm-30mm. If it exceeds 30mm, the number of slots will be reduced, which will further reduce the filling amount.

[0041] Preferably, the non-through semi-circular groove 2 has a diameter of 5mm-20mm and a depth equal to its radius. This allows nuclear fuel to be encapsulated within a silicon carbide cladding.

[0042] For example, a series of parallel non-through semi-circular grooves 2 are arranged in parallel in a silicon carbide-based plate 1, and the spacing between two adjacent rows of non-through semi-circular grooves 2 is 5mm-30mm.

[0043] Preferably, the two rows of non-through semi-circular grooves 2 located at the two ends of the series of parallel non-through semi-circular grooves 2 are 10mm-30mm away from the edge of the silicon carbide-based plate 1.

[0044] For example, the nuclear fuel pellet 3 is one of the following: cylindrical uranium, aluminum-uranium alloy, molybdenum-uranium alloy, uranium-zirconium hydride alloy, U3Si ceramic, uranium-plutonium oxide ceramic, uranium-plutonium carbide ceramic, uranium-plutonium nitride ceramic, uranium oxide ceramic, UAl4-Al dispersion, uranium oxide-aluminum, and uranium oxide-thorium-(pyrolytic graphite, silicon carbide)-graphite dispersion nuclear fuel;

[0045] Plate-shaped silicon carbide-based nuclear fuel modules can be produced using conventional hot isostatic pressing (HIP) methods. The raw material is nano-sized silicon carbide-based powder, and the prepared silicon carbide structure can meet the structural performance requirements of nuclear fuel modules.

[0046] like Figure 2 , Figure 3 As shown, the shape of the guide channel 4 can be rectangular, wavy, or circular.

[0047] Example 2: The pre-filled nuclear fuel pellets of the plate-shaped silicon carbide-based nuclear fuel module are used in heavy water reactors, pressurized water reactors, boiling water reactors, high-temperature gas-cooled reactors, experimental reactors, and small nuclear reactors for ships.

[0048] In applications, pre-filled plate-shaped silicon carbide-based nuclear fuel modules can be used directly as individual modules, or they can be assembled and used together to achieve large-scale production of components.

[0049] As demonstrated by the above examples, inherent safety is a crucial performance characteristic of cladding materials used in nuclear reactors. Currently, zirconium alloys are commercially available; however, zirconium alloys have poor high-temperature oxidation resistance, low strength, and are susceptible to a zirconium-water reaction under high-temperature steam conditions, potentially leading to a hydrogen explosion. Therefore, zirconium alloys have low inherent safety. Silicon carbide materials, on the other hand, possess a high melting point (>2700℃), high strength, and corrosion resistance. They also exhibit excellent resistance to neutron radiation and a low neutron absorption cross-section. Silicon carbide materials demonstrate high inherent safety under accident conditions and show promising application potential in the field of nuclear reactor fuel elements.

[0050] Compared with the traditional tubular cladding structure, the plate-shaped cladding structure design can improve space utilization, thereby improving the heat exchange efficiency of the nuclear reactor system and the power generation efficiency.

[0051] Traditional cladding tubes require end plug welding, which is a complex process. The plate-shaped silicon carbide structure design can be welded using conventional hot isostatic pressing methods, achieving seamless welding. This avoids the airtightness problems of traditional cladding tube welding and improves the safety of nuclear reactors.

[0052] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail or recorded in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0053] Experimental applications demonstrate that the plate-shaped silicon carbide-based nuclear fuel module with pre-filled nuclear fuel pellets provided by this invention, using silicon carbide-based materials as cladding material, improves the inherent safety of the nuclear reactor. The plate-shaped structure design of the nuclear fuel cladding module improves the space utilization of the nuclear fuel and avoids the risk of nuclear fuel leakage. The silicon carbide-based nuclear fuel module can achieve seamless welding using conventional hot isostatic pressing, avoiding the end-plug welding process of traditional cladding tubes and improving the airtightness of the nuclear fuel cladding. The plate-shaped silicon carbide-based nuclear fuel module with pre-filled nuclear fuel pellets exhibits higher resistance to accident conditions during reactor operation, improving the safety factor of the nuclear reaction.

[0054] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent substitutions, and improvements made by those skilled in the art within the scope of the technology disclosed in the present invention, and within the spirit and principles of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A plate-shaped silicon carbide-based nuclear fuel module pre-filled with nuclear fuel pellets, characterized in that, The module includes two silicon carbide-based flat plates (1), a non-through cylindrical hollow structure, and nuclear fuel pellets (3); The silicon carbide-based flat plate (1) has several parallel non-through semi-circular grooves (2) on one side. The non-through semi-circular grooves (2) are spliced ​​together on one side by seamless welding to form a non-through cylindrical hollow structure. The nuclear fuel pellets (3) are closely arranged in a non-through cylindrical hollow structure before the two silicon carbide-based flat plates (1) are hot isostatically welded.

2. The plate-shaped silicon carbide-based nuclear fuel module with pre-filled nuclear fuel pellets according to claim 1, characterized in that, The silicon carbide-based material of the silicon carbide-based flat plate (1) is one or more composites of pure silicon carbide, silicon carbide composite silicon carbide fiber, and silicon carbide-based composite material.

3. The plate-shaped silicon carbide-based nuclear fuel module with pre-filled nuclear fuel pellets according to claim 1, characterized in that, The silicon carbide-based flat plate (1) has a cuboid or cube structure.

4. The plate-shaped silicon carbide-based nuclear fuel module with pre-filled nuclear fuel pellets according to claim 1, characterized in that, The non-through semi-circular groove (2) has no grooves at both ends, and the width of the groove end of the non-through semi-circular groove (2) from the edge of the silicon carbide-based plate (1) is 5mm-30mm.

5. The plate-shaped silicon carbide-based nuclear fuel module with pre-filled nuclear fuel pellets according to claim 4, characterized in that, The diameter of the non-through semi-circular groove (2) is 5mm-20mm.

6. The plate-shaped silicon carbide-based nuclear fuel module with pre-filled nuclear fuel pellets according to claim 1, characterized in that, Several parallel non-through semi-circular grooves (2) are arranged in parallel in a silicon carbide-based plate (1), and the distance between two adjacent rows of non-through semi-circular grooves (2) is 5mm-30mm.

7. The plate-shaped silicon carbide-based nuclear fuel module with pre-filled nuclear fuel pellets according to claim 6, characterized in that, The two rows of non-through semi-circular grooves (2) located at the two ends of the non-through semi-circular grooves (2) are 10mm-30mm away from the edge of the silicon carbide-based plate (1).

8. The plate-shaped silicon carbide-based nuclear fuel module with pre-filled nuclear fuel pellets according to claim 1, characterized in that, A series of parallel guide grooves (4) are opened on the other side of the silicon carbide-based flat plate (1).

9. The plate-shaped silicon carbide-based nuclear fuel module with pre-filled nuclear fuel pellets according to claim 8, characterized in that, The guide groove (4) is rectangular, wavy, or circular in shape.

10. The application of a pre-filled plate-shaped silicon carbide-based nuclear fuel module in heavy water reactors, pressurized water reactors, boiling water reactors, high-temperature gas-cooled reactors, experimental reactors, and small nuclear reactors for ships, characterized in that, This application utilizes the plate-shaped silicon carbide-based nuclear fuel module of any one of claims 1-9, either as a single module or by assembly.

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