Fuel element and method for producing a fuel element

Abstract

The invention relates to the technical field of nuclear fuel, and discloses a fuel element and a preparation method of the fuel element, the fuel element comprises a cladding, a base body and fuel particles, the cladding is of an integrated structure manufactured through an additive manufacturing process, the cladding comprises an outer shell, a bottom plate and a cooling pipe, the outer shell and the cooling pipe are connected with the bottom plate, and the base body is arranged on the outer shell. The shell surrounds the periphery of the cooling pipe, a containing space is formed between the inner side of the shell and the outer side of the cooling pipe, and a coolant channel is formed in the inner side of the cooling pipe and penetrates through the bottom plate. The containing space is filled with the base body and the fuel particles, and the fuel particles are dispersed in the base body. According to the cladding structure, the containing space and the coolant channel are formed at the same time, cladding schemes of the fuel element can be customized according to various reactor cores of various reactor types, and the fuel element can meet the variable requirements of various novel reactor applications such as an ultra-high temperature gas cooled reactor and a gas cooled fast reactor at the same time.

Description

Technical Field

[0001] This application relates to the field of nuclear fuel technology, and in particular to a fuel element and a method for preparing the fuel element. Background Technology

[0002] Ultra-high temperature gas-cooled reactors (UHT reactors) and gas-cooled fast reactors, due to their high outlet temperatures and compact cores, combined with advanced thermoelectric conversion systems, enable the miniaturization of nuclear energy for special applications, such as power and heat supply in remote areas and energy supply for scientific research. They have become research hotspots in recent years.

[0003] Fuel elements are the core components of a reactor, requiring the ability to hold fissile materials, contain fission products, and maintain a coolable geometry over long periods. Different new reactors vary in power, burnup, operating time, and coolant proportions and flow rates, resulting in a variety of fuel element designs and complex technical approaches. Developing each new fuel element is an extremely complex systems engineering project, consuming significant time, manpower, and material resources, making it difficult to achieve engineering applications in the short term. Furthermore, the divergent fuel element designs cannot simultaneously meet the rapid development needs of multiple new reactor technologies. Summary of the Invention

[0004] This application aims to address at least one of the technical problems existing in the prior art or related technologies.

[0005] The first aspect of this application discloses a fuel element comprising: a shell, a matrix, and fuel particles. The shell is an integral structure manufactured using an additive manufacturing process and includes: an outer shell, a base plate, and a cooling pipe. The outer shell and the cooling pipe are respectively connected to the base plate. The outer shell surrounds the outer periphery of the cooling pipe, and a receiving space is formed between the inner side of the outer shell and the outer side of the cooling pipe. A coolant channel is formed on the inner side of the cooling pipe, and the coolant channel extends through the base plate. The matrix and fuel particles fill the receiving space, and the fuel particles are dispersed within the matrix.

[0006] In some of the technical solutions provided in this application, the end face contour of the shell is a regular hexagon.

[0007] In some of the technical solutions provided in this application, the fuel particles include: a core and a coating layer. The core is made of at least one of uranium dioxide, uranium nitride, or uranium carbide. The coating layer is wrapped around the outer periphery of the core and is made of pyrolytic carbon or silicon carbide.

[0008] In some of the technical solutions provided in this application, the core diameter is 200 micrometers to 2000 micrometers, and the coating thickness is 20 micrometers to 200 micrometers. The core diameter and the coating thickness are related to the operating temperature and fuel consumption.

[0009] In some technical solutions provided in this application, the fuel particles include: a first particle and a second particle, the first particle being located at both ends of the casing, the second particle being located between the two ends of the first particle, and the enrichment degree of the first particle being higher than that of the second particle.

[0010] In some of the technical solutions provided in this application, the matrix is ​​a densified matrix formed by chemical vapor infiltration.

[0011] In some of the technical solutions provided in this application, the extension path of the cooling pipe is a straight line or a curve.

[0012] In some of the technical solutions provided in this application, the substrate and the cladding are made of the same material; and / or the substrate material is at least one of silicon carbide, stainless steel, nickel-based alloy, refractory metal, beryllium oxide, yttrium hydride, and zirconium hydride.

[0013] In some of the technical solutions provided in this application, the fuel element also includes: a cover plate, which is located on the side of the housing away from the bottom plate and is connected to the end face of the housing. The cover plate seals the accommodating space, and the coolant passage runs through the cover plate.

[0014] The second aspect of this application proposes a method for preparing a fuel element. This method includes: manufacturing a cladding using an additive manufacturing process; the cladding comprising an outer shell, a base plate, and a cooling pipe; the outer shell and the cooling pipe being connected to the base plate; the outer shell surrounding the outer periphery of the cooling pipe; a coolant channel forming inside the cooling pipe; and a receiving space formed between the inner side of the outer shell and the outer side of the cooling pipe, with the coolant channel extending axially; filling the receiving space with fuel particles and a matrix; the fuel particles being dispersed within the matrix; and densifying the matrix through chemical vapor infiltration.

[0015] Compared with related technologies, the present invention has at least the following beneficial effects:

[0016] The fuel element of this application features a simple and flexible structure. The cladding structure simultaneously forms both a containment space and a coolant channel. By adjusting the shape and size of the cladding, the dimensions of both the containment space and the coolant channel can be customized to meet the specific needs of different nuclear reactors. This allows the coolant channel cross-section to be customized according to different coolant properties and heat transfer requirements, enabling the fuel element to meet the cooling requirements of different coolant types, proportions, and flow rates. The fuel particles are dispersed and micro-encapsulated within the containment space, allowing the cladding to adapt to fuel particles of various geometries and meet the different requirements of various new reactor types for fuel element size, burnup, and uranium density. The fuel element can be customized with cladding schemes for various reactor cores of different reactor types, simultaneously meeting the diverse needs of various new reactor applications such as ultra-high temperature gas-cooled reactors (UHT reactors) and gas-cooled fast reactors. This allows the fuel element to be used in UHT reactors, modular high-temperature gas-cooled reactors (MTGRs), gas-cooled fast reactors, pressurized water reactors, etc., reducing the difficulty, cost, and time of fuel element development and improving the efficiency of its engineering applications. Furthermore, when fuel elements are customized to meet different needs, their structural form only affects the preparation of the casing, avoiding adjustments to the overall process of the fuel element and improving the convenience and versatility of fuel element preparation for different needs. Attached Figure Description

[0017] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of some embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0018] Figure 1 A top view of a fuel element according to one embodiment of this application;

[0019] Figure 2 A cross-sectional view of a fuel element according to one embodiment of this application;

[0020] Figure 3 One of the schematic diagrams of the preparation process of a fuel element according to an embodiment of this application;

[0021] Figure 4 A second schematic diagram of the preparation process of a fuel element according to an embodiment of this application;

[0022] Figure 5 This is a schematic flowchart illustrating a method for preparing a fuel element according to one embodiment of this application.

[0023] in, Figures 1 to 4 The correspondence between the reference numerals and component names in the attached drawings is as follows:

[0024] 10. Fuel element; 100. Sheath; 110. Outer shell; 120. Base plate; 130. Cooling pipe; 140. Housing space; 150. Coolant passage; 200. Substrate; 300. Fuel pellet; 310. Core; 320. Coating layer; 330. First pellet; 340. Second pellet; 400. Cover plate. Detailed Implementation

[0025] To better understand the above technical solutions, the technical solutions of the embodiments of this application will be described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the embodiments of this application and the specific features in the embodiments are detailed descriptions of the technical solutions of the embodiments of this application, rather than limitations on the technical solutions of this application. In the absence of conflict, the embodiments of this application and the technical features in the embodiments can be combined with each other.

[0026] The first aspect of this application provides a fuel element 10, such as Figure 1 , Figure 2 , Figure 3 and Figure 4 As shown, the fuel element 10 includes a casing 100, a substrate 200, and fuel particles 300. The casing 100 is an integral structure manufactured using additive manufacturing. The casing 100 includes an outer shell 110, a base plate 120, and a cooling pipe 130. The outer shell 110 and the cooling pipe 130 are respectively connected to the base plate 120. The outer shell 110 surrounds the outer periphery of the cooling pipe 130. A receiving space 140 is formed between the inner side of the outer shell 110 and the outer side of the cooling pipe 130. A coolant channel 150 is formed on the inner side of the cooling pipe 130, and the coolant channel 150 penetrates the base plate 120. The substrate 200 and the fuel particles 300 fill the receiving space 140, and the fuel particles 300 are dispersed within the substrate 200.

[0027] In this embodiment, the fuel element 10 is used in a nuclear reactor device. The outer shell 110 and cooling pipes 130 are connected by a base plate 120 to form a cladding 100, which constitutes the skeleton of the fuel element 10. This cladding is integrally formed using an additive manufacturing process, exemplarily a 3D printing process. The cladding 100, relying on additive manufacturing, offers flexibility and versatility. Different structures of cladding 100 can be rapidly manufactured, making the manufacturing process of the fuel element 10 highly flexible and versatile. The outer shell 110 and cooling pipes 130 of the cladding 100 are located above the base plate 120 and are respectively connected to the top surface of the base plate 120. Multiple cooling pipes 130 are located inside the outer shell 110, so that the outer shell 110 circumferentially surrounds the outer periphery of the cooling pipes 130. A coolant channel 150 for coolant flow is formed on the inner side of the cooling pipe 130. The bottom plate 120 avoids the cooling pipe 130, so that the coolant channel 150 passes through the bottom plate 120, and the flow path of the coolant passes through the top and bottom surfaces of the fuel element 10.

[0028] The independent flow channel structure formed by the cooling pipe 130 allows the coolant channel 150 inside the casing 100 to remove the heat generated by the fuel element 10, improving the cooling effect and thermal performance of the fuel element 10. The inner diameter of the cooling pipe 130 is related to the coolant properties and heat transfer requirements. The longitudinal through-flow of the coolant channel 150 avoids lateral flow of the coolant, thereby minimizing flow-induced vibration and improving the safety and stability of the fuel element 10 during use.

[0029] Fuel particles 300 are loaded into the cladding 100, and matrix 200 powder is filled into the pores between the fuel particles 300. Alternatively, the fuel particles 300 and matrix 200 powder are uniformly mixed and then loaded into the cladding 100 together, so that the fuel particles 300 are tightly packed in the cladding 100 to form the fuel element 10. The matrix 200 and fuel particles 300 fill the receiving space 140, and the fuel particles 300 are dispersed within the matrix 200, which improves the thermal conductivity of the fuel element 10 and reduces the center temperature of the fuel element 10 to meet the requirements of various high-temperature gas-cooled reactors. For example, the matrix 200 powder can be silicon carbide powder.

[0030] The fuel element 10 of this application has a simple and flexible structure. The cladding 100 structure simultaneously forms a receiving space 140 and a coolant channel 150. To meet the needs of different nuclear reactors, the dimensions of the receiving space 140 and the coolant channel 150 can be customized by adjusting the shape and size of the cladding 100. This allows the coolant channel 150 to have a customized flow channel cross-section based on different coolant properties and heat transfer requirements, enabling the fuel element 10 to meet the cooling requirements of different coolant types, proportions, flow rates, etc. Fuel particles 300 are dispersed and micro-encapsulated within the receiving space 140, allowing the cladding 100 to adapt to fuel particles 300 of various geometries and meet the different requirements of various new reactors for fuel element 10 size, burnup, uranium density, etc. The fuel element 10 can be customized with various cladding 100 schemes for different reactor core types, enabling it to simultaneously meet the diverse needs of various new reactor applications such as ultra-high temperature gas-cooled reactors and gas-cooled fast reactors. This allows the fuel element 10 to be used in ultra-high temperature gas-cooled reactors, modular high temperature gas-cooled reactors, gas-cooled fast reactors, and pressurized water reactors, reducing the development difficulty, cost, and time of the fuel element 10, and improving its engineering application efficiency. Furthermore, when the fuel element 10 is customized for different needs, its structural form only affects the cladding 100 fabrication process, avoiding adjustments to the overall process of the fuel element 10, thus improving the ease of fabrication and versatility of the fuel element 10 to meet different requirements.

[0031] In some embodiments provided in this application, such as Figure 1 As shown, the end face profile of the outer shell 110 is a regular hexagon.

[0032] In this embodiment, the shape of the outer casing 110 is defined. The outer casing 110 is cut along the extension direction of the bottom surface, and the cross-sectional shape of the outer casing 110 is a regular hexagon, making the outer casing 110 a hexagonal prism shape. This allows multiple fuel elements 10 to be freely assembled and stacked to form nuclear reactor cores of different sizes, giving the fuel elements 10 good scalability and modularity, and increasing the adaptability and scope of use of the fuel elements 10.

[0033] In some embodiments provided in this application, such as Figure 1 As shown, the fuel particle 300 includes a core 310 and a coating layer 320. The core 310 is made of at least one of uranium dioxide, uranium nitride, or uranium carbide. The coating layer 320 is wrapped around the outer periphery of the core 310 and is made of pyrolytic carbon or silicon carbide.

[0034] In this embodiment, the structure of the fuel particle 300 is defined. The interior of the fuel particle 300 uses a core 310 made of uranium dioxide, uranium nitride, or uranium carbide as a ceramic material, giving the fuel particle 300 high temperature resistance and high inherent safety. A coating layer 320 surrounds the outer periphery of the core 310. The number of coating layers 320 can be two to five, and multiple coating layers 320 can use different materials. This creates a multi-layered coating structure for the fuel particle 300, improving the temperature resistance and fission product containment capacity of the coating layers 320, and enhancing the inherent safety of the fuel element 10.

[0035] For example, the innermost coating layer 320 is made of loose pyrolytic carbon, the middle coating layer 320 is made of silicon carbide, and the outermost coating layer 320 is made of dense pyrolytic carbon.

[0036] In some embodiments provided in this application, the core 310 has a diameter of 200 micrometers to 2000 micrometers and a coating thickness of 20 micrometers to 200 micrometers. The diameter of the core 310 and the thickness of the coating are related to the operating temperature and fuel consumption.

[0037] In this embodiment, the structure of the fuel particles 300 is further defined. The fuel particles 300 are dispersed within the matrix 200. Because the size of the fuel particles 300 is smaller than that of the cladding 100, they can fill the accommodating space 140 of the cladding 100 as much as possible. The fuel particles 300 can be arranged in close contact with each other, reducing waste in the accommodating space 140, increasing the capacity of the fuel particles 300, and improving the uranium loading of the fuel element 10. The size of the core 310 of the fuel particles 300 and the thickness of each cladding layer are designed according to the operating temperature and burnup of the nuclear reactor to meet the requirements of different temperature and burnup operation of the nuclear reactor, satisfying the reactor operation requirements such as long-term, high burnup. The diameter of the core 310 is negatively correlated with the operating temperature and burnup, while the thickness of the cladding layer is positively correlated with the operating temperature and burnup. Specifically, the higher the operating temperature and burnup, the smaller the diameter of the core 310 and the greater the thickness of the cladding layer, especially the innermost cladding layer.

[0038] In some embodiments provided in this application, such as Figure 2 As shown, the fuel particle 300 includes: a first particle 330 and a second particle 340. The first particle 330 is located at both ends of the casing 100, and the second particle 340 is located between the two ends of the first particle 330. The enrichment degree of the first particle 330 is higher than that of the second particle 340.

[0039] In this embodiment, the fuel particles 300 are divided into first particles 330 and second particles 340. Due to the different isotopes of the first particles 330 and the second particles 340, the enrichment degree of the first particles 330 is higher than that of the second particles 340. The bottom plate 120 of the casing 100 is perpendicular to its axial direction. Figure 2 The arrow at position X points along the axial direction of the cladding 100. When filling fuel particles 300 along the axial direction, the operator first lays the first high-enrichment particles 330, then the second low-enrichment particles 340, and finally the first high-enrichment particles 330, so that the first particles 330 are located at both ends of the cladding 100 along the axial direction, and the second particles 340 are located in the middle of the cladding 100 along the axial direction. Laying fuel particles 300 with different enrichment levels along the axial direction results in higher enrichment at both ends and lower enrichment in the middle of the fuel particles 300, achieving an axial zoning design of the fuel element 10 enrichment, flattening the core power distribution, making the power distribution more uniform, avoiding hot spots and hot rod problems caused by uneven core power distribution, and ensuring the safe and efficient operation of the reactor.

[0040] In some embodiments provided in this application, the substrate 200 is a densified substrate 200 formed by chemical vapor infiltration.

[0041] In this embodiment, the substrate 200 is densified by chemical vapor infiltration, which improves the structural strength and radiation resistance of the substrate 200, optimizes the thermal conductivity of the substrate 200, reduces local hot spots, makes the fuel temperature distribution more uniform, improves the safety of the fuel element 10, and avoids meltdown accidents.

[0042] In some embodiments provided in this application, such as Figure 2 and Figure 4 As shown, the extension path of the cooling pipe 130 is either a straight line or a curve.

[0043] In this embodiment, the shape of the cooling pipe 130 is defined. The cooling pipe 130 forms a coolant channel 150. Depending on the fluid characteristics and heat transfer requirements of different nuclear reactor coolants, the cooling pipe 130 can be adapted to adopt a circular pipe or curved surface structure with high heat transfer area and low flow resistance, so that the cooling pipe 130 extends along a straight line or curve to improve the thermal fluid performance of the fuel element 10.

[0044] In some embodiments provided in this application, the substrate 200 and the shell 100 are made of the same material; and / or the material of the substrate 200 is at least one of silicon carbide, stainless steel, nickel-based alloy, refractory metal, beryllium oxide, yttrium hydride, and zirconium hydride.

[0045] In this embodiment, the material of the substrate 200 is specified. The substrate 200 and the shell 100 are made of the same material, so that the substrate 200 and the shell 100 are chemically compatible, so as to coordinate the deformation caused by thermal expansion and irradiation swelling, and avoid the fuel element 10 cracking due to deformation incompatibility under high temperature irradiation environment, thereby improving the safety and stability of the fuel element 10 during use.

[0046] Silicon carbide, with its low density, low neutron absorption cross section, and good radiation performance, serves as the material for both the cladding 100 and the substrate 200, reducing the weight of the fuel element 10 and improving its radiation resistance and neutron economy. Stainless steel, nickel-based alloys, refractory metals, and beryllium oxide possess high-temperature resistance; as mature high-temperature resistant materials, they can meet the corrosive environment requirements of different reactors. Yttrium hydride and zirconium hydride have moderation capabilities; by integrating the moderation material with the coolant channel 150, the moderation function is integrated, meeting the core neutron physics requirements of different reactors.

[0047] In some embodiments provided in this application, such as Figure 2 As shown, the fuel element 10 also includes a cover plate 400, which is located on the side of the housing 110 away from the bottom plate 120 and is connected to the end face of the housing 110. The cover plate 400 seals the receiving space 140, and the coolant passage 150 passes through the cover plate 400.

[0048] In this embodiment, a cover plate 400 is fabricated on the top of the casing 100 using chemical vapor deposition. The material of the cover plate 400 is the same as that of the casing 100. The cover plate 400 and the bottom plate 120 are respectively connected to the two outer ends, so that the cover plate 400 is located at the open end of the casing 100, sealing the fuel particles 300 and the substrate 200 within the casing 100 and improving the airtightness of the containment space 140. The cover plate 400 avoids the cooling pipe 130, allowing the coolant channel 150 to pass through the cover plate 400, and the coolant flow path to pass through the top and bottom surfaces of the fuel element 10.

[0049] In one specific embodiment, this patent discloses a multi-purpose dispersed micro-encapsulated fuel element 10, which comprises an additively manufactured silicon carbide cladding 100, fuel particles 300, a substrate 200, and a cover plate 400. Based on additive manufacturing and dispersed micro-encapsulated fuel, the fuel element 10 allows for customized designs for various reactor cores of different reactor types, adapting to different coolant types, proportions, flow rates, and corrosive environments. It features high temperature resistance, flexible structure, and high inherent safety, and has broad application prospects in new high-temperature reactors.

[0050] The additively manufactured silicon carbide cladding 100 consists of a regular hexagonal outer shell 110, a cooling pipe 130, and a base plate 120, and is integrally formed using additive manufacturing. For simple structures such as direct current channels, the cladding 100 can also be prepared using traditional sintering processes. The fuel pellets 300 adopt a multi-layered cladding structure, and the core 310 uses ceramic fuels such as uranium nitride, uranium carbide, or uranium dioxide to improve temperature resistance and fission product containment capacity. The quantity and size of the fuel core 310 and the cladding layer 320 are adjusted according to requirements such as uranium loading and lifespan.

[0051] A second aspect of this application provides a method for preparing a fuel element, such as... Figure 5 As shown, the method for preparing this fuel element includes:

[0052] Step 101: Manufacture the shell using additive manufacturing process;

[0053] The cladding includes an outer shell, a base plate, and cooling pipes. The outer shell and cooling pipes are connected to the base plate. The outer shell surrounds the outer periphery of the cooling pipes. A coolant channel is formed on the inner side of the cooling pipes. An accommodating space is formed between the inner side of the outer shell and the outer side of the cooling pipes. The coolant channel is axially continuous.

[0054] Step 102: The containment space is filled by fuel particles and matrix, with the fuel particles dispersed in the matrix;

[0055] Step 103: Densify the matrix by chemical vapor infiltration.

[0056] In this embodiment, the outer shell and cooling pipes are connected to a base plate to form a casing, constituting the skeleton of the fuel element. This casing is integrally formed using an additive manufacturing process, exemplarily a 3D printing process. The casing, relying on additive manufacturing, offers flexibility and versatility, enabling the rapid production of casings with different structures, thus providing high flexibility and versatility in the fuel element manufacturing process. The outer shell and cooling pipes are located above the base plate and connected to its top surface. Multiple cooling pipes are located inside the outer shell, with the outer shell circumferentially surrounding the outer periphery of the cooling pipes. Coolant channels for coolant flow are formed inside the cooling pipes. The base plate avoids the cooling pipes, allowing the coolant channels to penetrate the base plate, and the coolant flow path to connect the top and bottom surfaces of the fuel element.

[0057] The independent flow channel structure formed by the cooling pipes allows the coolant channels inside the casing to remove the heat generated by the fuel element, improving the cooling effect and thermal performance of the fuel element. The inner diameter of the cooling pipes is related to the coolant properties and heat transfer requirements. The longitudinal flow of the coolant channels avoids lateral flow of the coolant, thereby minimizing flow-induced vibration and improving the safety and stability of the fuel element during use.

[0058] Fuel particles are loaded into the cladding shell, and matrix powder is filled into the pores between the fuel particles, or the fuel particles and matrix powder are uniformly mixed and then loaded into the cladding shell together. The matrix powder is densified through a chemical vapor infiltration process to form a dense matrix, which improves the thermal conductivity and structural strength of the matrix. This allows the fuel particles to be tightly packed into the cladding shell to form fuel elements. By filling the containment space with the matrix and fuel particles, the fuel particles are dispersed within the matrix, improving the thermal conductivity of the fuel element and reducing the center temperature of the fuel element, thus meeting the fuel element requirements of various high-temperature gas-cooled reactors. For example, the matrix powder can be silicon carbide powder.

[0059] The fuel element of this application features a simple and flexible structure. The cladding structure simultaneously forms both a containment space and a coolant channel. By adjusting the shape and size of the cladding, the dimensions of both the containment space and the coolant channel can be customized to meet the specific needs of different nuclear reactors. This allows the coolant channel cross-section to be customized according to different coolant properties and heat transfer requirements, enabling the fuel element to meet the cooling requirements of different coolant types, proportions, and flow rates. The fuel particles are dispersed and micro-encapsulated within the containment space, allowing the cladding to adapt to fuel particles of various geometries and meet the different requirements of various new reactor types for fuel element size, burnup, and uranium density. The fuel element can be customized with cladding schemes for various reactor cores of different reactor types, simultaneously meeting the diverse needs of various new reactor applications such as ultra-high temperature gas-cooled reactors (UHT reactors) and gas-cooled fast reactors. This allows the fuel element to be used in UHT reactors, modular high-temperature gas-cooled reactors (MTGRs), gas-cooled fast reactors, pressurized water reactors, etc., reducing the difficulty, cost, and time of fuel element development and improving the efficiency of its engineering applications. Furthermore, when fuel elements are customized to meet different needs, their structural form only affects the preparation of the casing, avoiding adjustments to the overall process of the fuel element and improving the convenience and versatility of fuel element preparation for different needs.

[0060] In this invention, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance; the term "multiple" refers to two or more unless otherwise explicitly defined. The terms "install," "connect," "link," and "fix" should be interpreted broadly. For example, "connect" can be a fixed connection, a detachable connection, or an integral connection; "link" can be a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0061] In the description of this invention, it should be understood that the terms "upper," "lower," "left," "right," "front," "rear," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or unit referred to must have a specific orientation or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0062] In the description of this specification, the terms "one embodiment," "some embodiments," "specific embodiment," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0063] The above are merely some embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A fuel element, characterized in that, include: The shell is an integral structure made by additive manufacturing process. The shell includes: an outer shell, a base plate and a cooling pipe. The outer shell and the cooling pipe are respectively connected to the base plate. The outer shell surrounds the outer periphery of the cooling pipe. An accommodating space is formed between the inner side of the outer shell and the outer side of the cooling pipe. A coolant channel is formed on the inner side of the cooling pipe. The coolant channel passes through the base plate. The matrix and fuel particles fill the containment space, with the fuel particles dispersed within the matrix.

2. The fuel element according to claim 1, characterized in that, The end face of the outer shell has a regular hexagonal profile.

3. The fuel element according to claim 1, characterized in that, The fuel particles include: The core material is at least one of uranium dioxide, uranium nitride, or uranium carbide; A coating layer is wrapped around the outer periphery of the core, and the material of the coating layer is pyrolytic carbon or silicon carbide.

4. The fuel element according to claim 3, characterized in that, The core has a diameter of 200 to 2000 micrometers, and the coating layer has a thickness of 20 to 200 micrometers. The diameter of the core and the thickness of the coating layer are related to the operating temperature and fuel consumption.

5. The fuel element according to claim 1, characterized in that, The fuel particles include: A first particle and a second particle, wherein the first particle is located at both ends of the shell and the second particle is located between the two ends of the first particle, and the enrichment degree of the first particle is higher than that of the second particle.

6. The fuel element according to claim 1, characterized in that, The matrix is ​​a densified matrix formed by chemical vapor infiltration.

7. The fuel element according to claim 1, characterized in that, The extension path of the cooling pipe is either a straight line or a curve.

8. The fuel element according to claim 1, characterized in that, The substrate is made of the same material as the shell; and / or The matrix material is at least one of silicon carbide, stainless steel, nickel-based alloy, refractory metal, beryllium oxide, yttrium hydride, and zirconium hydride.

9. The fuel element according to claim 1, characterized in that, Also includes: A cover plate is located on the side of the housing opposite to the bottom plate and is connected to the end face of the housing. The cover plate seals the receiving space, and the coolant channel passes through the cover plate.

10. A method for preparing a fuel element, characterized in that, include: The cladding is manufactured by additive manufacturing process. The cladding includes an outer shell, a base plate, and a cooling pipe. The outer shell and the cooling pipe are respectively connected to the base plate. The outer shell surrounds the outer periphery of the cooling pipe. A coolant channel is formed on the inner side of the cooling pipe. An accommodating space is formed between the inner side of the outer shell and the outer side of the cooling pipe. The coolant channel is axially continuous. The containment space is filled by fuel particles and a matrix, wherein the fuel particles are dispersed within the matrix. The matrix is ​​densified by chemical vapor infiltration.

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