Nuclear fuel and preparation method thereof

Abstract

The invention discloses a nuclear fuel and a preparation method thereof, belongs to the technical field of nuclear reactors, and mainly aims to improve the safety and stability of heat transfer. According to the main technical scheme, the nuclear fuel comprises an upper cladding cover plate and a lower cladding cover plate which are oppositely arranged; the perforated plate is arranged between the upper cladding cover plate and the lower cladding cover plate, the perforated plate is of a honeycomb structure, and a plurality of honeycomb-shaped compartments are formed in the honeycomb structure; a fuel element is arranged in each honeycomb-shaped compartment, the upper surface of each fuel element is in contact with the upper cladding cover plate, the lower surface of each fuel element is in contact with the lower cladding cover plate, and the peripheral surface of each fuel element is in contact with the wall of the corresponding honeycomb-shaped compartment.

Description

Technical Field

[0001] The present application belongs to the field of nuclear reactor technology, and specifically relates to a nuclear fuel and a preparation method thereof. Background Art

[0002] In order to achieve higher burnup depth and ensure economical, efficient and long-life operation of nuclear reactors, it is urgent to improve nuclear fuel safety.

[0003] However, conventional nuclear reactors use a fuel structure that encloses fuel pellets within a cladding. However, due to the gaps between the fuel pellets and the cladding, and the low thermal conductivity of the fuel pellets themselves, a large temperature gradient develops between the fuel pellets and the cladding during nuclear reactor operation. Under the high-temperature, high-pressure operating environment of a nuclear reactor, this large temperature gradient can trigger interaction between the fuel pellets and the cladding. In severe cases, this can cause fuel element rupture, posing a significant threat to the safe operation of the nuclear reactor. Summary of the Invention

[0004] In view of this, the present application provides a nuclear fuel and a preparation method thereof, the main purpose of which is to improve the safety and stability of heat transfer.

[0005] To achieve the above objectives, this application mainly provides the following technical solutions:

[0006] In one aspect of the present application, a nuclear fuel is provided, comprising:

[0007] Upper and lower cladding plates arranged opposite to each other;

[0008] A porous plate disposed between the upper cladding plate and the lower cladding plate, wherein the porous plate has a honeycomb structure, and the honeycomb structure forms a plurality of honeycomb compartments;

[0009] A fuel element is arranged in each of the honeycomb cells, the upper surface of the fuel element contacts the upper cladding plate, the lower surface of the fuel element contacts the lower cladding plate, and the outer peripheral surface of the fuel element contacts the wall of the honeycomb cell.

[0010] Optionally, the upper surface, the lower surface and the peripheral surface of the fuel element are all provided with a diffusion barrier layer, and the diffusion barrier layer is a graphite coating or a metal chromium coating.

[0011] Optionally, the upper cladding plate, the lower cladding plate and the porous plate are all made of zirconium alloy, the thickness of the upper cladding plate and the lower cladding plate is 0.2-0.8 mm, and the thickness of the porous plate is 1.0-2.0 mm.

[0012] Another aspect of the present application provides a method for preparing nuclear fuel, for preparing any one of the nuclear fuels described above, the method comprising:

[0013] preparing the fuel element;

[0014] Loading the fuel elements into the honeycomb compartments of the porous plate, and welding the upper cladding plate, the lower cladding plate, and the porous plate to form intermediate nuclear fuel;

[0015] Hot-pressing, diffusion-bonding treatment of the intermediate nuclear fuel;

[0016] The intermediate nuclear fuel is heat treated in a zirconium alloy beta phase.

[0017] Optionally, preparing the fuel element includes:

[0018] Mixing ceramic phase raw material particles and metal matrix material powder to form a mixed powder system;

[0019] Filling the mixed powder system into a mold and hot pressing it into shape;

[0020] Wherein, the volume content of the ceramic phase raw material particles in the mixed powder system does not exceed 30%.

[0021] Optionally, preparing the fuel element includes:

[0022] Ceramic phase raw material particles and metal matrix material powder are loaded into the mold layer by layer and hot pressed into shape.

[0023] Optionally, when the intermediate nuclear fuel is treated by hot pressure diffusion bonding, the hot pressure parameter is 80-150 MPa, the treatment temperature is 750-830° C., and the treatment time is 1-2 hours.

[0024] Optionally, when the intermediate nuclear fuel is heat-treated with the zirconium alloy β phase, the treatment temperature is 950-1010° C. and the treatment time is 3-10 minutes.

[0025] Optionally, before loading the fuel elements into the honeycomb-shaped compartments of the porous plate, the method further comprises:

[0026] The upper cladding cover plate and the lower cladding cover plate are subjected to sandblasting.

[0027] Optionally, after the zirconium alloy β-phase heat treatment of the intermediate nuclear fuel, the method further comprises:

[0028] The intermediate nuclear fuel is sandblasted.

[0029] By means of the above technical solution, this application has at least the following beneficial effects:

[0030] The nuclear fuel and its preparation method provided in the embodiments of the present application provide a stable support for the fuel elements by providing a porous plate as a honeycomb structure, so that each fuel element is precisely placed in the honeycomb compartment and closely adheres to the upper and lower cladding plates and the walls of the honeycomb compartment. This effectively disperses the pressure and stress generated during reactor operation, enhances the overall structural strength of the nuclear fuel, and improves the nuclear fuel's ability to accommodate fission gas. As a result, the nuclear fuel can achieve high burnup, extend its service life, and contribute to the economical, efficient, and long-term stable operation of the nuclear reactor. Furthermore, the fuel elements are in direct contact with the upper and lower cladding plates and the walls of the honeycomb compartment, eliminating the interstitial thermal resistance between the fuel elements and the cladding. This allows for more efficient transfer of heat generated by the fuel elements to the cladding and, in turn, to the coolant, helping to lower the temperature inside the fuel elements, reduce temperature gradients, and mitigate the interaction between the fuel elements and the cladding due to thermal stress, thereby improving the safety and reliability of the nuclear fuel. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a schematic structural diagram of nuclear fuel according to an optional embodiment of the present application;

[0032] Figure 2 This is a flow chart of a nuclear fuel preparation method according to an optional embodiment of the present application;

[0033] Figure 3 A flowchart of a nuclear fuel preparation method according to another optional embodiment of the present application;

[0034] Figure 4 The tensile curves of the interfaces between the upper cladding plate, the lower cladding plate and the fuel element at room temperature are shown.

[0035] The reference numerals indicate:

[0036] 1. Upper cladding plate; 2. Lower cladding plate; 3. Perforated plate; 31. Honeycomb compartment. DETAILED DESCRIPTION

[0037] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0038] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. Throughout the description of this application, "plurality" means two or more, unless otherwise specifically defined.

[0039] In this application, unless otherwise specified or limited, the terms "mounted," "connected," "connect," "fixed," etc. should be understood broadly. For example, they can refer to fixed connection, detachable connection, or integral connection; mechanical connection or electrical connection; direct connection or indirect connection through an intermediate medium; or internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on specific circumstances.

[0040] The preferred embodiments of the present application are described below in conjunction with the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present application and are not used to limit the present application.

[0041] See also Figure 1 As shown, according to an embodiment of the present application, a nuclear fuel is provided, including: an upper cladding plate 1 and a lower cladding plate 2 arranged opposite to each other; a porous plate 3 arranged between the upper cladding plate 1 and the lower cladding plate 2, the porous plate 3 being a honeycomb structure, and the honeycomb structure forming a plurality of honeycomb compartments 31; a fuel element is arranged in each honeycomb compartment 31, the upper surface of the fuel element is in contact with the upper cladding plate 1, the lower surface of the fuel element is in contact with the lower cladding plate 2, and the outer peripheral surface of the fuel element is in contact with the wall of the honeycomb compartment 31.

[0042] In this embodiment, the porous plate 3 forms a honeycomb structure, providing stable support for the fuel elements. Each fuel element is precisely positioned within the honeycomb cells 31, closely conforming to the upper and lower cladding plates 1 and 2, and the walls of the honeycomb cells 31. This effectively disperses the pressure and stress generated during reactor operation, enhances the overall structural strength of the nuclear fuel, and improves its ability to contain fission gases. This enables high fuel burnup and extends its service life, contributing to the economical, efficient, and long-term stable operation of the nuclear reactor. Furthermore, the direct contact between the fuel elements and the upper and lower cladding plates 1 and 2, as well as the walls of the honeycomb cells 31, eliminates the interstitial thermal resistance between the fuel elements and the cladding. This allows for more efficient transfer of heat generated by the fuel elements to the cladding and, subsequently, to the coolant. This helps lower the temperature within the fuel elements, reduces temperature gradients, mitigates interactions between the fuel elements and the cladding caused by thermal stress, and improves the safety and reliability of the nuclear fuel.

[0043] The upper cladding plate 1 and the lower cladding plate 2 together form the cladding of the nuclear fuel. The upper cladding plate 1 and the lower cladding plate 2 are arranged opposite to each other to protect the internal structure and block the external environment.

[0044] Specifically, the upper cladding plate 1 and the lower cladding plate 2 are generally flat plates that match the shape of the porous plate 3. They can cover the porous plate 3 and the fuel elements therein, providing protection and restraint. It will be appreciated that in actual applications, the size and shape of the upper cladding plate 1 and the lower cladding plate 2 can be determined based on the specific design and application scenario of the nuclear fuel to ensure compatibility with the overall nuclear fuel structure.

[0045] The honeycomb structure of the porous plate 3 is composed of hexagonal units, with each hexagonal unit corresponding to a honeycomb cell 31. When the reactor is operating, various complex forces are generated, such as pressure fluctuations caused by nuclear reactions and the impact of coolant flow. The honeycomb structure acts like a sturdy framework, evenly distributing these forces to various parts and preventing excessive local stress. Each honeycomb cell 31 acts as an independent support unit, working together to support the fuel element and greatly enhancing the overall structural strength of the nuclear fuel.

[0046] Specifically, each honeycomb cell 31 houses a fuel element. When the fuel element is placed in the honeycomb cell 31, it is in close contact with the surrounding structure, fixing the fuel element's position within the honeycomb cell 31. This not only ensures that the fuel element will not wobble or shift within the cell, but also forms a mechanically integrated whole. When pressure and stress are generated during reactor operation, the forces exerted on the fuel element can be evenly transmitted through contact with the upper cladding plate 1, the lower cladding plate 2, and the walls of the honeycomb cell 31, further improving structural stability. It should be noted that in terms of improving structural stability, during reactor operation, different components will expand and contract to varying degrees due to factors such as temperature changes and different stress conditions. If there are large gaps between the fuel element and other components, the fuel element may be subjected to uneven forces during the expansion and contraction of these components, resulting in damage. The close fit between the fuel elements and the surrounding structure enhances the coordinated deformation capabilities of the various components, effectively reducing the risk of damage to the fuel elements due to relative displacement between components. Regarding the enhanced ability to contain fission gases: During the fission process, nuclear fuel produces fission gases such as krypton and xenon. If these gases are not effectively contained and processed, they will accumulate inside the fuel elements or between the fuel elements and the cladding, generating additional pressure and affecting the performance and safety of the nuclear fuel. Because the fuel elements fit tightly with the surrounding structure, the space within the entire nuclear fuel structure is effectively divided and utilized. The honeycomb cells 31 and the tightly fitting cladding plates can constrain the fission gases to a certain extent, preventing them from spreading disorderly around the fuel elements, thereby improving the nuclear fuel's ability to contain fission gases. This helps maintain stable pressure inside the fuel elements, reducing deformation or cracking caused by gas accumulation. This allows the nuclear fuel to maintain good performance even at high burnup, extending its service life and ensuring long-term stable operation of the nuclear reactor. Regarding eliminating interstitial thermal resistance: In traditional nuclear fuel structures, air gaps exist between the fuel pellets and the cladding, and the fuel pellets themselves have low thermal conductivity. This results in significant thermal resistance during heat transfer from the fuel pellets to the cladding. The gas in these gaps (typically inert gases) has a much lower thermal conductivity than solid materials, hindering heat transfer and creating a large temperature gradient between the fuel pellets and the cladding. The fuel elements, however, are tightly bonded to the surrounding structure, completely eliminating interstitial thermal resistance between the fuel and cladding. Heat is transferred directly from the fuel element to the cladding through solid contact, significantly improving heat transfer efficiency. This direct contact creates a more direct and efficient heat transfer path, avoiding heat accumulation within the fuel element due to interstitial thermal resistance. As the internal temperature of the fuel element decreases, the temperature gradient between the fuel element and the cladding also decreases.Smaller temperature gradients mean that the difference in thermal expansion and contraction between the fuel elements and the cladding is minimized, thereby reducing the interaction between the fuel and cladding caused by thermal stress, effectively improving the safety and reliability of the nuclear fuel and providing a strong guarantee for the safe operation of the nuclear reactor. Furthermore, each honeycomb-shaped compartment 31 is independent of each other and does not communicate with each other. Even in the extreme case of a cladding rupture, only a few compartments corresponding to the ruptured area may experience corrosion and cracking. The remaining numerous compartments can remain intact, effectively preventing large amounts of radioactive material from leaking into the coolant due to compartment connectivity. This greatly ensures the cleanliness of the coolant, reduces the risk of nuclear leakage, and improves the overall safety and reliability of the nuclear fuel.

[0047] In some possible embodiments disclosed in the present application, the upper surface, the lower surface and the peripheral surface of the fuel element are all provided with a diffusion barrier layer, and the diffusion barrier layer is a graphite coating or a metal chromium coating.

[0048] In this embodiment, the diffusion barrier layer is provided to prevent the fission products and other impurities in the fuel element from diffusing into the surrounding environment, thereby preventing the fission products from chemically reacting with the cladding material, and avoiding degradation or damage to the cladding performance due to the reaction.

[0049] The diffusion barrier layer is formed by uniformly coating graphite material or metallic chromium on the surface of the fuel element.

[0050] Specifically, when the diffusion barrier layer is a graphite coating, it effectively inhibits the outward diffusion of substances within the fuel element and prevents impurities from the external environment from penetrating the fuel element. Furthermore, it can withstand the high temperatures within the reactor, reducing the performance changes of the fuel element caused by high temperatures. It can also improve the thermal conductivity of the fuel element to a certain extent, dissipating heat more evenly. When the diffusion barrier layer is a metallic chromium coating, it forms a dense protective film on the surface of the fuel element, preventing chemical reactions between the fuel and the surrounding medium and protecting the fuel element from corrosion. It also facilitates heat conduction, ensuring that the fuel element maintains stable performance during operation and can withstand certain mechanical and thermal stresses.

[0051] In some possible embodiments disclosed in the present application, the upper cladding plate 1, the lower cladding plate 2 and the porous plate 3 are all made of zirconium alloy, the thickness of the upper cladding plate 1 and the lower cladding plate 2 is 0.2 to 0.8 mm, and the thickness of the porous plate 3 is 1.0 to 2.0 mm.

[0052] In this embodiment, the zirconium alloy exhibits excellent corrosion resistance, making it resistant to erosion by media such as the coolant in a nuclear reactor. During long-term operation, it effectively prevents corrosion damage to the cladding and porous plate 3, ensuring the integrity of the nuclear fuel and preventing leakage of radioactive materials due to corrosion, thereby improving reactor safety. Furthermore, the zirconium alloy's low neutron absorption cross-section does not significantly affect the neutron flux distribution and reactivity within the nuclear reactor, thus facilitating stable operation of the nuclear reactor and improving nuclear fuel utilization.

[0053] The upper cladding plate 1 and the lower cladding plate 2 have the same thickness. For example, the thickness of the upper cladding plate 1 and the lower cladding plate 2 is 0.2 mm, or 0.3 mm, or 0.4 mm, or 0.5 mm, or 0.6 mm, or 0.7 mm, or 0.8 mm. It is understood that the thickness of the upper cladding plate 1 and the lower cladding plate 2 can also be other values ​​besides the above values, as long as the thickness of the upper cladding plate 1 and the lower cladding plate 2 is within the range of 0.2 to 0.8 mm. It should be noted that the thickness of the upper cladding plate 1 and the lower cladding plate 2 is between 0.2 and 0.8 mm, which can provide sufficient protection to prevent the fuel elements from being affected by the external environment while ensuring good heat transfer performance.

[0054] Among them, the thickness of the porous plate 3 can be 1.0mm, or 1.1mm, or 1.2mm, or 1.3mm, or 1.4mm, or 1.5mm, or 1.6mm, or 1.7mm, or 1.8mm, or 1.9mm, or 2.0mm, etc. It is understandable that the thickness of the porous plate 3 can also be other values ​​other than the above values, as long as the thickness of the porous plate 3 is within the range of 1.0 to 2.0mm. It should be noted that the thickness of the porous plate 3 is between 1.0 and 2.0mm, which helps to ensure the structural stability of the porous plate 3, so that it can withstand the weight of the fuel elements and the various forces it is subjected to during the operation of the reactor, and is not easily deformed or damaged. At the same time, it can cooperate with the cladding plate to better guide the coolant to flow around the fuel elements, achieve a uniform cooling effect, avoid the occurrence of local overheating, and further improve the safety and reliability of nuclear fuel.

[0055] Specifically, when the thickness of the porous plate 3 is 2.0 mm, the side length of each hexagonal unit on the porous plate 3 is 25 mm, and the width of a single side is 1.5 mm.

[0056] Furthermore, in order to fully illustrate the specific implementation process of this embodiment, a nuclear fuel preparation method is provided, see Figure 2 As shown, the method includes:

[0057] Step S101: preparing fuel elements.

[0058] In some specific examples, the steps for preparing a fuel element include: mixing ceramic phase raw material particles with metal matrix material powder to form a mixed powder system; loading the mixed powder system into a mold, and hot pressing to form the system. In other specific examples, the steps for preparing a fuel element include: loading ceramic phase raw material particles and metal matrix material powder into a mold layer by layer, and hot pressing to form the system.

[0059] The volume content of ceramic phase raw material particles in the mixed powder system does not exceed 30%.

[0060] Among them, the ceramic phase raw material particles available for mixing include uranium dioxide (UO2) particles, uranium silicide (U3Si2) particles, uranium-molybdenum alloy (UMo) particles, uranium-zirconium alloy (UZr) particles, uranium nitride (UN) particles, and plutonium-uranium oxide (MOX) particles.

[0061] Among them, the metal matrix material powders available for mixing include aluminum (Al) powder, zirconium (Zr) powder, stainless steel (such as 316L stainless steel) powder, and the like.

[0062] The hot pressing forming temperature may be 740° C., and the hot pressing forming pressure may be 80 MPa.

[0063] Step S102: loading fuel elements into the honeycomb cells 31 of the porous plate 3, and welding the upper cladding plate 1, the lower cladding plate 2 and the porous plate 3 to form an intermediate nuclear fuel.

[0064] Here, loading the fuel elements into the honeycomb-shaped compartments 31 allows for precise positioning and securement of the fuel elements, maintaining a stable position during subsequent processing and reactor operation. This prevents collisions between fuel elements or friction with the cladding due to shaking or displacement, reducing the risk of damage. Welding the upper and lower cladding plates 1 and 2 to the porous plate 3 creates a sealed structure, providing excellent protection for the fuel elements.

[0065] The upper and lower cladding plates 1, 2, and the porous plate 3 are welded using a vacuum electron beam welding process. This process can be performed in a vacuum environment, effectively preventing air from entering the honeycomb cells 31. This ensures that the welding process is not affected by airborne impurities, ensuring weld quality and preventing adverse effects such as oxidation of key components within the cells due to exposure to air.

[0066] Step S103: hot pressing and diffusion bonding treatment of the intermediate nuclear fuel.

[0067] Here, through hot-pressing and diffusion bonding, the gaps between the upper cladding plate 1, lower cladding plate 2, porous plate 3, and fuel element gradually disappear, forming a strong metallurgical bond. This improves the connection strength between the components, making the intermediate nuclear fuel a single, integrated structure that can better withstand the various forces and thermal stresses generated during nuclear reactor operation.

[0068] Among them, when the intermediate nuclear fuel is subjected to hot pressing diffusion bonding treatment, the hot pressing pressure is controlled between 80 and 150 MPa, the treatment temperature is maintained in the range of 750 to 830°C, and the treatment time is set to 1 to 2 hours.

[0069] Step S104: heat-treating the intermediate nuclear fuel in the zirconium alloy β phase.

[0070] Here, the intermediate nuclear fuel is heated to the zirconium alloy's β-phase temperature range and held for a period of time to induce a partial β-phase transformation at the zirconium alloy's diffusion interface. The β-phase structure is then adjusted and optimized by controlling the cooling rate. This homogenizes the grain structure at the zirconium alloy's diffusion interface, enhancing its strength, toughness, and corrosion resistance. It also improves its dimensional stability, enabling long-term stable operation in the high-temperature, high-pressure, and intense radiation environments of a nuclear reactor, thereby ensuring the reliability and safety of the nuclear fuel.

[0071] Among them, when performing zirconium alloy β-phase heat treatment on the intermediate nuclear fuel, the heat treatment temperature needs to be maintained between 950 and 1010°C, and the treatment time is controlled within 3 to 10 minutes.

[0072] After the intermediate fuel's zirconium alloy β-phase heat treatment is completed, it is quickly placed in a helium flow for cooling. Simultaneously, a mold is used to secure the intermediate fuel to prevent deformation during the cooling process and excessive oxidation from contact with air.

[0073] By applying the technical solution of this embodiment, the fuel elements are first loaded into the honeycomb-shaped cells 31 of the porous plate 3. The upper and lower cladding plates 1 and 2 are then welded to the porous plate 3 to form the intermediate nuclear fuel. This effectively secures the fuel elements and prevents them from shifting or shaking during subsequent handling. The intermediate nuclear fuel is then subjected to a hot pressing and diffusion bonding process, which achieves a tight connection between the components and improves the bonding strength. Subsequently, a zirconium alloy β-phase heat treatment is performed to modify the microstructure of the zirconium alloy in the intermediate nuclear fuel, resulting in even better performance.

[0074] Furthermore, as a refinement and expansion of the specific implementation of the above embodiment, in order to fully illustrate the specific implementation process of this embodiment, another nuclear fuel preparation method is provided, see Figure 3 As shown, the method includes:

[0075] Step S201: preparing fuel elements;

[0076] Step S202: sandblasting the upper cladding plate 1 and the lower cladding plate 2;

[0077] Step S203: loading fuel elements into the honeycomb cells 31 of the porous plate 3, and welding the upper cladding plate 1, the lower cladding plate 2 and the porous plate 3 to form an intermediate nuclear fuel;

[0078] Step S204: hot pressing and diffusion bonding treatment of the intermediate nuclear fuel;

[0079] Step S205: heat treating the intermediate nuclear fuel in the zirconium alloy β phase;

[0080] Step S206: sandblasting the intermediate nuclear fuel.

[0081] In step S202, 0.3 MPa compressed air can be used as a power source to push 60# silicon carbide sand to sandblast the surfaces of the upper cladding plate 1 and the lower cladding plate 2. After the sandblasting is completed, the surfaces are immediately purged with high-purity argon gas to remove residual sand and other impurities.

[0082] In step S206, the intermediate nuclear fuel surface is sandblasted using the same blasting medium as in step S202: compressed air at a pressure of 0.3 MPa, using 60# silicon carbide sand. After the sandblasting process is complete, the intermediate nuclear fuel is first cleaned in a 10% hydrofluoric acid solution. The hydrofluoric acid reacts with residual surface impurities and some oxides, removing stubborn materials that are difficult to completely remove with sandblasting. Subsequently, the intermediate nuclear fuel is rinsed with hot deionized water to further remove the hydrofluoric acid solution and impurities generated by the reaction, thereby obtaining the target nuclear fuel that meets the cleanliness requirements.

[0083] Specifically, see Figure 4 As shown, Figure 4 The tensile curve of the interface between the upper cladding plate 1 and the lower cladding plate 2 and the fuel element at room temperature, the horizontal axis is engineering strain (Engineering Strain, unit: %), and the vertical axis is engineering stress (Engineering Stress, unit: MPa). Figure 4In the figure, the engineering stress-engineering strain relationship at room temperature between the upper cladding plate 1 and the lower cladding plate 2 of two nuclear fuels and the fuel element interface prepared under different conditions using the technical solution of this embodiment is shown. The nuclear fuel corresponding to curve 1 is prepared under the conditions of hot pressure parameters of 80MPa, treatment temperature of 750℃, treatment time of 1.5h during thermal diffusion bonding treatment, and treatment temperature of 950℃, treatment time of 8min during zirconium alloy β-phase heat treatment; the nuclear fuel corresponding to curve 2 is prepared under the conditions of hot pressure parameters of 120MPa, treatment temperature of 830℃, treatment time of 1.0h during thermal diffusion bonding treatment, and treatment temperature of 1010℃, treatment time of 3min during zirconium alloy β-phase heat treatment. From Figure 4 It can be seen that curve 1 and curve 2 are relatively close, indicating that the two nuclear fuels prepared under different conditions using the technical solution of this embodiment have good mechanical properties of the interfaces between the upper cladding plate 1 and the lower cladding plate 2 and the fuel elements when stretched at room temperature. That is, when subjected to tensile loads, the strength, ductility and other properties of the interfaces are similar, and both can well meet the requirements of the nuclear fuel for the mechanical properties of the interfaces, providing a reliable structural basis for the stable operation of the nuclear fuel in the reactor.

[0084] By applying the technical solution of this embodiment, the sandblasting treatment in step S202 effectively removes oil, rust, oxide layers, and other impurities from the surfaces of the upper and lower cladding plates 1 and 2. Furthermore, the sandblasting treatment creates a certain degree of surface roughness on the upper and lower cladding plates 1 and 2, increasing the contact area during welding and facilitating the mechanical engagement and metallurgical bonding between the welding material and the cladding plates. This improves the overall stability of the welded structure between the upper and lower cladding plates 1 and 2 and the porous plate 3, ensuring that the structure can withstand high temperatures, high pressures, and various complex stresses during nuclear reactor operation, and effectively preventing the risk of fuel leakage caused by welding problems. The sandblasting treatment in step S206 thoroughly removes oxide layers and impurities from the surface of the intermediate nuclear fuel, restoring the original material properties of the intermediate nuclear fuel surface, ensuring its excellent thermal conductivity and other physical and chemical properties, and ensuring the normal operation of the nuclear fuel in the reactor, maintaining the reactor's efficient and stable operation. At the same time, sandblasting can smooth the surface of the intermediate nuclear fuel, remove tiny bumps and depressions on the surface, and make the surface smoother and more uniform.

[0085] It is easy for those skilled in the art to understand that, under the premise of no conflict, the above-mentioned advantageous methods can be freely combined and superimposed.

[0086] The above are merely preferred embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application. The above are merely preferred embodiments of the present application. It should be noted that those skilled in the art may make various improvements and variations without departing from the technical principles of the present application, and such improvements and variations shall also be considered within the scope of protection of the present application.

Claims

1. A nuclear fuel, characterized in that: include: Upper and lower cladding plates arranged opposite to each other; A porous plate disposed between the upper cladding plate and the lower cladding plate, wherein the porous plate has a honeycomb structure, and the honeycomb structure forms a plurality of honeycomb compartments; A fuel element is arranged in each of the honeycomb cells, the upper surface of the fuel element contacts the upper cladding plate, the lower surface of the fuel element contacts the lower cladding plate, and the outer peripheral surface of the fuel element contacts the wall of the honeycomb cell.

2. The nuclear fuel according to claim 1, characterized in that The upper surface, the lower surface and the peripheral surface of the fuel element are all provided with a diffusion barrier layer, and the diffusion barrier layer is a graphite coating or a metal chromium coating.

3. The nuclear fuel according to claim 1, characterized in that The upper cladding plate, the lower cladding plate and the porous plate are all made of zirconium alloy. The thickness of the upper cladding plate and the lower cladding plate is 0.2-0.8 mm, and the thickness of the porous plate is 1.0-2.0 mm.

4. A method for preparing nuclear fuel, characterized in that: For preparing the nuclear fuel according to any one of claims 1 to 3, the method comprises: preparing the fuel element; Loading the fuel elements into the honeycomb compartments of the porous plate, and welding the upper cladding plate, the lower cladding plate, and the porous plate to form intermediate nuclear fuel; Hot-pressing, diffusion-bonding treatment of the intermediate nuclear fuel; The intermediate nuclear fuel is heat treated in a zirconium alloy beta phase.

5. The nuclear fuel preparation method according to claim 4, characterized in that: The preparation of the fuel element comprises: Mixing ceramic phase raw material particles and metal matrix material powder to form a mixed powder system; Filling the mixed powder system into a mold and hot pressing it into shape; Wherein, the volume content of the ceramic phase raw material particles in the mixed powder system does not exceed 30%.

6. The nuclear fuel preparation method according to claim 4, characterized in that: The preparation of the fuel element comprises: Ceramic phase raw material particles and metal matrix material powder are loaded into the mold layer by layer and hot pressed into shape.

7. The nuclear fuel preparation method according to claim 4, characterized in that: When the intermediate nuclear fuel is treated by hot-pressing diffusion bonding, the hot-pressing parameter is 80-150 MPa, the treatment temperature is 750-830° C., and the treatment time is 1-2 hours.

8. The nuclear fuel preparation method according to claim 4, characterized in that: When the intermediate nuclear fuel is heat-treated in the zirconium alloy β phase, the treatment temperature is 950-1010° C. and the treatment time is 3-10 minutes.

9. The nuclear fuel preparation method according to claim 4, characterized in that: Before loading the fuel elements into the honeycomb cells of the porous plate, the method further comprises: The upper cladding cover plate and the lower cladding cover plate are subjected to sandblasting.

10. The nuclear fuel preparation method according to claim 4, characterized in that: After heat treating the intermediate nuclear fuel in the zirconium alloy β phase, the method further comprises: The intermediate nuclear fuel is sandblasted.

Images