Preparation method of uranium nitride pellet fuel and uranium nitride pellet fuel

Abstract

The embodiment of the invention relates to the technical field of binary compounds of nitrogen and metal, in particular to a preparation method of uranium nitride pellet fuel and the uranium nitride pellet fuel. The invention provides a preparation method of uranium nitride pellet fuel, which comprises the following steps: treating molybdenum-niobium metal powder to coat a zirconium coating on the molybdenum-niobium metal powder; preparing uranium oxide particles with uniform particle size; the uranium oxide particles react with ammonia gas, and uranium nitride particles are obtained; molybdenum-niobium alloy powder and uranium nitride particles are mixed, and the molybdenum-niobium alloy powder and the uranium nitride particles are evenly distributed in the obtained mixture; sintering the mixture to enable the obtained pellet to form a compact structure; and molding the pellet to obtain the uranium nitride pellet fuel. The invention further provides the uranium nitride pellet fuel. According to the method for preparing the fuel, on the premise that efficient combustion of the fuel can be guaranteed, the damage resistance of the fuel under the intense radiation condition can be improved, irradiation swelling of the fuel is reduced, the low release property of the fuel is guaranteed, and the application requirement in a space nuclear reactor is fully met.

Description

Technical Field

[0001] The embodiments of the present application relate to the technical field of binary compounds of nitrogen and metals, and specifically to a preparation method of uranium nitride particle fuel and uranium nitride particle fuel. Background Art

[0002] The statements herein merely provide background information related to the present application and do not necessarily constitute prior art.

[0003] A space special reactor is a nuclear reactor that uses the energy generated by nuclear fission to provide energy for space vehicles. As an important energy equipment for future space activities, it needs to operate stably for a long time in extreme environments. This places extremely high performance requirements on the nuclear fuel serving in the nuclear reactor. For example, the nuclear fuel needs to have stable physical and chemical properties under high temperature conditions, high radiation resistance, high thermal conductivity, and low release.

[0004] However, nuclear fuel prepared using traditional nuclear fuel preparation methods has many defects in performance tests of space special reactors and is difficult to meet the performance requirements for use in the special service environment of space special reactors. Summary of the Invention

[0005] A brief overview of the present application is provided below to provide a basic understanding of certain aspects of the present application. It should be understood that this overview is not an exhaustive overview of the present application. It is not intended to identify key or important portions of the present application, nor is it intended to limit the scope of the present application. Its purpose is simply to present certain concepts in a simplified form as a prelude to the more detailed description that will be discussed later.

[0006] In a first aspect, an embodiment of the present application provides a method for preparing uranium nitride pellet fuel, comprising the following steps: S10: processing raw molybdenum and niobium metal powders to coat the obtained molybdenum-niobium alloy powder with a zirconium coating; S20: preparing uranium oxide particles with uniform particle size; S30: placing the uranium oxide particles in a reaction area, introducing ammonia gas into the reaction area, causing the uranium oxide particles to react with the ammonia gas, and obtaining low-density uranium nitride particles with uniform particle size; S40: mixing the molybdenum-niobium alloy powder obtained in step S10 with the uranium nitride particles obtained in step S30, so that the molybdenum-niobium alloy powder and the uranium nitride particles are evenly distributed in the obtained mixture; S50: sintering the mixture to combine the molybdenum-niobium alloy powder and the uranium nitride particles, so that the obtained pellets form a dense structure; S60: shaping the pellets to obtain uranium nitride pellet fuel.

[0007] In a second aspect, an embodiment of the present application provides a uranium nitride particle fuel, which is prepared using the preparation method of any embodiment of the first aspect of the present application.

[0008] The method in the embodiments of the present application prepares molybdenum and niobium metal powders coated with a zirconium coating, and uses them as matrix materials to ensure compatibility with uranium nitride particles, which is beneficial to improving the thermal conductivity and high-temperature stability of the prepared uranium nitride particle fuel; prepares low-density uranium nitride particles with uniform particle size to optimize their surface structure and improve the bonding strength with the matrix material; and mixes the matrix material and uranium nitride particles until the two are evenly distributed in the mixture to ensure that the low-density uranium nitride particles are uniformly dispersed in the matrix material, and then sinters the mixture into a dense structure and shapes it to further improve the density and uniformity of the fuel. Therefore, while ensuring that the fuel can burn efficiently, the damage resistance of the fuel under strong radiation conditions is significantly improved, the radiation swelling of the fuel is reduced, and the low release of the fuel is ensured, fully meeting the application requirements in special nuclear reactors in space. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Other objects and advantages of the present application will become apparent from the following description of the embodiments of the present application with reference to the accompanying drawings, which will help to provide a comprehensive understanding of the present application.

[0010] Figure 1 4 is a flow chart of a method for preparing uranium nitride particle fuel according to an embodiment of the present application.

[0011] It should be noted that the drawings are not necessarily drawn to scale, but are merely shown in a schematic manner that does not affect the reader's understanding. DETAILED DESCRIPTION

[0012] Exemplary embodiments of the present application will be described below with reference to the accompanying drawings. For the sake of clarity and conciseness, not all features of actual implementations are described in the specification. However, it should be understood that many implementation-specific decisions must be made in the process of developing any such actual implementation in order to achieve the developer's specific goals, such as meeting those constraints related to the system and business, and these constraints may vary depending on the implementation. In addition, it should be understood that although the development work may be very complex and time-consuming, it is a routine task for those skilled in the art who benefit from the content of this application.

[0013] It is also necessary to explain here that, in order to avoid obscuring the present application due to unnecessary details, the accompanying drawings only show the device structure and / or processing steps that are closely related to the solution according to the present application, while other details that are not closely related to the present application are omitted.

[0014] The inventors of this application have discovered that the nuclear fuel prepared using existing methods has problems with high-temperature stability, radiation resistance, and thermal conductivity that cannot meet predetermined requirements in application performance tests of special space nuclear reactors. This can easily lead to fuel melting or structural collapse, resulting in relatively serious radiation damage, making it difficult to ensure the integrity of the fuel, and making it unsuitable for use in the extreme service environment of space nuclear reactors.

[0015] Based on this, the embodiment of the present application provides a method for preparing uranium nitride particle fuel, such as Figure 1 As shown, Figure 1 A flow chart showing a method for preparing uranium nitride particle fuel according to an embodiment of the present application is provided, which includes the following steps S10 to S60:

[0016] S10: Processing raw material molybdenum and niobium metal powders to coat the obtained molybdenum-niobium alloy powder with a zirconium coating.

[0017] S20: preparing uranium oxide particles with uniform particle size.

[0018] S30: placing uranium oxide particles in a reaction area, introducing ammonia gas into the reaction area, and causing the uranium oxide particles to react with the ammonia gas to obtain low-density uranium nitride particles with uniform particle size.

[0019] S40: mixing the molybdenum-niobium alloy powder obtained in step S10 with the uranium nitride particles obtained in step S30, so that the molybdenum-niobium alloy powder and the uranium nitride particles are evenly distributed in the obtained mixture.

[0020] S50: Sintering the mixture to combine the molybdenum-niobium alloy powder and the uranium nitride particles so that the obtained pellets form a dense structure.

[0021] S60: Molding the pellets to obtain uranium nitride particle fuel.

[0022] The fuel preparation method provided in the embodiments of the present application prepares molybdenum and niobium metal powders coated with a zirconium coating, which are used as matrix materials to ensure compatibility with uranium nitride particles, thereby improving the thermal conductivity and high-temperature stability of the prepared uranium nitride particle fuel; prepares low-density uranium nitride particles with uniform particle size to optimize their surface structure and improve the bonding strength with the matrix material; and mixes the matrix material and uranium nitride particles until the two are evenly distributed in the mixture to ensure that the low-density uranium nitride particles are evenly dispersed in the matrix material. The mixture is then sintered into a dense structure and formed to further improve the density and uniformity of the fuel. Thus, while ensuring that the fuel can burn efficiently, the damage resistance of the fuel under strong radiation conditions is significantly improved, the radiation swelling of the fuel is reduced, and the low release of the fuel is ensured, fully meeting the application requirements in special nuclear reactors in space.

[0023] In some embodiments, step S10 further includes the following steps:

[0024] S11: Add ZrCl4 to the raw material molybdenum and niobium metal powders and place them in the reaction area.

[0025] S12: hydrogen is introduced into the reaction area at a predetermined rate.

[0026] S13: The reaction area is heated to a predetermined temperature to allow the raw materials, molybdenum and niobium metal powders, to react with ZrCl4 and hydrogen for a predetermined time.

[0027] In this embodiment, a zirconium oxide precursor and hydrogen gas are used as a reducing agent. Molybdenum and niobium metal powders coated with a zirconium coating are obtained by reacting raw molybdenum and niobium metal powders with zirconium oxide and hydrogen gas at a predetermined temperature and for a predetermined time. The zirconium coating is used to delay the reaction between the molybdenum and niobium metal powders as the base material and the uranium nitride particles, thereby ensuring compatibility with the uranium nitride particles and significantly improving the thermophysical properties of the prepared uranium nitride particle fuel, so that it has high thermal conductivity and good high-temperature stability.

[0028] Specifically, in step S10, molybdenum and niobium metal powders with a purity of 99.99% and a particle size of 2-5 μm are used as raw molybdenum and niobium metal powders, a ZrCl4 precursor is added to the raw molybdenum and niobium metal powders, and the raw materials are placed in a reaction zone. Hydrogen is introduced into the reaction zone at a rate of 20-50 ml / min, and the reaction zone is heated to a temperature range of 800-1200° C. The raw molybdenum and niobium metal powders are reacted with ZrCl4 and hydrogen for 0.5-2 hours to obtain molybdenum and niobium metal powders coated with a uniform and dense zirconium coating, thereby ensuring the quality of the base material and further improving the compatibility of the base material with the uranium nitride particles.

[0029] In some embodiments, step S20 further includes the following steps:

[0030] S21: Prepare uranyl nitrate solution.

[0031] S22: Stir the uranyl nitrate solution to convert it into a sol.

[0032] S23: adding an alkaline substance to the sol to cause the sol to condense.

[0033] S24: vibrating the sol, and controlling the vibration frequency and amplitude to make the particle size of the obtained uranium oxide particles uniform.

[0034] In this embodiment, a uranyl nitrate solution is stirred to convert it into a sol, an alkaline substance is added to the sol to condense the sol, and the sol is subjected to a vibration treatment to regulate the porosity of the prepared spherical uranium oxide particles, which is beneficial for the subsequent preparation of low-density uranium nitride particles. In addition, the presence of pores can reduce the reaction between the uranium nitride particles and the matrix material, thereby improving the compatibility of the uranium nitride particles with the matrix material.

[0035] Specifically, in step S20, a uranyl nitrate solution is prepared, urea (CO(NH2)2) is used as an organic complexing agent, the uranium concentration in the uranyl nitrate solution is adjusted to 0.1-0.5 mol / L, and the pH value of the uranyl nitrate solution is adjusted to 2.0-3.0; the uranyl nitrate solution is stirred at a speed of 500-1000 rpm for 1-2 hours in a temperature range of 20-30°C to convert it into a sol; an alkaline substance, such as ammonia water, is added to the sol to increase the pH value of the sol to 8.0-10.0 to promote sol coagulation; the sol is vibrated, the vibration frequency is controlled at 50-100 Hz, and the amplitude is controlled at 1-2 mm, so as to obtain low-density uranium oxide particles with a particle diameter in the range of 50-500 μm and a uniform particle size distribution, thereby facilitating the subsequent preparation of low-density uranium nitride particles with uniform particle size.

[0036] In some embodiments, prior to step S24, the sol is heated in a water bath to accelerate colloid aggregation and sedimentation, thereby slowing down the change in the nucleation size of the uranium oxide fuel and facilitating the formation of uranium oxide particles with uniform particle size. For example, the water bath heating temperature can be set within a range of 50-80°C.

[0037] In some embodiments, step S30 further includes the following steps:

[0038] S31: A nitrogen-hydrogen mixed gas is introduced into the reaction area to form a nitrogen-hydrogen atmosphere in the reaction area.

[0039] S32: placing the uranium oxide particles obtained in step S20 in a reaction area.

[0040] S33: Ammonia gas is introduced into the reaction region at a predetermined rate, and the reaction region is heated to a predetermined temperature, so that the uranium oxide particles react with the ammonia gas for a predetermined time.

[0041] In this embodiment, uranium oxide particles are placed in a nitrogen-hydrogen atmosphere, and ammonia gas is introduced into the reaction region at a predetermined rate during the heating process. The uranium oxide particles react with the ammonia gas for a predetermined time to increase the nitridation reaction rate, slow down the pore closure process of the uranium oxide particles, facilitate control of the particle size, and facilitate the formation of low-density uranium nitride particles with uniform particle size, thereby optimizing their surface structure and improving their bonding with the molybdenum-niobium matrix material.

[0042] In some embodiments, in step S31, the volume ratio of H2:NH3 in the nitrogen-hydrogen atmosphere formed in the reaction area is 1:9. Using a higher volume ratio of NH3 can accelerate the nitriding reaction process and facilitate the formation of uranium nitride particles with uniform particle size distribution.

[0043] In some embodiments, in step S33, ammonia gas is introduced into the reaction region at a rate of 0.5-1.0 L / min, and the reaction region is heated to 800-1000° C., allowing the uranium oxide particles and ammonia gas to react for 2-4 hours. In this embodiment, a moderate flow rate is employed to ensure sufficient contact between the ammonia gas and the uranium oxide particles, preventing localized reactions from being too rapid or too slow, thereby improving reaction uniformity. Furthermore, the high temperature of 800-1000° C. facilitates sufficient reaction between the ammonia gas and the uranium oxide particles, ensuring the quality of the target uranium nitride particles produced.

[0044] In some embodiments, step S40 further includes the following steps:

[0045] S41: placing the molybdenum-niobium alloy powder obtained in step S10 and the uranium nitride particles obtained in step S30 in a mixing area according to a predetermined ratio.

[0046] S42: The mixing area is vibrated at a predetermined frequency for a predetermined time, while argon gas is introduced into the mixing area at a predetermined speed.

[0047] In this embodiment, molybdenum-niobium alloy powder and uranium nitride particles are placed in a mixing area according to a predetermined ratio, vibrated at a predetermined frequency for a predetermined time, and argon gas is introduced into the mixing area at a predetermined speed using airflow assistance. Since the vibration force used is much lower than the material strength, damage to the structure of the uranium nitride particles caused by mixing using a traditional ball milling process can be avoided, thereby ensuring the surface structural integrity of the uranium nitride particles and improving their bonding with the molybdenum-niobium alloy powder matrix material.

[0048] In some embodiments, in step S41, the molybdenum-niobium alloy powder obtained in step S10 and the uranium nitride particles obtained in step S30 are placed in a mixing area in a ratio of 5:1; in step S42, the mixture is vibrated at a frequency of 50-100 Hz for 1-3 hours, and argon gas is introduced into the mixing area at a speed of 10-20 m / s to uniformly mix the molybdenum-niobium alloy powder and the uranium nitride particles without damaging the structure of the uranium nitride particles, thereby ensuring that the low-density uranium nitride particles are uniformly dispersed in the molybdenum-niobium alloy powder matrix material.

[0049] In some embodiments, in step S42, vibration forces in different directions may be applied to the mixing region at a predetermined frequency to further improve the mixing effect and achieve homogenization of the molybdenum-niobium alloy powder and the uranium nitride particle material.

[0050] In some embodiments, step S50 further includes the following steps:

[0051] S51: placing the mixture obtained in step S40 in a sintering area.

[0052] S52: Inert gas is introduced into the sintering area.

[0053] S53: Controlling the temperature of the sintering region, the pressure applied to the sintering region, and the discharge energy to combine the molybdenum-niobium alloy powder and the uranium nitride particles.

[0054] In this embodiment, the mixture is sintered under inert gas protection to prevent oxidation of the uranium nitride particles during high-temperature sintering. The temperature of the sintering zone, the pressure applied to the sintering zone, and the discharge energy are controlled to achieve densification of the uranium nitride. This facilitates the sintering of the molybdenum-niobium alloy powder and the uranium nitride particles into a preliminary dense structure.

[0055] In some embodiments, in step S53, the temperature of the sintering zone is controlled between 1600-1800° C., the pressure applied to the sintering zone is controlled between 50-100 MPa, and the discharge energy is controlled between 500-1000 A, so as to effectively promote the diffusion and bonding of the molybdenum-niobium alloy powder and the uranium nitride particles, reduce the porosity of the uranium nitride particles, form a uniform and dense pellet structure, and at the same time, avoid component segregation and material oxidation caused by high temperature, thereby improving the quality of the obtained pellet structure.

[0056] In some embodiments, in step S60, the pellets obtained in step S50 are subjected to hot extrusion treatment to further eliminate pores inside the pellets, enhance the density and uniformity of the pellets, and ultimately obtain high-density and high-quality molybdenum-niobium matrix dispersed low-density uranium nitride particle fuel.

[0057] Specifically, in step S60, the pellets obtained in step S50 are hot extruded at a temperature range of 1800-2000° C., a high pressure of 100-200 MPa, and a pressure holding time of 30-90 minutes to eliminate pores inside the pellets and promote grain reorganization, thereby improving the density, mechanical properties, and uniformity of the generated uranium nitride pellet fuel, further ensuring that high-quality uranium nitride pellet fuel is ultimately obtained.

[0058] An embodiment of the present application further provides a uranium nitride particle fuel, which is prepared using the preparation method of any embodiment of the first aspect of the present application.

[0059] The preparation process of the uranium nitride particle fuel in this application is further described below.

[0060] Molybdenum and niobium metal powders with a purity of 99.99% and a particle size of 2-5 μm are used as raw molybdenum and niobium metal powders. A ZrCl4 precursor is added to the raw molybdenum and niobium metal powders, and the powders are placed in a reaction area. Hydrogen is introduced into the reaction area at a rate of 20-50 ml / min. The reaction area is heated to a temperature range of 800-1200° C., and the raw molybdenum and niobium metal powders are reacted with ZrCl4 and hydrogen for 0.5-2 hours to obtain a molybdenum-niobium alloy powder coated with a zirconium coating. The method comprises the following steps: preparing a uranyl nitrate solution, using urea (CO(NH2)2) as an organic complexing agent, adjusting the uranium concentration in the uranyl nitrate solution to 0.1-0.5 mol / L, and adjusting the pH value of the uranyl nitrate solution to 2.0-3.0; stirring the uranyl nitrate solution at a speed of 500-1000 rpm for 1-2 hours in a temperature range of 20-30°C to convert it into a sol; adding ammonia water to the sol to increase the pH value of the sol to 8.0-10.0 to cause the sol to condense; heating the sol in a water bath in a temperature range of 50-80°C to accelerate the aggregation and sedimentation of the colloid; and vibrating the sol, controlling the vibration frequency to 50-100 Hz and the amplitude to 1-2 mm, to obtain uranium oxide particles with a particle diameter in the range of 50-500 μm and a uniform particle size distribution. A nitrogen-hydrogen mixture is introduced into the reaction zone to form a nitrogen-hydrogen atmosphere with a volume ratio of H2:NH3 of 1:9. Uranium oxide particles are placed in the reaction zone. Ammonia gas is introduced into the reaction zone at a rate of 0.5-1.0 L / min, and the reaction zone is heated to 800-1000°C to allow the uranium oxide particles to react with the ammonia gas for 2-4 hours to obtain low-density uranium nitride particles with uniform particle size. Molybdenum-niobium alloy powder and uranium nitride particles are placed in a mixing zone at a ratio of 5:1. The mixture is vibrated at a frequency of 50-100 Hz for 1-3 hours while argon gas is introduced into the mixing zone at a rate of 10-20 m / s to obtain a uniform mixture of the two. The mixture is placed in a sintering area, where an inert gas is introduced. The temperature in the sintering area is controlled between 1600-1800°C, the pressure applied to the sintering area is controlled between 50-100 MPa, and the discharge energy is controlled between 500-1000A, thereby combining the molybdenum-niobium alloy powder and the uranium nitride particles to form a dense pellet. The pellet is then hot-extruded at a temperature of 1800-2000°C, a high pressure of 100-200 MPa, and a holding pressure of 30-90 minutes to produce uranium nitride pellet fuel.

[0061] Regarding the embodiments of the present application, it should also be noted that, in the absence of conflict, the embodiments of the present application and the features therein can be combined with each other to obtain new embodiments.

[0062] The above are only specific implementation methods of the present application, but the protection scope of the present application is not limited thereto. The protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. A method for preparing uranium nitride particle fuel, characterized in that: It includes the following steps: S10: processing raw molybdenum and niobium metal powders to coat the obtained molybdenum-niobium alloy powder with a zirconium coating; S20: preparing uranium oxide particles with uniform particle size; S30: placing the uranium oxide particles in a reaction area, introducing ammonia gas into the reaction area, causing the uranium oxide particles to react with the ammonia gas, and obtaining low-density uranium nitride particles with uniform particle size; S40: mixing the molybdenum-niobium alloy powder obtained in step S10 with the uranium nitride particles obtained in step S30, so that the molybdenum-niobium alloy powder and the uranium nitride particles are evenly distributed in the obtained mixture; S50: sintering the mixture to combine the molybdenum-niobium alloy powder and the uranium nitride particles, so that the obtained pellets form a dense structure; S60: shaping the pellets to obtain the uranium nitride particle fuel.

2. The method according to claim 1, characterized in that In step S10, the following steps are also included: S11: adding ZrCl4 to the raw material molybdenum and niobium metal powders and placing them in a reaction area; S12: Inputting hydrogen into the reaction area at a predetermined rate; S13: heating the reaction region to a predetermined temperature, so that the raw materials of molybdenum and niobium metal powder react with the ZrCl 4 and the hydrogen for a predetermined time.

3. The method according to claim 1, characterized in that In step S20, the following steps are also included: S21: preparing uranyl nitrate solution; S22: stirring the uranyl nitrate solution to convert it into a sol; S23: adding an alkaline substance to the sol to cause the sol to condense; S24: vibrating the sol, and controlling the vibration frequency and amplitude to make the particle size of the obtained uranium oxide particles uniform.

4. The method according to claim 3, characterized in that Before step S24, the sol is heated in a water bath to accelerate the aggregation and sedimentation of the colloid.

5. The method according to claim 1, characterized in that In step S30, the following steps are also included: S31: introducing a nitrogen-hydrogen mixed gas into the reaction region to form a nitrogen-hydrogen atmosphere in the reaction region; S32: placing the uranium oxide particles obtained in step S20 in the reaction area; S33: introducing ammonia gas into the reaction region at a predetermined rate, and heating the reaction region to a predetermined temperature, so that the uranium oxide particles react with the ammonia gas for a predetermined time.

6. The method according to claim 5, characterized in that In step S33, ammonia gas is introduced into the reaction region at a rate of 0.5-1.0 L / min, and the reaction region is heated to 800-1000° C. to allow the uranium oxide particles to react with the ammonia gas for 2-4 hours.

7. The method according to claim 1, characterized in that In step S40, the following steps are also included: S41: placing the molybdenum-niobium alloy powder obtained in step S10 and the uranium nitride particles obtained in step S30 in a mixing area according to a predetermined ratio; S42: vibrating the mixing region at a predetermined frequency for a predetermined time, while introducing argon gas into the mixing region at a predetermined speed.

8. The method according to claim 1, characterized in that In step S50, the following steps are also included: S51: placing the mixture obtained in step S40 in a sintering area; S52: introducing an inert gas into the sintering area; S53: controlling the temperature of the sintering region, the pressure applied to the sintering region, and the discharge energy to combine the molybdenum-niobium alloy powder with the uranium nitride particles.

9. The method according to claim 8, characterized in that In step S53, the temperature of the sintering area is controlled between 1600-1800°C, the pressure applied to the sintering area is controlled between 50-100 MPa, and the discharge energy is controlled between 500-1000A.

10. The method according to claim 1, characterized in that In step S60, the core block obtained in step S50 is subjected to hot extrusion treatment.

11. A uranium nitride particle fuel, characterized in that: The uranium nitride particle fuel is prepared by the preparation method according to any one of claims 1 to 10.

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