Process for the production of uranium nitride particulate fuel and uranium nitride particulate fuel

Abstract

The embodiment of the application relates to the technical field of binary compounds of nitrogen and metal, and particularly relates to a preparation method of uranium nitride particle fuel and the uranium nitride particle fuel. The application provides a preparation method of uranium nitride particle fuel, which comprises the following steps: treating molybdenum-niobium metal powder, so that the molybdenum-niobium alloy powder is coated with a zirconium coating; preparing uranium oxide particles with uniform particle size; reacting the uranium oxide particles with ammonia to obtain uranium nitride particles; mixing the molybdenum-niobium alloy powder and the uranium nitride particles, so that the two are uniformly distributed in the obtained mixture; sintering the mixture, so that the obtained compact is formed into a dense structure; and forming the compact to obtain the uranium nitride particle fuel. The application also provides a uranium nitride particle fuel. The fuel prepared by the method of the application can improve the damage resistance of the fuel under strong radiation conditions, reduce the irradiation swelling of the fuel, ensure the low release of the fuel, and fully meet the application requirements in space nuclear reactors.

Description

Technical Field

[0001] The embodiments of this application relate to the field of binary compounds of nitrogen and metals, specifically to a method for preparing uranium nitride particulate fuel and uranium nitride particulate fuel. Background Technology

[0002] The statements herein are provided merely as background information in connection with this application and do not necessarily constitute prior art.

[0003] Space-specific reactors are nuclear reactors that use the energy generated by nuclear fission to power spacecraft. As an important energy device for future space activities, they need to operate stably for a long time in extreme environments. This places extremely high performance requirements on the nuclear fuel used in the 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] Nuclear fuel prepared using traditional nuclear fuel preparation methods has many defects in performance tests of special space reactors, making it difficult to meet the performance requirements for use in the special service environment of special space reactors. Summary of the Invention

[0005] A brief overview of this application is provided below to offer a basic understanding of certain aspects thereof. It should be understood that this overview is not an exhaustive summary of the application. It is not intended to identify key or essential parts of the application, nor is it intended to limit its scope. Its purpose is merely to present certain concepts in a simplified form as a prelude to the more detailed description that follows.

[0006] In a first aspect, embodiments of this application provide a method for preparing uranium nitride pellet fuel, comprising the following steps: S10: processing raw material molybdenum and niobium metal powders to coat the obtained molybdenum-niobium alloy powder with a zirconium coating; S20: preparing uranium oxide pellets with uniform particle size; S30: placing the uranium oxide pellets in a reaction zone and introducing ammonia gas into the reaction zone to react the uranium oxide pellets with the ammonia gas to obtain low-density uranium nitride pellets with uniform particle size; S40: mixing the molybdenum-niobium alloy powder obtained in step S10 with the uranium nitride pellets obtained in step S30 to ensure that both are uniformly distributed in the obtained mixture; S50: sintering the mixture to combine the molybdenum-niobium alloy powder with the uranium nitride pellets to form a dense structure in the obtained pellet; S60: molding the pellet to obtain uranium nitride pellet fuel.

[0007] Secondly, embodiments of this application provide a uranium nitride particulate fuel, which is prepared using the preparation method of any embodiment of the first aspect of this application.

[0008] The method in the embodiments of this application prepares molybdenum and niobium metal powder coated with zirconium to ensure compatibility with uranium nitride particles as a matrix material, which is beneficial to improving the thermal conductivity and high-temperature stability of the prepared uranium nitride particle fuel. It also optimizes the surface structure of the uranium nitride particles by preparing uniformly sized, low-density particles, thereby improving their bonding strength with the matrix material. Furthermore, it mixes the matrix material and uranium nitride particles until they are uniformly distributed in the mixture, ensuring that the low-density uranium nitride particles are uniformly dispersed in the matrix material. Finally, it sinterstens the mixture into a dense structure and shapes it to further improve the density and uniformity of the fuel. Thus, while ensuring efficient combustion, it significantly improves the fuel's resistance to damage under strong radiation conditions, reduces fuel irradiation swelling, ensures low fuel release, and fully meets the application requirements in special space nuclear reactors. Attached Figure Description

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

[0010] Figure 1 This is a flowchart of a method for preparing uranium nitride particulate fuel according to an embodiment of this application.

[0011] It should be noted that the accompanying drawings are not necessarily drawn to scale, but are shown only in a schematic manner without affecting the reader's understanding. Detailed Implementation

[0012] Exemplary embodiments of this application will be described below with reference to the accompanying drawings. For clarity and brevity, 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 development of any such actual embodiment to achieve the developer's specific goals, such as complying with constraints related to the system and business, and these constraints may vary depending on the implementation. Furthermore, it should be understood that while development work can be very complex and time-consuming, such development work is merely a routine task for those skilled in the art who benefit from the content of this application.

[0013] It should also be noted that, in order to avoid obscuring this application with unnecessary details, only the equipment structure and / or processing steps closely related to the solution according to this application are shown in the accompanying drawings, while other details that are not closely related to this application are omitted.

[0014] The inventors of this application have discovered that nuclear fuel prepared using existing methods has problems in high-temperature stability, radiation resistance, and thermal conductivity that fail to meet predetermined requirements during application performance tests of special space nuclear reactors. This can easily lead to fuel melting or structural collapse, resulting in severe radiation damage, making it difficult to ensure fuel integrity, and thus unsuitable for the extreme service environment of space nuclear reactors.

[0015] Based on this, embodiments of this application provide a method for preparing uranium nitride particulate fuel, such as... Figure 1 As shown, Figure 1 A flowchart illustrating a method for preparing uranium nitride particulate fuel according to an embodiment of this application is provided, comprising the following steps S10 to S60:

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

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

[0018] S30: Place uranium oxide particles in the reaction zone and introduce ammonia gas into the reaction zone to react the uranium oxide particles with the ammonia gas, thereby obtaining low-density uranium nitride particles with uniform particle size.

[0019] S40: Mix the molybdenum-niobium alloy powder obtained in step S10 with the uranium nitride particles obtained in step S30 to make both uniformly distributed in the resulting mixture.

[0020] S50: Sintering mixture, which combines molybdenum-niobium alloy powder with uranium nitride particles to form a dense structure in the resulting core.

[0021] S60: To form pellets and obtain uranium nitride particulate fuel.

[0022] The fuel preparation method provided in this application prepares molybdenum and niobium metal powder coated with zirconium to ensure compatibility with uranium nitride particles as a matrix material, thereby improving the thermal conductivity and high-temperature stability of the prepared uranium nitride particle fuel. It also prepares low-density uranium nitride particles with uniform particle size to optimize their surface structure and improve their bonding with the matrix material. Furthermore, it mixes the matrix material and uranium nitride particles until they are uniformly distributed in the mixture, ensuring uniform dispersion of the low-density uranium nitride particles within the matrix material. Finally, it sinterstens the mixture into a dense structure and shapes it to further improve the fuel's density and uniformity. Thus, while ensuring efficient combustion, it significantly improves the fuel's resistance to damage under strong radiation conditions, reduces irradiation swelling, ensures low fuel release, and fully meets the application requirements in space-specific nuclear reactors.

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

[0024] S11: Add ZrCl4 to the raw material molybdenum and niobium metal powder and place it in the reaction zone.

[0025] S12: Introduce hydrogen into the reaction zone at a predetermined rate.

[0026] S13: Heat the reaction zone 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 is used, and hydrogen is used as a reducing agent. By reacting raw material molybdenum and niobium metal powder with zirconium oxide and hydrogen at a predetermined temperature for a predetermined time, molybdenum and niobium metal powder coated with zirconium is obtained. The zirconium coating is used to delay the reaction between the molybdenum and niobium metal powder, which serves as the matrix material, and uranium nitride particles, thereby ensuring compatibility with uranium nitride particles and significantly improving the thermophysical properties of the prepared uranium nitride particle fuel, giving it high thermal conductivity and good high-temperature stability.

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

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

[0030] S21: Prepare uranyl nitrate solution.

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

[0032] S23: Add an alkaline substance to the sol to cause it to coagulate.

[0033] S24: Vibrate the sol and control the vibration frequency and amplitude to make the obtained uranium oxide particles uniform in size.

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

[0035] Specifically, in step S20, a uranyl nitrate solution is prepared by using urea (CO(NH2)2) as an organic composite agent to achieve a uranium concentration of 0.1-0.5 mol / L in the uranyl nitrate solution and adjusting the pH value of the solution to 2.0-3.0. The uranyl nitrate solution is stirred at 500-1000 rpm for 1-2 hours within a temperature range of 20-30℃ to convert it into a sol. An alkaline substance, such as ammonia, is added to the sol to raise its pH value to 8.0-10.0, promoting sol coagulation. The sol is then subjected to vibration treatment, with the vibration frequency controlled at 50-100 Hz and the amplitude controlled at 1-2 mm, to obtain low-density uranium oxide particles with a particle diameter in the range of 50-500 μm and a uniform particle size distribution. This facilitates 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 its aggregation and sedimentation, thereby slowing down the change in 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 in the range of 50-80°C.

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

[0038] S31: Introduce a nitrogen-hydrogen mixture into the reaction zone to create a nitrogen-hydrogen atmosphere in the reaction zone.

[0039] S32: Place the uranium oxide particles obtained in step S20 into the reaction zone.

[0040] S33: Ammonia gas is introduced into the reaction zone at a predetermined rate, and the reaction zone 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 zone at a predetermined rate during heating. This allows the uranium oxide particles to react with the ammonia gas for a predetermined time, thereby increasing the nitriding reaction rate, slowing down the pore closure process of the uranium oxide particles, facilitating particle size control, and promoting the formation of low-density uranium nitride particles with uniform particle size. This optimizes the surface structure and improves the bonding force with the molybdenum-niobium matrix material.

[0042] In some embodiments, in step S31, the volume ratio of H2 to NH3 in the nitrogen-hydrogen atmosphere formed in the reaction region is 1:9. Using a higher NH3 volume ratio 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 zone at a rate of 0.5-1.0 L / min, and the reaction zone is heated to 800-1000°C, allowing the uranium oxide particles to react with the ammonia gas for 2-4 hours. In this embodiment, a moderate flow rate is used to ensure sufficient contact between the ammonia gas and the uranium oxide particles, avoiding excessively fast or slow local reactions, thereby improving the uniformity of the reaction. Furthermore, the high-temperature environment of 800-1000°C is conducive to the full reaction of ammonia gas and uranium oxide particles, ensuring the quality of the generated target product, uranium nitride particles.

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

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

[0046] S42: Vibrate the mixing region at a predetermined frequency for a predetermined time, while simultaneously introducing argon gas into the mixing region at a predetermined speed.

[0047] In this embodiment, molybdenum-niobium alloy powder and uranium nitride particles are placed in a mixing zone according to a predetermined ratio and vibrated at a predetermined frequency for a predetermined time. At the same time, argon gas is introduced into the mixing zone at a predetermined speed with airflow assistance. Since the vibration force used is much lower than the material strength, the damage to the structure of uranium nitride particles caused by the traditional ball milling process can be avoided, ensuring the integrity of the surface structure of the uranium nitride particles, thereby improving its bonding force 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 region at a ratio of 5:1; in step S42, the mixture is vibrated at a vibration frequency of 50-100Hz for 1-3 hours, while argon gas is introduced into the mixing region at a speed of 10-20m / s, so as to make the molybdenum-niobium alloy powder and the uranium nitride particles uniformly mixed without damaging the structure of the uranium nitride particles, and to ensure 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, vibrational forces in different directions can be applied to the mixing region at a predetermined frequency to further improve the mixing effect and achieve homogenization of molybdenum-niobium alloy powder and uranium nitride particles.

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

[0051] S51: Place the mixture obtained in step S40 in the sintering zone.

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

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

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

[0055] In some embodiments, in step S53, the temperature of the sintering region is controlled between 1600-1800°C, the pressure applied to the sintering region 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 molybdenum-niobium alloy powder and uranium nitride particles, reduce the porosity of uranium nitride particles, form a uniform and dense core structure, and at the same time avoid compositional segregation and material oxidation caused by high temperature, thereby improving the quality of the obtained core structure.

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

[0057] Specifically, in step S60, the pellets obtained in step S50 are hot-extruded at a temperature range of 1800-2000℃, a high pressure of 100-200MPa, and a holding pressure of 30-90min to eliminate internal pores in the pellets and promote grain recombination. This improves the density, mechanical properties, and uniformity of the generated uranium nitride particle fuel, further ensuring that high-quality uranium nitride particle fuel is finally obtained.

[0058] An embodiment of this application also provides a uranium nitride particulate fuel, which is prepared using the preparation method of any embodiment of the first aspect of this 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 were used as raw materials. ZrCl4 precursor was added to the raw material molybdenum and niobium metal powders and placed in the reaction zone. Hydrogen gas was introduced into the reaction zone at a rate of 20-50 ml / min. The reaction zone was heated to a temperature range of 800-1200℃, and the raw material molybdenum and niobium metal powders reacted with ZrCl4 and hydrogen gas for 0.5-2 h to obtain molybdenum-niobium alloy powders coated with zirconium. To prepare a uranyl nitrate solution, urea (CO(NH2)2) was used as an organic composite agent to achieve a uranium concentration of 0.1-0.5 mol / L in the solution, and the pH value of the solution was adjusted to 2.0-3.0. The uranyl nitrate solution was stirred at 500-1000 rpm for 1-2 hours within a temperature range of 20-30℃ to convert it into a sol. Ammonia was added to the sol to raise its pH value to 8.0-10.0, causing the sol to coagulate. The sol was then heated in a water bath within a temperature range of 50-80℃ to accelerate the aggregation and sedimentation of the colloid. The sol was then subjected to vibration treatment, with the vibration frequency controlled at 50-100 Hz and the amplitude controlled at 1-2 mm, to obtain uranium oxide particles with a particle diameter of 50-500 μm and a uniform particle size distribution. A nitrogen-hydrogen mixture is introduced into the reaction zone to create a nitrogen-hydrogen atmosphere, with a H2:NH3 volume ratio 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℃, allowing 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 speed of 10-20 m / s to obtain a homogeneous mixture. The mixture is placed in a sintering zone; an inert gas is introduced into the sintering zone; the temperature of the sintering zone is controlled between 1600-1800℃, the pressure applied to the sintering zone is controlled between 50-100MPa, and the discharge energy is controlled between 500-1000A, so that the molybdenum-niobium alloy powder and uranium nitride particles are combined to obtain a pellet with a dense structure. The pellet is hot-extruded at a temperature range of 1800-2000℃, a high pressure of 100-200MPa, and a holding pressure of 30-90min to obtain uranium nitride particle fuel.

[0061] Regarding the embodiments of this application, it should also be noted that, without conflict, the embodiments of this application and the features in the embodiments can be combined with each other to obtain new embodiments.

[0062] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. The scope of protection of this application shall be determined by the scope of the claims.

Claims

1. A method for preparing uranium nitride particulate fuel, characterized in that, It includes the following steps: S10: Process the raw material molybdenum and niobium metal powders to coat the obtained molybdenum-niobium alloy powder with a zirconium coating; S20: Prepare uranium oxide particles with uniform particle size; S30: The uranium oxide particles are placed in the reaction zone, and ammonia gas is introduced into the reaction zone to react the uranium oxide particles with the ammonia gas to obtain low-density uranium nitride particles with uniform particle size. S40: Mix the molybdenum-niobium alloy powder obtained in step S10 with the uranium nitride particles obtained in step S30 to make both uniformly distributed in the resulting mixture; S50: Sintering the mixture to combine the molybdenum-niobium alloy powder with the uranium nitride particles, so that the obtained core block forms a dense structure; S60: Shape the pellet to obtain the uranium nitride particulate fuel.

2. The method according to claim 1, characterized in that, Step S10 also includes the following steps: S11: Add ZrCl4 to the raw material molybdenum and niobium metal powder and place it in the reaction zone; S12: Introduce hydrogen gas into the reaction zone at a predetermined rate; S13: Heat the reaction zone to a predetermined temperature to allow the raw material molybdenum and niobium metal powder to react with the ZrCl4 and hydrogen for a predetermined time.

3. The method according to claim 1, characterized in that, Step S20 also includes the following steps: S21: Preparation of uranyl nitrate solution; S22: Stir the uranyl nitrate solution to convert it into a sol; S23: Add an alkaline substance to the sol to cause the sol to coagulate; S24: Vibrate the sol and control the vibration frequency and amplitude to make the obtained uranium oxide particles have a uniform particle size.

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, Step S30 also includes the following steps: S31: Introduce a nitrogen-hydrogen mixture into the reaction region to create a nitrogen-hydrogen atmosphere in the reaction region; S32: Place the uranium oxide particles obtained in step S20 into the reaction region; S33: Ammonia gas is introduced into the reaction zone at a predetermined rate, and the reaction zone is heated 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 zone at a rate of 0.5-1.0 L / min, and the reaction zone is heated to 800-1000 °C, so that the uranium oxide particles react with the ammonia gas for 2-4 hours.

7. The method according to claim 1, characterized in that, Step S40 also includes the following steps: S41: The molybdenum-niobium alloy powder obtained in step S10 and the uranium nitride particles obtained in step S30 are placed in a mixing region according to a predetermined ratio; S42: The mixing region is made to vibrate at a predetermined frequency for a predetermined time, while argon gas is introduced into the mixing region at a predetermined speed.

8. The method according to claim 1, characterized in that, The S50 step also includes the following steps: S51: Place the mixture obtained in step S40 in the sintering zone; S52: Inert gas is introduced into the sintering region; S53: Control 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 region is controlled between 1600-1800°C, the pressure applied to the sintering region is controlled between 50-100MPa, 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.

11. A uranium nitride particulate fuel, characterized in that, The uranium nitride particulate fuel is prepared using the preparation method described in any one of claims 1-10.

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