A method for the production of a pressurized water reactor mox fuel powder

Abstract

The present application relates to a kind of preparation methods of pressurized water reactor MOX fuel powder, comprising the following steps: by mixed actinide salt and urea solid preparation mixed actinide eutectic, mixed actinide eutectic is directly obtained by deamination, denitrogenation / decarbonation, reduction, MOX fuel powder;The mixed actinide salt is hexavalent actinide nitrate and tetravalent actinide oxalate;When the mixed actinide salt is uranyl nitrate hexahydrate solid and thorium oxalate hexahydrate solid, the MOX fuel powder is (U x Th 1‑x )O2;When the mixed actinide salt is uranyl nitrate hexahydrate solid and plutonium oxalate hexahydrate solid, the MOX fuel powder is (U x Pu 1‑x )O2.The method provided by the present application has simple raw materials, can greatly simplify the preparation process of MOX fuel powder composed of UO2 and PuO2 (or ThO2), reduce the use of process reagent, and does not produce any process waste liquid, thereby providing a simple, high production efficiency, waste liquid-free, more economical and green MOX fuel powder preparation method.

Description

Technical Field

[0001] This invention belongs to the field of nuclear fuel preparation technology, specifically relating to a method for preparing MOX fuel powder for pressurized water reactors. Background Technology

[0002] MOX fuel is one of the most studied nuclear fuel types both domestically and internationally in recent years, and it is a key component in achieving a closed nuclear fuel cycle and sustainable nuclear energy development. In the MOX fuel preparation process, powder preparation is crucial. The quality of the powder, including its composition and homogeneity (impurities, isotopes) and its properties (particle size, specific surface area, bulk density, etc.), directly affects the performance of subsequent fuel pellets. Therefore, MOX powder manufacturing has always been a focus of MOX fuel manufacturing research both at home and abroad.

[0003] To obtain uniformly mixed MOX fuel powder, extensive research has been conducted both domestically and internationally, resulting in the development of multiple process flows. Based on the different powder mixing methods, these processes are mainly divided into two categories: mechanical mixing (commonly known as the dry method) and chemical co-precipitation (commonly known as the wet method). The wet method can achieve better product uniformity and form a solid solution powder. The wet method includes the uranium tricarbonate plutonium ammonium co-precipitation process developed in Germany.

[0004] (AUPuC), Japan forms (U) through microwave denitration of a 1:1 mixture of plutonium nitrate and uranyl nitrate. 0.5 Pu 0.5 PuO2 solid solution powder. The dry process was initially used for the production of fast reactor MOX fuel with high PuO2 content. France and Belgium developed a modified two-step mixing method, the Micronized Main Mixing (MIMAS) process, which replaced the original French one-step mixing (COCA) process and can be used for the production of LWR (light water reactor) MOX fuel with lower PuO2 content. The binderless batching (SBR) process developed in the UK has better Pu distribution uniformity than the MIMAS process. Russia uses the ABC-150 high-efficiency magnetic mixer to prepare uniform MOX powder. The aforementioned wet processes are lengthy, produce a lot of waste liquid, and are difficult to adapt to the requirements of products with different abundances and contents; the dry grinding process is difficult to operate, has high requirements for equipment and process parameters, and inevitably has the problem of plutonium-rich particles. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing MOX fuel powder for pressurized water reactors. This method utilizes a eutectic mixture formed from uranyl nitrate hexahydrate, plutonium oxalate hexahydrate (or thorium oxalate hexahydrate), and urea to prepare a microscopically (molecular level) uniformly mixed powder containing (U... x Pu 1-x O2 or (U x Th 1-xMOX fuel powder containing O2 can be used to produce MOX-type fuel that is irradiated in LWR, FNR and other reactor types.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is: a method for preparing pressurized water reactor MOX fuel powder, the method comprising the following steps:

[0007] S1. Preparation of mixed actinide eutectic: Dry mixed actinide salts are mixed with solid urea in a certain proportion until the mixture becomes a completely clear liquid to obtain mixed actinide eutectic; the mixed actinide salts are hexavalent actinide nitrates and tetravalent actinide oxalates;

[0008] S2, Deammoniation: The mixed actinide eutectic is heated to a specified temperature and held for a specified time according to a specified program to obtain deammoniation powder, wherein the deammoniation powder is a uniformly mixed hexavalent actinide nitrate and tetravalent actinide oxalate;

[0009] S3, Denitrification / Decarbonization: The denitrification powder is heated to a set temperature according to a set program and held at that temperature for a set time to obtain denitrification / decarbonization powder;

[0010] S4. Reduction: The denitrified / decarbonized powder is heated to a certain temperature in an argon atmosphere according to a certain program, and then switched to a hydrogen-argon mixture or a hydrogen atmosphere and kept at that temperature for a certain time to obtain MOX fuel powder.

[0011] Furthermore, the hexavalent actinide nitrate is uranyl nitrate hexahydrate solid, and the tetravalent actinide oxalate is thorium oxalate hexahydrate solid or plutonium oxalate hexahydrate solid.

[0012] Furthermore, the molar ratio of the metal ions in the mixed actinide salt to the urea is 1:9.

[0013] Furthermore, the molar ratio of uranyl nitrate hexahydrate solid to thorium oxalate hexahydrate solid in the mixed actinide salt is ≥95:5, or the molar ratio of uranyl nitrate hexahydrate solid to plutonium oxalate hexahydrate solid in the mixed actinide salt is ≥95:5.

[0014] Furthermore, in the process of mixing the mixed actinide salt and urea solid in step S1, the mixed actinide salt and urea are mixed evenly by one or more of the following methods: shaking the mixture, stirring the mixture, and grinding the mixture.

[0015] Furthermore, in step S1, the mixing process of the mixed actinide salt and urea solid further includes using ultrasonic vibration to mix the mixed actinide salt and urea evenly to obtain a completely clear mixed actinide eutectic.

[0016] Further, step S2 includes the following specific steps: the mixed actinide eutectic is drawn into a crucible using a pipette, and the crucible is heated to 150-160°C according to a specified program and held at that temperature for more than 30 minutes to obtain the deammoniation powder.

[0017] Furthermore, in step S2, the deammoniation process is carried out under an air or argon atmosphere;

[0018] The specified procedure refers to the specified heating rate, which is 5 to 10 °C / min.

[0019] Furthermore, when the mixed actinide salt is uranyl nitrate hexahydrate solid and thorium oxalate hexahydrate solid, the denitrification / decarbonization powder is U3O8 and ThO2 powder;

[0020] When the mixed actinide salt is uranyl nitrate hexahydrate solid and plutonium oxalate hexahydrate solid, the denitrification / decarbonization powder is U3O8 and PuO2 powder.

[0021] Further, in step S3, the deammoniation powder is heated to 650-800°C according to a set program and held at that temperature for more than 30 minutes to obtain denitrification / decarbonization powder.

[0022] Furthermore, in step S3, the denitrification / decarbonization process is carried out in an air or argon atmosphere;

[0023] The "according to the set program" refers to the "according to the set heating rate", which is 5-10℃ / min.

[0024] Further, in step S4, the denitrified / decarbonized powder is heated to 680-900°C at a heating rate of 5-10°C / min under an argon atmosphere, and then switched to a hydrogen-argon mixture or a hydrogen atmosphere and held at that temperature for 10-30 min to obtain MOX fuel powder.

[0025] Furthermore, when the mixed actinide salt is uranyl nitrate hexahydrate solid and thorium oxalate hexahydrate solid, the MOX fuel powder is (U x Th 1-x O2; when the mixed actinide salt is uranyl nitrate hexahydrate solid and plutonium oxalate hexahydrate solid, the MOX fuel powder is (U x Pu 1-x O2;

[0026] Where 0.95 ≤ X < 1.0.

[0027] The beneficial effects of this invention are as follows: The method for preparing MOX fuel powder for pressurized water reactors provided by this invention involves the following steps: preparing a mixed actinide eutectic from mixed actinide salts and solid urea; subjecting the mixed actinide eutectic to ammonia removal, denitrification / decarbonization, and reduction to directly obtain MOX fuel powder; wherein the mixed actinide salts are hexavalent actinide nitrates and tetravalent actinide oxalates; when the mixed actinide salts are uranyl nitrate hexahydrate solid and thorium oxalate hexahydrate solid, the MOX fuel powder is (U... x Th 1-x O2; when the mixed actinide salt is uranyl nitrate hexahydrate solid and plutonium oxalate hexahydrate solid, the MOX fuel powder is (U x Pu 1-x The method provided by this invention directly uses uranyl nitrate solid and plutonium oxalate / thorium oxalate as raw materials. The simplicity of the raw materials greatly simplifies the preparation process of MOX fuel powder composed of UO2 and PuO2 (or ThO2), reduces the use of process reagents, and generates no process waste liquid. Therefore, it provides a simple, efficient, waste-free, more economical, and environmentally friendly method for preparing MOX fuel powder. The specific beneficial effects of this invention are mainly reflected in:

[0028] (1) A mixed actinide eutectic, which is liquid at room temperature, is obtained by directly mixing three solids—uranyl nitrate hexahydrate, plutonium oxalate hexahydrate (or thorium oxalate hexahydrate)—with urea in a certain proportion. This mixture serves as the mother liquor for preparing MOX fuel powder. Compared to the wet process, which involves dissolving the two actinides separately and then co-precipitating them under certain conditions, this method is simpler, has fewer steps, is more efficient, and produces no waste liquid. MOX fuel powder can be obtained by decomposing the mixed actinide eutectic at a certain temperature. Only a high-temperature sintering atmosphere furnace is needed, which is a common piece of equipment already used in conventional UO2 fuel production. No additional specialized equipment is required. Compared to the dry process, this method is simpler to operate and does not require additional equipment. This method greatly simplifies the process flow, effectively reduces production costs, and offers better economic efficiency and safety.

[0029] (2) The mixed actinide eutectic prepared by the present invention has very stable properties, requires only one additive urea, which is easy to obtain, low in cost, and can be completely removed when heated to around 160°C.

[0030] (3) The MOX fuel powder prepared by this invention has good chemical composition uniformity and is uniformly mixed at the microscopic molecular level.

[0031] (4) The MOX fuel powder preparation method provided by this invention can prepare MOX powder particles of various sizes and shapes as needed. For example, by combining it with vibration dispersion, microfluidic method, two-phase dispersion method or aerosol spraying, monodisperse MOX microspheres with a controllable particle size range of 1μm to 1mm and a narrow particle size distribution range can be prepared. These microspheres can be applied to TRISO fuel and other uses, and can serve as a novel, economical, and green MOX microsphere preparation scheme. Moreover, this MOX fuel powder preparation scheme can also be extended to all hexavalent actinide nitrate and tetravalent actinide oxalate systems. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the process for preparing MOX fuel powder for pressurized water reactors according to an embodiment of the present invention;

[0033] Figure 2 This is a comparison diagram of the process flow for preparing MOX fuel powder by the method provided in this embodiment of the invention and by dry and wet methods;

[0034] Figure 3 This is a scanning electron microscope-energy dispersive spectroscopy (SEM-EDS) image showing the elemental surface distribution of the MOX fuel powder prepared in Example 1 of this invention. Detailed Implementation

[0035] The technical solutions in the embodiments of the present invention will be further described clearly and completely below with reference to the accompanying drawings and examples. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0036] Deep eutectic solvents (DES) are generally composed of two or three components, often obtained by mixing metal salts with hydrogen bond donors. The components are interconnected by forming hydrogen bonds and have low lattice energy, resulting in a melting point lower than that of any single component. Macroscopically, most DES are liquids at room temperature. In their 2019 article "Structure and properties of 'Type IV' lanthanide nitrate hydrate: urea deep eutectic solvents" published in ACS's Sustainable Chemistry & Engineering, Hammond et al. studied the properties and structure of DES formed by mixing trivalent lanthanide metals such as cerium, protactinium, and neodymium with urea, confirming the hydrogen bonding between water and urea. In their 2021 article "Electrochemical and thermodynamic insights on actinide type (IV) deep eutectic solvent" published in the Journal of Molecular Liquids, Ruma Gupta et al. discovered that when uranyl nitrate hexahydrate (UNH) and urea are mixed in a certain proportion, a eutectic can also be formed. By adjusting the ratio of uranyl nitrate hexahydrate to urea (molar ratio of 1:4), its melting point can be reduced to below 0°C. Furthermore, UO2 nanocrystals were prepared by electrochemically reducing this eutectic.

[0037] In their previous research, the inventors discovered that a 1:9 molar ratio of uranyl nitrate hexahydrate to urea could also form a eutectic, which remained stable at room temperature for several months, exhibiting superior stability compared to a 1:4 uranium-containing eutectic. Using this 1:9 uranium-containing eutectic, combined with microfluidic methods or vibrational dispersion, UO2 fuel core microspheres with tristructural isotropic (TRISO) coatings for high-temperature gas-cooled reactor fuel can be prepared.

[0038] In this invention, the inventors discovered that a eutectic can also be formed when the molar ratio of mixed actinide salts (uranyl nitrate hexahydrate + thorium oxalate hexahydrate / plutonium oxalate hexahydrate) to urea is 1:9. Based on this, a method for preparing pressurized water reactor MOX fuel powder is provided to address the shortcomings of mixed oxide fuel (MOX) powder preparation processes, namely, the long wet process flow and large amount of waste liquid; and the difficult operation and high requirements for equipment and process parameters in the dry grinding process. The technical concept is as follows: after adding a small amount of flux to uranyl nitrate powder and thorium oxalate (or plutonium oxalate) powder, a homogeneous liquid-eutectic (DES) is obtained. After heating, the flux is removed and the oxalate and nitrate are decomposed to obtain a mixed oxide powder containing U3O8 and PuO2 (or ThO2). It can be further reduced to obtain a uniformly mixed elemental composition containing U3O8 at the microscopic (molecular level). x Pu 1-x O2 or (U x Th 1-x MOX fuel powder prepared using O2. This method is an advanced anhydrous process that is simple, easy to operate, reduces the use of process reagents, generates no waste liquid, simplifies the operation process, requires no additional equipment, reduces production costs, and improves production efficiency. A comparison of the process flow of the method provided in this embodiment with dry and wet methods for preparing MOX fuel powder is shown in the figure below. Figure 2 As shown.

[0039] like Figures 1-2 As shown in this embodiment, a method for preparing pressurized water reactor MOX fuel powder is provided, the method comprising the following steps:

[0040] S1. Preparation of mixed actinide eutectic: Dry mixed actinide salts and solid urea are mixed in a certain proportion until the mixture becomes a completely clear liquid to obtain mixed actinide eutectic.

[0041] Optionally, the mixed actinide salts include hexavalent actinide nitrates and tetravalent actinide oxalates.

[0042] Specifically, the hexavalent actinide nitrate is uranyl nitrate hexahydrate (UNH) solid, and the tetravalent actinide oxalate is thorium oxalate hexahydrate solid or plutonium oxalate hexahydrate solid; that is, the mixed actinide salt is uranyl nitrate hexahydrate solid and thorium oxalate hexahydrate solid, or the mixed actinide salt is uranyl nitrate hexahydrate solid and plutonium oxalate hexahydrate solid.

[0043] Specifically, the molar ratio of the metal ions in the mixed actinide salt to the urea is 1:9.

[0044] In one specific embodiment, the molar ratio of uranyl nitrate hexahydrate solid to thorium oxalate hexahydrate solid in the mixed actinide salt is ≥95:5, or the molar ratio of uranyl nitrate hexahydrate solid to plutonium oxalate hexahydrate solid in the mixed actinide salt is ≥95:5.

[0045] Optionally, during the mixing of the mixed actinide salt and urea in step S1, the mixed actinide salt and urea are mixed evenly by shaking and / or stirring the mixture.

[0046] In one specific embodiment, in step S1, the mixed actinide salt and urea are mixed evenly by shaking and ultrasonic vibration, causing the solid powder to soften and gradually liquefy, thereby obtaining a completely clear mixed actinide eutectic.

[0047] In another specific embodiment, when the sample amount of the mixed actinide eutectic to be prepared is large, it can be mixed by grinding and stirring in a mortar to mix the mixed actinide salt and urea evenly.

[0048] Optionally, in step S1, the mixture formed by the mixed actinide salt and urea is heated to make the mixed actinide salt and urea mix evenly, so as to obtain a completely clear mixed actinide eutectic.

[0049] S2, Deammoniation: The mixed actinide eutectic is heated to a specified temperature and held for a specified time according to a specified procedure to obtain deammoniation powder;

[0050] Specifically, in step S2, the mixed actinide eutectic is pipetted into a crucible, and the crucible is heated to 150-160°C and held for more than 30 minutes according to a specified program to remove urea from the mixed actinide eutectic. The resulting deaminated powder is a uniformly mixed hexavalent actinide nitrate and tetravalent actinide oxalate.

[0051] Optionally, in step S2, the deammoniation process is carried out in an air or argon atmosphere, and the specified procedure refers to the specified heating rate, which is 5 to 10 °C / min.

[0052] S3, Denitrification / Decarbonization: The denitrification powder is heated to a set temperature according to a set program and held at that temperature for a set time to obtain denitrification / decarbonization powder;

[0053] Specifically, when the mixed actinide salt is uranyl nitrate hexahydrate solid and thorium oxalate hexahydrate solid, the denitrification / decarbonization powder is U3O8 and ThO2 powder; when the mixed actinide salt is uranyl nitrate hexahydrate solid and plutonium oxalate hexahydrate solid, the denitrification / decarbonization powder is U3O8 and PuO2 powder.

[0054] Specifically, in step S3, the denitrification / decarbonization process is carried out in an air or argon atmosphere. The deammoniation powder is heated to 650-800°C according to a set program and held at that temperature for more than 30 minutes. The hexavalent actinide nitrate and tetravalent actinide oxalate mixed evenly in the deammoniation powder undergo thermal decomposition, and the resulting denitrification / decarbonization powder is the corresponding actinide metal oxide U3O8 and ThO2 powder, or U3O8 and PuO2 powder.

[0055] Optionally, in step S3, "according to the set program" means according to the set heating rate, which is 5 to 10 °C / min.

[0056] S4. Reduction: The denitrified / decarbonized powder is heated to a certain temperature in an argon atmosphere according to a certain program, and then switched to a hydrogen-argon mixture or a hydrogen atmosphere and kept at that temperature for a certain time to obtain MOX fuel powder.

[0057] Specifically, in step S4, the denitrified / decarbonized powder is heated to 680-900°C at a heating rate of 5-10°C / min under an argon atmosphere, and then switched to a hydrogen-argon mixture or a hydrogen atmosphere and held at that temperature for 10-30 minutes to obtain MOX fuel powder.

[0058] Specifically, when the mixed actinide salt is uranyl nitrate hexahydrate solid and thorium oxalate hexahydrate solid, the MOX fuel powder is (U x Th 1-x O2; when the mixed actinide salt is uranyl nitrate hexahydrate solid and plutonium oxalate hexahydrate solid, the MOX fuel powder is (U x Pu 1-x O2; where 0.95≤X<1.0.

[0059] The following examples further illustrate specific embodiments of the present invention.

[0060] Example 1: Eutectic process (U x Th 1-x Example of preparation of O2 type (i.e., a mixture of UO2 and ThO2, where X = 0.95) MOX fuel powder

[0061] S11. Preparation of mixed actinide eutectic: First, take 0.0256 g (0.05 mmol) of dry thorium oxalate hexahydrate solid, 0.477 g (0.95 mmol) of uranyl nitrate hexahydrate solid and 0.5405 g (9 mmol) of urea solid in a transparent glass bottle. Gently shake the glass bottle and use ultrasonic vibration to mix the sample thoroughly. During the mixing process, the solid powder softens and gradually liquefies. After about 5 to 10 minutes, the mixture becomes a completely clear liquid, thus obtaining a U(VI) / Th(IV) type mixed actinide eutectic with a Th(IV) content of 5 At% (atomic percentage).

[0062] Optionally, when the sample quantity of the mixed actinide eutectic to be prepared is large, it can be mixed by grinding and stirring in a mortar.

[0063] S12, Deamination: Using a pipette, 20 μL of 5 At% U / Th type mixed actinide eutectic is placed in a crucible. The liquid is heated to 150-160°C at a heating rate of 5-10°C / min under an air / argon atmosphere and held for 30 min to remove urea. The resulting deamination powder is a uniformly mixed hexavalent actinide nitrate and tetravalent actinide oxalate.

[0064] S13, Denitrification / Decarbonization: The above denitrification powder is heated to 650-800℃ at a heating rate of 5-10℃ / min under an air / argon atmosphere and held for more than 30min to fully decompose the hexavalent actinide nitrate and tetravalent actinide oxalate mixed evenly in the denitrification powder. The resulting denitrification / decarbonization powder is U3O8 and ThO2 powder.

[0065] S14. Reduction: The U3O8 and ThO2 powders are heated to 680-900°C under an argon atmosphere at a heating rate of 5-10°C / min, and then reduced for 10-15 min under a 4% hydrogen-argon (V / V) mixed atmosphere (or pure hydrogen). The resulting MOX fuel powder is a uniformly mixed UO2 and ThO2 powder.

[0066] The elemental surface distribution analysis results of the MOX fuel powder obtained in Example 1 are shown in the figure below. Figure 3 As shown. Figure 3 The analysis results show that UO2 and ThO2 powders are uniformly distributed in the MOX fuel powder prepared in Example 1, which indicates that the MOX fuel powder obtained in Example 1 has good chemical composition uniformity and is uniformly mixed at the microscopic molecular level.

[0067] The MOX fuel powder preparation method provided in this embodiment can prepare MOX powder particles of various sizes and shapes as needed. For example, by combining methods such as vibration dispersion, microfluidic dispersion, two-phase dispersion, or aerosol spraying, monodisperse MOX microspheres with a controllable particle size range of 1 μm to 1 mm and a narrow particle size distribution can be prepared. These microspheres can be used in TRISO fuel and other applications, serving as a novel, economical, and green MOX microsphere preparation method. This MOX fuel powder preparation method can also be extended to all hexavalent actinide nitrate and tetravalent actinide oxalate systems.

[0068] The methods described in this invention are not limited to the specific embodiments described above. The embodiments are merely illustrative examples of this invention, and this invention can also be implemented in other specific ways or forms without departing from the spirit or essential characteristics of this invention. Therefore, the described embodiments should be considered illustrative rather than limiting in any respect. The scope of this invention should be defined by the appended claims, and any variations equivalent to the intent and scope of the claims should also be included within the scope of this invention.

Claims

1. A method for preparing pressurized water reactor MOX fuel powder, characterized in that, The method includes the following steps: S1. Preparation of mixed actinide eutectic: Dry mixed actinide salts are mixed with solid urea in a certain proportion until the mixture becomes a completely clear liquid to obtain mixed actinide eutectic; the mixed actinide salts are hexavalent actinide nitrates and tetravalent actinide oxalates; S2, Deammoniation: The mixed actinide eutectic is heated to a specified temperature and held for a specified time according to a specified program to obtain deammoniation powder, wherein the deammoniation powder is a uniformly mixed hexavalent actinide nitrate and tetravalent actinide oxalate; S3, Denitrification / Decarbonization: The denitrification powder is heated to a set temperature according to a set program and held at that temperature for a set time to obtain denitrification / decarbonization powder; S4. Reduction: The denitrified / decarbonized powder is heated to a certain temperature in an argon atmosphere according to a certain program, and then switched to a hydrogen-argon mixture or a hydrogen atmosphere and kept at that temperature for a certain time to obtain MOX fuel powder.

2. The method for preparing pressurized water reactor MOX fuel powder according to claim 1, characterized in that, The hexavalent actinide nitrate is uranyl nitrate hexahydrate solid, and the tetravalent actinide oxalate is thorium oxalate hexahydrate solid or plutonium oxalate hexahydrate solid.

3. The method for preparing pressurized water reactor MOX fuel powder according to claim 2, characterized in that, The molar ratio of the metal ions in the mixed actinide salt to the urea is 1:

9.

4. The method for preparing pressurized water reactor MOX fuel powder according to claim 2, characterized in that, The molar ratio of uranyl nitrate hexahydrate solid to thorium oxalate hexahydrate solid in the mixed actinide salt is ≥95:5, or the molar ratio of uranyl nitrate hexahydrate solid to plutonium oxalate hexahydrate solid in the mixed actinide salt is ≥95:

5.

5. The method for preparing pressurized water reactor MOX fuel powder according to claim 1, characterized in that, In step S1, during the mixing of the mixed actinide salt and urea solid, the mixed actinide salt and urea are mixed evenly by one or more of the following methods: shaking the mixture, stirring the mixture, and grinding the mixture.

6. The method for preparing pressurized water reactor MOX fuel powder according to claim 5, characterized in that, In step S1, the mixing process of the mixed actinide salt and urea solid further includes using ultrasonic vibration to mix the mixed actinide salt and urea evenly to obtain a completely clear mixed actinide eutectic.

7. The method for preparing pressurized water reactor MOX fuel powder according to claim 1, characterized in that, Step S2 includes the following specific steps: the mixed actinide eutectic is drawn into a crucible using a pipette, and the crucible is heated to 150-160°C according to a specified program and held at that temperature for more than 30 minutes to obtain the deammoniation powder.

8. The method for preparing pressurized water reactor MOX fuel powder according to claim 1, characterized in that, In step S2, the deammoniation process is carried out under an air or argon atmosphere; The specified procedure refers to the specified heating rate, which is 5 to 10 °C / min.

9. The method for preparing pressurized water reactor MOX fuel powder according to claim 2, characterized in that, When the mixed actinide salt is uranyl nitrate hexahydrate solid and thorium oxalate hexahydrate solid, the denitrification / decarbonization powder is U3O8 and ThO2 powder; when the mixed actinide salt is uranyl nitrate hexahydrate solid and plutonium oxalate hexahydrate solid, the denitrification / decarbonization powder is U3O8 and PuO2 powder.

10. The method for preparing pressurized water reactor MOX fuel powder according to claim 1, characterized in that, In step S3, the deammoniation powder is heated to 650-800°C according to a set program and held at that temperature for more than 30 minutes to obtain denitrification / decarbonization powder.

11. The method for preparing pressurized water reactor MOX fuel powder according to claim 1, characterized in that, In step S3, the denitrification / decarbonization process is carried out in an air or argon atmosphere; The "according to the set program" refers to the "according to the set heating rate", which is 5-10℃ / min.

12. The method for preparing pressurized water reactor MOX fuel powder according to claim 1, characterized in that, In step S4, the denitrified / decarbonized powder is heated to 680-900°C at a heating rate of 5-10°C / min under an argon atmosphere, and then switched to a hydrogen-argon mixture or a hydrogen atmosphere and held at that temperature for 10-30 minutes to obtain MOX fuel powder.

13. The method for preparing pressurized water reactor MOX fuel powder according to claim 2, characterized in that, When the mixed actinide salt is uranyl nitrate hexahydrate solid and thorium oxalate hexahydrate solid, the MOX fuel powder is (U x Th 1-x O2; when the mixed actinide salt is uranyl nitrate hexahydrate solid and plutonium oxalate hexahydrate solid, the MOX fuel powder is (U x Pu 1-x O2; Where 0.95 ≤ X < 1.0.

Images