Preparation method of AnO2 type MOX fuel powder

Abstract

The invention relates to a preparation method of AnO2 type MOX fuel powder, which comprises the following steps: preparing a mixed actinide eutectic melt from a mixed actinide salt and a urea solid, and carrying out deamination and denitrification / decarbonization on the mixed actinide eutectic melt to directly obtain the AnO2 type MOX fuel powder, the mixed actinide salt consists of tetravalent actinide nitrate and tetravalent actinide oxalate; when the tetravalent actinide nitrate is a plutonium nitrate pentahydrate solid, a thorium nitrate hexahydrate solid or a U (NO3) 4.3-4H2O solid, and the tetravalent actinide oxalate is a thorium oxalate hexahydrate solid, a plutonium oxalate hexahydrate solid or an oxalic acid U (IV) solid, the AnO2 type MOX fuel powder is (ThxPu1-x) O2, (UxTh1-x) O2 or (UxPu1-x) O2 powder. According to the preparation method, plutonium nitrate / thorium nitrate / U (NO3) 4. 3-4H2O and thorium oxalate / plutonium oxalate / oxalic acid U (IV) are directly adopted as raw materials, the preparation process flow of the AnO2 type MOX fuel powder can be simplified, the use of process reagents is reduced, and no process waste liquid is generated, so that the preparation method of the MOX fuel powder, which is simple, convenient, high in production efficiency, free of waste liquid and more economical and green, is provided.

Description

Technical Field

[0001] The present invention belongs to the technical field of nuclear fuel preparation, and particularly relates to an AnO 2 Preparation method of MOX fuel powder. Background Art

[0002] MOX fuel is one of the most popular nuclear fuel types in recent years. It is one of the key links to achieve closed nuclear fuel cycle and sustainable development of nuclear energy. In the MOX fuel preparation process, powder preparation is a key link. The quality of the powder, including composition and uniformity (impurities, isotopes), and the performance of the powder (particle size, specific surface area, bulk density, etc.) directly affects the performance of the subsequent pellets. Therefore, MOX powder manufacturing has always been the focus of MOX fuel manufacturing research at home and abroad.

[0003] In order to obtain uniformly mixed MOX fuel powder, a lot of research has been carried out at home and abroad, and multiple process flows have been developed. According to the different powder mixing methods, they are mainly divided into two categories: mechanical mixing method (commonly known as dry method) and chemical co-precipitation method (commonly known as wet method). The wet method can obtain better product uniformity and form solid solution powder. The wet method includes the German uranium tricarbonate plutonium ammonium co-precipitation process

[0004] (AUPuC), Japan formed by microwave denitrification of a 1:1 mixed solution of plutonium nitrate and uranyl nitrate (U 0.5 Pu 0.5 ) 2 The dry method was first used for PuO 2 For the production of fast reactor MOX fuel with high PuO content, the two-step mixing method developed by France and Belgium, namely the micronized main mixing (MIMAS) process, replaced the original French one-step mixing (COCA) process and can be used for PuO 2 Production of low-content LWR (light water reactor) MOX fuel. The binderless process (SBR) developed by the UK has better Pu distribution uniformity than the MIMAS process. Russia relies on the ABC-150 high-efficiency magnetic mixer to prepare uniform MOX powder. The above-mentioned wet process has a long process flow and a lot of waste liquid, and it is difficult to adapt to the requirements of products with different abundances and contents; the dry grinding process is difficult to operate, has high requirements on equipment and process parameters, and inevitably has the problem of plutonium-rich particles. Summary of the invention

[0005] The object of the present invention is to provide an AnO 2 A method for preparing MOX fuel powder using plutonium nitrate pentahydrate (or thorium nitrate hexahydrate, or U(NO 3 ) 4 3-4 hours 2O solid), thorium oxalate hexahydrate (or plutonium oxalate hexahydrate, or U(IV) oxalate) and urea to form a low melt, and prepare a microscopic (molecular level) mixed (Th x Pu 1-x ) 2 、(U x Th 1-x ) 2 or x Pu 1-x ) 2 Type MOX fuel powder.

[0006] In order to achieve the above purpose, the technical solution adopted by the present invention is: an AnO 2 A method for preparing MOX fuel powder, the method comprising the following steps:

[0007] S1. preparing a mixed actinide eutectic: mixing a dry mixed actinide salt with urea solid in a certain proportion until the mixture becomes a completely clear liquid, thereby obtaining a mixed actinide eutectic; the mixed actinide salt comprises tetravalent actinide nitrate and tetravalent actinide oxalate;

[0008] S2, deamination: the mixed actinide eutectic is heated to a specified temperature according to a specified procedure and kept at the temperature for a specified time to obtain a deamination powder, wherein the deamination powder comprises a mixed actinide salt and an actinide oxide;

[0009] S3, denitrification / decarbonization: The deamination powder is heated to a set temperature and kept warm for a set time according to a set program, and the denitrification / decarbonization powder obtained is AnO 2 Type MOX fuel powder.

[0010] Furthermore, the tetravalent actinide nitrate is solid plutonium nitrate pentahydrate, solid thorium nitrate hexahydrate or U(NO 3 ) 4 3-4 hours 2 O solid, the tetravalent actinide oxalate is thorium oxalate hexahydrate solid, plutonium oxalate hexahydrate solid or U(IV) oxalate solid.

[0011] Furthermore, the molar ratio of the metal ions in the mixed actinide salt to the urea is 1:9.

[0012] Furthermore, in the process of mixing the mixed actinide salt and the urea solid in step S1, the mixture is mixed by stirring and / or grinding the mixture.

[0013] Furthermore, in the mixing process of the mixed actinide salt and the urea solid in step S1, the mixed actinide salt and the urea mixture are heated to obtain a completely clarified mixed actinide eutectic;

[0014] When insoluble matter still exists in the mixture formed by the mixed actinide salt and urea after heating, deionized water is added to the mixture and ultrasonic treatment is performed to obtain a completely clarified mixed actinide eutectic.

[0015] Further, step S2 includes the following specific steps: sucking the mixed actinide eutectic into a crucible by a pipette, and heating the crucible to 150-160° C. according to a specified program and keeping the temperature for more than 30 minutes to obtain the deaminated powder.

[0016] Further, in step S2, the deamination process is carried out under air or argon atmosphere;

[0017] The specified procedure refers to a specified heating rate, and the specified heating rate is 5-10°C / min.

[0018] Further, in step S3, the deaminated powder is heated to 500-800°C according to a set program and kept at this temperature for more than 30 minutes to obtain AnO 2 Type MOX fuel powder.

[0019] Further, in step S3, the denitrification / decarburization process is carried out under air or argon atmosphere;

[0020] The setting procedure refers to the setting heating rate, and the setting heating rate is 5-10°C / min.

[0021] Furthermore, when the mixed actinide salt is a solid plutonium nitrate pentahydrate and a solid thorium oxalate hexahydrate, or the mixed actinide salt is a solid thorium nitrate hexahydrate and a solid plutonium oxalate hexahydrate, the AnO 2 Type MOX fuel powder is (Th x Pu 1-x ) 2 powder;

[0022] When the mixed actinide salt is a solid plutonium nitrate pentahydrate and a solid thorium oxalate hexahydrate, 0.0<X≤0.1; when the mixed actinide salt is a solid thorium nitrate hexahydrate and a solid plutonium oxalate hexahydrate, 0.9≤X<1.0.

[0023] Further, when the mixed actinide salt is U(NO 3 ) 4 3-4 hours 2 When the AnO is a solid and a thorium oxalate hexahydrate is a solid, or the mixed actinide salt is a thorium nitrate hexahydrate is a solid and a U(IV) oxalate is a solid, 2 Type MOX fuel powder is (U x Th 1-x ) 2 powder;

[0024] When the mixed actinide salt is U(NO 3 ) 4 3-4 hours 2 When the mixed actinide salt is a solid thorium nitrate hexahydrate and a solid thorium oxalate hexahydrate, 0.9≤X<1.0; when the mixed actinide salt is a solid thorium nitrate hexahydrate and a solid U(IV) oxalate, 0.0<X≤0.1.

[0025] Further, when the mixed actinide salt is U(NO 3 ) 4 3-4 hours 2 When the AnO is a solid and a solid plutonium oxalate hexahydrate, or the mixed actinide salt is a solid plutonium nitrate pentahydrate and a solid U(IV) oxalate, the AnO 2 Type MOX fuel powder is (U x Pu 1-x ) 2 powder;

[0026] When the mixed actinide salt is U(NO 3 ) 4 3-4 hours 2 When the mixed actinide salt is a solid plutonium nitrate pentahydrate and a solid U(IV) oxalate, 0.0<X≤0.1.

[0027] The beneficial effect of the present invention is that: using the AnO 2 The method for preparing MOX fuel powder comprises the following steps: preparing a mixed actinide eutectic from a mixed actinide salt and urea solid, and directly obtaining AnO 2 type MOX fuel powder; the mixed actinide salt is composed of tetravalent actinide nitrate and tetravalent actinide oxalate; when the mixed actinide salt is a solid plutonium nitrate pentahydrate and a solid thorium oxalate hexahydrate, or the mixed actinide salt is a solid thorium nitrate hexahydrate and a solid plutonium oxalate hexahydrate, the AnO 2 Type MOX fuel powder is (Th x Pu 1-x ) 2 When the mixed actinide salt is U(NO 3 ) 4 3-4 hours 2 When the AnO is a solid and a thorium oxalate hexahydrate is a solid, or the mixed actinide salt is a thorium nitrate hexahydrate is a solid and a U(IV) oxalate is a solid, 2 Type MOX fuel powder is (U x Th 1-x ) 2 Powder; when the mixed actinide salt is U(NO 3 )4 3-4 hours 2 When the AnO is a solid and a solid plutonium oxalate hexahydrate, or the mixed actinide salt is a solid plutonium nitrate pentahydrate and a solid U(IV) oxalate, the AnO 2 Type MOX fuel powder is (U x Pu 1-x ) 2 powder.

[0028] The method provided by the present invention has simple raw materials, and directly uses plutonium nitrate / thorium nitrate / U(IV) nitrate and plutonium oxalate / thorium oxalate / U(IV) oxalate as raw materials, which can greatly simplify the preparation of AnO 2 ((Th x Pu 1-x ) 2 、(U x Th 1-x ) 2 or x Pu 1-x ) 2 The invention provides a process flow for preparing MOX fuel powder of the type (such as , etc.), reduces the use of process reagents, and does not generate any process waste liquid, thereby providing a simple, efficient, waste-free, more economical and green MOX fuel powder preparation method. The specific beneficial effects of the invention are mainly reflected in:

[0029] (1) A mixed actinide eutectic obtained by directly mixing three solids, namely, plutonium nitrate pentahydrate (or thorium nitrate hexahydrate), thorium oxalate hexahydrate (or plutonium oxalate hexahydrate) and urea in a certain proportion and being liquid at room temperature is used as the mother liquor for preparing MOX fuel powder. Compared with the wet method in which two actinide salts are first dissolved into solutions and then co-precipitated under certain conditions, the process is simple, with fewer steps, high efficiency and no waste liquid is generated; MOX fuel powder can be obtained by decomposing the mixed actinide eutectic at a certain temperature, and only a high-temperature sintering atmosphere furnace is required, without the need to add other special equipment. Compared with the dry method, the operation is simple and no additional equipment is required. This method can greatly simplify the process flow, effectively reduce production costs, and has better economy and safety.

[0030] (2) The mixed actinide eutectic prepared by the present invention has very stable properties and requires only one additive, urea, which is easily available, low in cost, and can be completely removed by heating to around 160°C.

[0031] (3) The MOX fuel powder prepared by the present invention has good uniformity of chemical composition and is evenly mixed at the microscopic molecular level.

[0032] (4) Using AnO provided by the present invention 2The preparation method of MOX fuel powder can prepare AnO 2 Monodisperse AnO with a controllable particle size range of 1 μm to 1 mm and a narrow particle size distribution range can be prepared by using a vibration dispersion method, a microfluidics method, a two-phase dispersion method or an aerosol spray method. 2 The MOX microspheres are applied to TRISO fuel and other purposes, and can be used as a new, economical and green MOX microsphere preparation method. 2 The preparation scheme of MOX fuel powder can also be extended to all tetravalent actinide nitrate and tetravalent actinide oxalate systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is an AnO described in an embodiment of the present invention. 2 Schematic diagram of the process for preparing MOX fuel powder;

[0034] Figure 2 It is a process flow chart comparing the method provided by this embodiment of the present invention with the dry method and the wet method for preparing MOX fuel powder;

[0035] Figure 3 It is AnO prepared in Example 1 of the present invention. 2 Type (U 0.9 Th 0.1 O 2 )Scanning electron microscope-energy dispersive spectrometer element surface distribution analysis results of MOX fuel powder. DETAILED DESCRIPTION

[0036] The technical solutions in the embodiments of the present invention will be further clearly and completely described below in conjunction with the drawings and embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0037] Deep eutectic solvents (DES) are generally composed of two or three components, often a mixture of metal salts and hydrogen bond donors. The components are connected to each other by hydrogen bonds and have a small lattice energy, which results in the melting point of the deep eutectic mixture being lower than the melting point of any component alone. Macroscopically, most deep eutectic mixtures are liquid at room temperature. In the article "Structure and properties of 'Type IV' lanthanide nitrate hydrate: urea eutectic solvents" published by Hammond et al. in Sustainable Chemistry & Engineering of ACS in 2019, the performance and structure of the deep eutectic mixture formed by the mixture of trivalent lanthanide metals such as cerium, protactinium and neodymium with urea were studied, and the hydrogen bonding between water and urea was confirmed. In the article "Electrochemical and thermodynamic insights on actinide type (IV) deep eutectic solvent" published in Journal of Molecular Liquids in 2021, Ruma Gupta et al. found that when uranyl nitrate hexahydrate (UNH) and urea are mixed in a certain proportion, a low eutectic will also be formed. By adjusting the ratio of uranyl nitrate hexahydrate to urea (at a molar ratio of 1:4), the melting point can be reduced to below 0°C, and UO was obtained by electrochemical reduction of the low eutectic. 2 Nanocrystals.

[0038] The inventors found in previous studies that a 1:9 molar ratio of uranyl nitrate hexahydrate to urea can also form a low-melting melt, which is stable for several months at room temperature and is more stable than a 1:4 type uranium-containing low-melting melt. The 1:9 type uranium-containing low-melting melt, combined with microfluidics or vibration dispersion methods, can be used to prepare UO2 tristructural isotropic (TRISO) coated fuel particles for high-temperature gas-cooled reactor fuel. 2 Fuel core microspheres.

[0039] In the embodiment of the present invention, the inventors have found through research that mixed actinide salts (plutonium nitrate pentahydrate, thorium nitrate hexahydrate or U(NO 3 ) 4 3-4 hours 2 O), thorium oxalate hexahydrate (plutonium oxalate hexahydrate or U(IV) oxalate) and urea can also form a low eutectic when the molar ratio is 1:9. Based on this, an AnO 2A new method for preparing MOX fuel powder is provided to solve the shortcomings of the mixed oxide fuel (MOX) fuel powder preparation process, namely, the wet process is long and has a lot of waste liquid; the dry grinding process is difficult to operate and has high requirements for equipment and process parameters. The technical concept is: after adding a small amount of co-solvent to thorium nitrate / plutonium / U(IV) powder and thorium oxalate / plutonium / U(IV) powder, a uniform liquid-low eutectic (DES) is obtained. After heating, the co-solvent is removed and the nitrate and oxalate are decomposed to obtain MOX fuel powder (mixed oxide powder) with a uniformly mixed elemental composition at the microscopic level (molecular level). This method is an advanced anhydrous process with a simple process and easy operation. It can reduce the use of process reagents, does not generate waste liquid, simplifies the operation process, and does not require additional equipment, thereby reducing production costs and improving production efficiency. The process flow comparison between the method provided in this embodiment and the dry and wet methods for preparing MOX fuel powder is shown in the figure below. Figure 2 shown.

[0040] like Figures 1-2 As shown, this embodiment provides an AnO 2 A method for preparing MOX fuel powder, the method comprising the following steps:

[0041] S1. preparing a mixed actinide eutectic: mixing a dry mixed actinide salt with urea solid in a certain proportion until the mixture becomes a completely clear liquid to obtain a mixed actinide eutectic;

[0042] Optionally, the mixed actinide salt consists of tetravalent actinide nitrate and tetravalent actinide oxalate.

[0043] Specifically, the tetravalent actinide nitrate is solid plutonium nitrate pentahydrate, solid thorium nitrate hexahydrate or U(NO 3 ) 4 3-4 hours 2 O solid, the tetravalent actinide oxalate is thorium oxalate hexahydrate solid, plutonium oxalate hexahydrate or U(IV) oxalate) solid.

[0044] Specifically, the molar ratio of the metal ions in the mixed actinide salt to the urea is 1:9.

[0045] In a specific embodiment, in the mixed actinide eutectic, the doping concentration of the tetravalent actinide oxalate is 9.0 At % (atomic percentage).

[0046] Optionally, during the mixing process of the mixed actinide salt and urea in step S1, the mixed actinide salt and urea are mixed uniformly by stirring the mixture.

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

[0048] Optionally, in step S1, the mixture formed by the mixed actinide salt and urea is heated to mix the mixed actinide salt and urea uniformly to obtain a completely clarified mixed actinide eutectic.

[0049] In a specific embodiment, in step S1, the specific method of heating is: heating the mixture formed by the mixed actinide salt and urea on a hot plate, and the heating condition is heating at 80-100° C. for about 5-10 minutes.

[0050] In another specific embodiment, when insoluble matter still exists after heating the mixture formed by the mixed actinide salt and urea, deionized water is added to the mixture and ultrasonic treatment is performed to obtain a completely clarified mixed actinide eutectic.

[0051] S2, deamination: the mixed actinide eutectic is heated to 150-160° C. according to a specified procedure and kept at this temperature for more than 30 minutes to obtain a deamination powder, wherein the deamination powder comprises a mixed actinide salt and an actinide oxide;

[0052] Specifically, in step S2, the mixed actinide eutectic is sucked into a crucible by a pipette, and the crucible is heated to 150-160° C. according to a specified program and kept warm for more than 30 minutes to remove urea in the mixed actinide eutectic. The obtained deaminated powder includes a uniformly mixed mixed actinide salt and actinide oxides formed after thermal decomposition of a portion of tetravalent actinide nitrates in the mixed actinide salt to remove nitrate.

[0053] Optionally, in step S2, the deamination process is carried out in air or argon atmosphere, and the specified procedure refers to a specified heating rate, and the specified heating rate is 5-10°C / min.

[0054] S3, denitrification / decarbonization: The deamination powder is heated to 500-800°C according to the set program and kept warm for more than 30 minutes. The denitrification / decarbonization powder obtained is AnO 2 Type MOX fuel powder;

[0055] Specifically, in step S3, the denitrification / decarbonization process is carried out in air or argon atmosphere, the deaminated powder is heated to 500-800°C according to a set program and kept warm for more than 30 minutes, and the tetravalent actinide nitrate and tetravalent actinide oxalate in the deaminated powder are thermally decomposed to obtain the denitrification / decarbonization powder corresponding to AnO 2 Type MOX fuel powder.

[0056] Optionally, in step S3, following a set program refers to following a set heating rate, and the set heating rate is 5-10° C. / min.

[0057] Optionally, when in the mixed actinide salt, the tetravalent actinide nitrate is a solid plutonium nitrate pentahydrate, the tetravalent actinide oxalate is a solid thorium oxalate hexahydrate, or the tetravalent actinide nitrate is a solid thorium nitrate hexahydrate, the tetravalent actinide oxalate is a solid plutonium oxalate hexahydrate, the An O 2 Type MOX fuel powder is (Th x Pu 1-x ) 2 Type powder.

[0058] Specifically, when the mixed actinide salt is a plutonium nitrate pentahydrate solid and a thorium oxalate hexahydrate solid, 0.0<X≤0.1; when the mixed actinide salt is a thorium nitrate hexahydrate solid and a plutonium oxalate hexahydrate solid, 0.9≤X<1.0.

[0059] Optionally, in the mixed actinide salt, the tetravalent actinide nitrate is

[0060] U(NO 3 ) 4 3-4 hours 2 O solid, the tetravalent actinide oxalate is a solid thorium oxalate hexahydrate, or the tetravalent actinide nitrate is a solid thorium nitrate hexahydrate, and the tetravalent actinide oxalate is a solid U(IV) oxalate, the AnO 2 Type MOX fuel powder is (U x Th 1-x ) 2 powder;

[0061] Specifically, when the mixed actinide salt is U(NO 3 ) 4 3-4 hours 2 When the mixed actinide salt is a solid thorium nitrate hexahydrate and a solid thorium oxalate hexahydrate, 0.9≤X<1.0; when the mixed actinide salt is a solid thorium nitrate hexahydrate and a solid U(IV) oxalate, 0.0<X≤0.1.

[0062] Optionally, in the mixed actinide salt, the tetravalent actinide nitrate is

[0063] U(NO 3 ) 4 3-4 hours 2 O solid, the tetravalent actinide oxalate is plutonium oxalate hexahydrate solid, or the tetravalent actinide nitrate is plutonium nitrate pentahydrate, and the tetravalent actinide oxalate is U(IV) oxalate solid, the AnO 2Type MOX fuel powder is (U x Pu 1-x ) 2 powder;

[0064] When the mixed actinide salt is U(NO 3 ) 4 3-4 hours 2 When the mixed actinide salt is a plutonium nitrate pentahydrate solid and a U(IV) oxalate solid, 0.0<X≤0.1.

[0065] The specific implementation modes of the present invention are further described below through examples.

[0066] Example 1: Preparation of tetravalent actinide mixed salt eutectic

[0067] S11, preparation of mixed actinide eutectic: first, 0.6180g (0.990mmol) of dry thorium nitrate hexahydrate solid, 0.0492g (0.096mmol) of thorium oxalate hexahydrate solid and 0.6218g (10.353mmol) of urea solid were placed in a transparent glass bottle. During the mixing process, the solid powder softened and gradually liquefied. The glass bottle was gently shaken to mix the sample thoroughly. After heating on a hot plate at 80-100°C for about 5-10 minutes, there were still a small amount of insoluble particles in the mixture. 60 microliters of deionized water were added and ultrasonicated for 5 minutes. The mixture became a completely clear liquid, and an An(IV) type nitrate-oxalate mixed actinide eutectic containing An(IV) oxalate with an incorporation amount of 8.84At% (atomic percentage) was obtained;

[0068] Optionally, when the sample amount of the mixed actinide eutectic to be prepared is large, the mixture may be ground in a mortar and mixed with stirring.

[0069] For the MOX fuel to be prepared (such as ThO 2 Mixed with a small amount of PuO 2 The method provided in this embodiment is applicable to a mixed actinide salt raw material in which a small amount of tetravalent actinide oxalate (10% or less) is mixed into all tetravalent actinide nitrates to prepare a low eutectic.

[0070] Example 2: Eutectic AnO 2 Example of preparation of MOX fuel powder

[0071] S21. Preparation of mixed actinide eutectic: In an oxygen-free glove box, first take 0.5009 g of dry

[0072] (0.90-0.93mmol) nitric acid U(NO 3) 4 3-4 hours 2 O solid, 0.0526 (0.10 mmol) of thorium oxalate hexahydrate solid and 0.5587 g (9.30 mmol) of urea solid were placed in a transparent glass bottle. During the mixing process, the solid powder softened and gradually liquefied. The glass bottle was gently shaken to mix the sample thoroughly. After heating on a hot plate at 80-100° C. for about 5-10 minutes, the mixture became a completely clear liquid, thus obtaining an An(IV) type nitrate-oxalate mixed actinide eutectic containing An(IV) oxalate with an incorporation amount of 9.97-10.3 At% (atomic percentage);

[0073] Optionally, when the sample amount of the mixed actinide eutectic to be prepared is large, the mixture may be ground in a mortar and mixed with stirring.

[0074] S22, deamination: use a pipette to draw 20 μl of 9.0At% An(IV) type nitrate-oxalate mixed actinide eutectic into a crucible, heat the liquid to 150-160°C at a heating rate of 5-10°C / min under an argon atmosphere for 30 min to remove urea therein, wherein the actinide nitrate also removes part of the nitrate, and the obtained deamination powder is a powder of mixed actinide salt + part of actinide oxide;

[0075] S23, denitrification / decarbonization: The deaminated powder is heated to 500-800°C at a heating rate of 5-10°C / min in an argon atmosphere and kept at this temperature for more than 30 minutes to fully decompose the actinide nitrate and actinide oxalate in the mixed actinide salt in the deaminated powder. The denitrification / decarbonization powder (i.e., AnO 2 Type MOX fuel powder) is (U x Th 1-x ) 2 Type powder.

[0076] The AnO obtained in Example 1 2 The results of elemental surface distribution analysis of MOX fuel powder by scanning electron microscope-energy spectrum are shown in the figure below. Figure 3 shown. Figure 3 The analysis results show that the AnO prepared in Example 2 2 UO in MOX fuel powder 2 and ThO 2 The powder particles are evenly distributed, which indicates that the AnO 2 The chemical composition of MOX fuel powder is uniform and is evenly mixed at the microscopic molecular level.

[0077] Using the AnO provided in this embodiment 2The preparation method of MOX fuel powder can prepare AnO 2 For example, by using vibration dispersion method, microfluidics method, two-phase dispersion method or aerosol spray method, monodisperse AnO with a controllable particle size range of 1 μm to 1 mm and a narrow particle size distribution range can be prepared. 2 MOX microspheres are used in TRISO fuel and other applications as a new, economical and green AnO 2 Preparation scheme of MOX microspheres. 2 The preparation scheme of MOX fuel powder can also be extended to all tetravalent actinide nitrate and tetravalent actinide oxalate systems.

[0078] The method described in the present invention is not limited to the specific embodiments described. The above embodiments are only examples of the present invention. The present invention can also be implemented in other specific ways or other specific forms without departing from the gist or essential features of the present invention. Therefore, the described embodiments should be regarded as illustrative rather than restrictive in any respect. The scope of the present invention should be described by the attached claims, and any changes equivalent to the intent and scope of the claims should also be included in the scope of the present invention.

Claims

1. A method for preparing AnO2 type MOX fuel powder, characterized in that: The method comprises the following steps: S1. preparing a mixed actinide eutectic: mixing a dry mixed actinide salt with urea solid in a certain proportion until the mixture becomes a completely clear liquid, thereby obtaining a mixed actinide eutectic; the mixed actinide salt comprises tetravalent actinide nitrate and tetravalent actinide oxalate; S2, deamination: the mixed actinide eutectic is heated to a specified temperature according to a specified procedure and kept at the temperature for a specified time to obtain a deamination powder, wherein the deamination powder comprises a mixed actinide salt and an actinide oxide; S3, denitrification / decarbonization: the deamination powder is heated to a set temperature according to a set program and kept at that temperature for a set time, and the obtained denitrification / decarbonization powder is AnO2 type MOX fuel powder.

2. The method for preparing AnO2 type MOX fuel powder according to claim 1, characterized in that: The tetravalent actinide nitrate is solid plutonium nitrate pentahydrate, solid thorium nitrate hexahydrate or U(NO3)4·3-4H2O, and the tetravalent actinide oxalate is solid thorium oxalate hexahydrate, solid plutonium oxalate hexahydrate or U(IV) oxalate solid.

3. The method for preparing AnO2 type MOX fuel powder according to claim 1, 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 AnO2 type MOX fuel powder according to claim 1, characterized in that: In step S1, during the mixing of the mixed actinide salt and the urea solid, the mixture is mixed by stirring and / or grinding the mixture.

5. The method for preparing AnO2 type MOX fuel powder according to claim 4, characterized in that: In step S1, during the mixing of the mixed actinide salt and the urea solid, the mixed actinide salt and the urea solid are heated to obtain a completely clarified mixed actinide eutectic; When insoluble matter still exists in the mixture formed by the mixed actinide salt and urea after heating, deionized water is added to the mixture and ultrasonic treatment is performed to obtain a completely clarified mixed actinide eutectic.

6. The method for preparing AnO2 type MOX fuel powder according to claim 1, characterized in that: Step S2 includes the following specific steps: sucking the mixed actinide eutectic into a crucible by a pipette, and heating the crucible to 150-160° C. according to a specified program and keeping the temperature for more than 30 minutes to obtain the deaminated powder.

7. The method for preparing AnO2 type MOX fuel powder according to claim 1, characterized in that: In step S2, the deamination process is carried out under air or argon atmosphere; The specified procedure refers to a specified heating rate, and the specified heating rate is 5-10°C / min.

8. The method for preparing AnO2 type MOX fuel powder according to claim 1, characterized in that: In step S3, the deaminated powder is heated to 500-800° C. according to a set program and kept at this temperature for more than 30 minutes to obtain AnO2 type MOX fuel powder.

9. The method for preparing AnO2 type MOX fuel powder according to claim 1, characterized in that: In step S3, the denitrification / decarburization process is carried out under air or argon atmosphere; The setting procedure refers to the setting heating rate, and the setting heating rate is 5-10°C / min.

10. The method for preparing AnO2 type MOX fuel powder according to claim 2, characterized in that: When the mixed actinide salt is a solid plutonium nitrate pentahydrate and a solid thorium oxalate hexahydrate, or the mixed actinide salt is a solid thorium nitrate hexahydrate and a solid plutonium oxalate hexahydrate, the AnO2 type MOX fuel powder is (Th x Pu 1-x )O2 powder; When the mixed actinide salt is a solid plutonium nitrate pentahydrate and a solid thorium oxalate hexahydrate, 0.0<X≤0.1; when the mixed actinide salt is a solid thorium nitrate hexahydrate and a solid plutonium oxalate hexahydrate, 0.9≤X<1.

0.

11. The method for preparing AnO2 type MOX fuel powder according to claim 2, characterized in that: When the mixed actinide salt is U(NO3)4·3-4H2O solid and thorium oxalate hexahydrate solid, or the mixed actinide salt is thorium nitrate hexahydrate solid and U(IV) oxalate solid, the AnO2 type MOX fuel powder is (U x Th 1-x )O2 powder; When the mixed actinide salt is U(NO3)4·3-4H2O solid and thorium oxalate hexahydrate solid, 0.9≤X<1.0; when the mixed actinide salt is thorium nitrate hexahydrate solid and U(IV) oxalate solid, 0.0<X≤0.

1.

12. The method for preparing AnO2 type MOX fuel powder according to claim 2, characterized in that: When the mixed actinide salt is U(NO3)4·3-4H2O solid and plutonium oxalate hexahydrate solid, or the mixed actinide salt is plutonium nitrate pentahydrate and U(IV) oxalate solid, the AnO2 type MOX fuel powder is (U x Pu 1-x )O2 powder; When the mixed actinide salt is U(NO3)4·3-4H2O solid and plutonium oxalate hexahydrate solid, 0.9≤X<1.0; when the mixed actinide salt is plutonium nitrate pentahydrate solid and U(IV) oxalate solid, 0.0<X≤0.1.

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