A method for detecting purity of a uranium trifluoride powder

Abstract

This invention relates to a method for detecting the purity of UF3 powder, comprising the following steps: S1, preparing a (Ce(SO4)2) matrix uranium standard solution; S2, obtaining a uranium content standard curve; S3, providing the first UF3 powder to be tested, and determining whether it belongs to the first or second reaction according to the reaction equation; S4, if it is the second reaction, obtaining the first and second solutions; otherwise, obtaining the first solution; S5, if it is the second reaction, filtering and digesting the first and second solutions to prepare the third and fourth solutions respectively; otherwise, preparing the third solution; S6, if it is the second reaction, obtaining the uranium content in the third and fourth solutions based on the standard curve; otherwise, obtaining the uranium content in the third solution; S7, if it is the second reaction, calculating according to formula (2); otherwise, calculating according to formula (1). This invention improves the precision and accuracy of the detection results, providing important technical support for the practical application of UF3 powder.

Description

Technical Field

[0001] This invention relates to nuclear fuel, and more specifically to a method for detecting the purity of uranium trifluoride powder. Background Technology

[0002] Uranium trifluoride (UF3) possesses reducing properties and plays a crucial role in fluoride molten salt reactors. For example, in a novel process for preparing fuel salt for molten salt reactors (patent title: A Method for Fuel Reconstruction in Molten Salt Reactors, authorization number: CN109637682B), UF3 serves as an intermediate product, inhibiting system corrosion and improving process economics. Furthermore, introducing a small amount of UF3 during molten salt reactor operation can suppress the oxidizing properties of liquid fuel salts, thus ensuring the safe operation of the reactor vessel (Molten-salt reactor chemistry. Nuclear applications & technology, 1970, 8: 137-55.). Typically, UF3 is produced by reacting reducing agents (such as hydrogen, metallic uranium, silicon powder, uranium hydride, and aluminum powder) with uranium tetrafluoride (UF4) at high temperatures. The purity of UF3 powder is a critical indicator affecting its industrial-scale production and practical application.

[0003] Researchers have developed several methods for detecting the purity of UF3 powder for different preparation methods.

[0004] In 1955, Ross et al. used methylene blue titration to determine the concentration of U... 3+ The system can detect ions, but it is susceptible to interference from O2 in the air, and dry ice is required throughout the process to maintain an oxygen-free environment inside the reaction vessel.

[0005] In 1960, Rodden used hydrofluoric acid to suppress the reaction of UF3 with dilute hydrochloric acid to produce hydrogen gas, and determined the content of UF3 by the generated H2. However, quantitative detection of H2 requires additional complex equipment and is complicated to operate.

[0006] In 1964, Domingues attempted to directionally convert the remaining metallic uranium into U3O8 when reducing UF4 with metallic uranium, and then inferred the yield of UF3 based on the mass change. However, due to the wide variety of uranium oxides and their temperature sensitivity, this method was not accurate enough.

[0007] In 1981, Wijbenga synthesized UF3 from UF4 and UH3 at relatively low temperatures (700-900 K) and determined the purity of the prepared sample by comparing its XRD pattern with that of UF3 with known UF4 content. However, this method is affected by sample preparation and data analysis methods.

[0008] In summary, there is currently no mature method for detecting the purity of UF3 powder, which has become a prominent factor restricting the research and development and practical application of UF3 powder. Summary of the Invention

[0009] The purpose of this invention is to provide a method for detecting the purity of UF3 powder, thereby solving the problems of harsh operating conditions, poor operability, poor universality and poor testing accuracy in the existing technology.

[0010] To solve the above problems, the present invention adopts the following technical solution:

[0011] According to the present invention, a method for detecting the purity of UF3 powder includes the following steps: S1, preparing a uranium standard solution based on cerium sulfate (Ce(SO4)2); S2, detecting the uranium content in the uranium standard solution using an instrument to obtain a standard curve of uranium content based on Ce(SO4)2; S3, providing a first UF3 powder to be tested; determining the reducing agent based on the reaction equation of its preparation process; if the reducing agent is not a uranium-containing substance, it belongs to the first reaction; if the reducing agent is a uranium-containing substance, it belongs to the second reaction; S4, if the reaction described in S3 is determined to be the second reaction, grinding and sieving the first UF3 powder to be tested to obtain a second UF3 powder of micron-sized size, adding the second UF3 powder to be tested to freshly prepared Ce(SO4)2 solution for dissolution, and sequentially obtaining the first solution and the second solution using a separation method based on the difference in dissolution rates of UF3 and UF4; if the reaction described in S3 is determined to be the first reaction, only the first solution needs to be obtained according to the above steps; S5, if the reaction described in S3 is determined to be the second reaction... In the reaction, the first and second solutions are filtered and digested to prepare a clear and stable third and fourth solution, respectively. If the reaction described in S3 is determined to be the first type of reaction, the third solution only needs to be prepared according to the above steps. In S6, if the reaction described in S3 is determined to be the second type of reaction, based on the standard curve of uranium content in Ce(SO4)2 matrix in step S2, the uranium content in the third and fourth solutions is detected by an instrument, and the uranium content in the third and fourth solutions is obtained respectively. If the reaction described in S3 is determined to be the first type of reaction, the uranium content in the third solution only needs to be obtained according to the above steps. In S7, if the reaction is determined to be the second type of reaction in step S3, the purity of the UF3 product is calculated according to the formula based on the uranium content in the third and fourth solutions and the reaction equation in step S3. If the reaction is determined to be the first type of reaction in step S3, the purity of the UF3 product is calculated according to the formula (1) based on the uranium content in the third solution. The calculation in step S7 includes: assuming the molecular weight of UF3 is M UF3 The molecular weight of uranium is M. UIn preparing the first and second solutions, let m0 be the amount of the second powder to be tested; let V1 be the volume of the fifth solution and C1 be the uranium content; let V2 be the volume of the sixth solution and C2 be the uranium content. If the reaction is determined to be the first type of reaction in step S3, the purity TUP1 of the UF3 product is calculated according to formula (1).

[0012]

[0013] If the reaction is determined to be the second type of reaction in step S3, the purity of the UF3 product TUP2 is calculated according to formula (2).

[0014]

[0015] It should be understood that the instruments used in steps S2 and S6 are the same. Preferably, the instruments used in the above steps include inductively coupled plasma optical emission spectrometry (ICP-OES), X-ray fluorescence spectrometry (XRF), and potentiometric titrator (PMT).

[0016] Preferably, step S1 includes the following sub-steps: 1) dissolving a certain amount of Ce(SO4)2 powder in a solution containing inorganic acid to prepare a Ce(SO4)2 solution for later use; 2) mixing the Ce(SO4)2 solution and a nitric acid-based uranium standard solution to prepare a Ce(SO4)2-based uranium standard solution; or 2') adding UF3 single crystals to the Ce(SO4)2 solution, followed by adding nitric acid for digestion to obtain a Ce(SO4)2-based uranium standard solution; wherein the inorganic acid in the Ce(SO4)2 solution includes hydrochloric acid and sulfuric acid, the content of the inorganic acid is 0.5-3 mol / L, and the content of the Ce(SO4)2 solution is 0.01-0.1 mol / L; preferably, the Ce(SO4)2-based uranium standard solution includes at least three concentrations.

[0017] It should be understood that in step S1, the nitrate-based uranium standard solution is obtained by digesting uranium standard materials. Preferably, the uranium standard materials include uranium trioxide (U3O8), uranium trifluoride (UF3) single crystals, and lithium uranium pentafluorocarbonate (LiUF5) single crystals.

[0018] Preferably, the correlation coefficient of the uranium content standard curve in step S2 is 0.999 or higher.

[0019] Preferably, the reaction equation in step S3 mainly includes:

[0020] 2UF4 + H2 = 2UF3 + 2HF↑ (1)

[0021] 4UF4+Si=4UF3+SiF4↑ (2)

[0022] 3UF4 + Al = 3UF3 + AlF3 (3)

[0023] 3UF4 + U = 4UF3 (4) 6UF4 + 2UH3 = 8UF3 + 3H2↑ (5); The reducing agent is determined based on the reaction equations of its preparation process. If the reducing agent is not a uranium-containing substance, it belongs to the first type of reaction; if the reducing agent is a uranium-containing substance, it belongs to the second type of reaction. It should be understood that the above reaction equations are only examples for determination and are not a limitation. Step S3 mainly limits the determination of the reducing agent.

[0024] Step S4 includes: if the reaction is determined to be the second type of reaction in step S3, the first powder of UF3 to be tested is ground, and the second powder of UF3 to be tested with a micron-sized particle size is sieved using a microporous mesh sieve. This operation is repeated until the first powder is completely converted into the second powder; a certain amount of the second powder of UF3 to be tested is weighed and added to a freshly prepared Ce(SO4)2 solution, and the solution is shaken for 10s to 10min to dissolve the UF3 and obtain the first solution; the same mass of the second powder of UF3 to be tested is weighed and added to a freshly prepared Ce(SO4)2 solution, and left for 5 to 12h to obtain the second solution; if the reaction described in S3 is determined to be the first type of reaction, only the above steps are needed to obtain the first solution.

[0025] It should be understood that the Ce(SO4)2 solution used in step S4 should be consistent with the Ce(SO4)2 solution used in step S1, including the type and concentration of the inorganic acid used, and the Ce(SO4)2 concentration; the mass ratio of the Ce(SO4)2 solution to the powder to be tested is greater than or equal to 50:1.

[0026] Preferably, the micron-sized powder in step S4 is less than or equal to 50 μm. We have found that if the powder to be tested is not ground and sieved, it will affect the dissolution and separation of UF3 in the powder, thus causing a large deviation in the purity test results of the powder.

[0027] Preferably, in step S4, the mass ratio of Ce(SO4)2 solution to the test powder is greater than or equal to 50:1; the shaking dissolution time is 10s to 10min. We found that when the dissolution time exceeds 10min, if the test powder contains UF4, it dissolves into the Ce(SO4)2 solution, causing a significant positive deviation in the purity test results of the test powder.

[0028] Preferably, step S5 includes: if the reaction in S3 is determined to be a second reaction, filtering the first solution using a microporous membrane and transferring it to a digestion tube, then adding hydrogen peroxide and concentrated nitric acid to the digestion tube, and heating the digestion tube to digest it, thus preparing a third solution. The second solution is then used to prepare a fourth solution using the same procedure. If the reaction in S3 is determined to be a first reaction, only the above steps are needed to prepare the third solution. Preferably, the pore size of the microporous membrane is less than or equal to 0.45 μm; the added hydrogen peroxide content in the digestion solution is 1–3 mol / L; the added nitric acid content in the digestion solution is 1–3 mol / L. We found that the third and fourth solutions prepared according to the above steps both have high stability, can be left at room temperature for more than 7 days without significant changes, and do not produce significant deviations in the uranium content test of the sample.

[0029] It should be understood that the digestion in step S5 is the same as the digestion in step S1, which is a process of dissolving substances by heating in a nitric acid system. The heating method during digestion includes resistance heating or microwave heating. Preferably, when using resistance heating, the temperature is 80-95°C and the digestion time is 5-12 hours. When using microwave heating, the temperature is 120-180°C and the digestion time is 0.5-3 hours.

[0030] Preferably, step S6 includes: if the reaction described in S3 is determined to be a second type of reaction, (1) based on theoretical calculations, when the uranium content in the third and fourth solutions is greater than or equal to 100 mg / L, the uranium content in the solutions can be directly tested using PMT or XRF; (2) when the uranium content in the third and fourth solutions is less than 100 mg / L, deionized water is added to the third and fourth solutions respectively to dilute the uranium content in the third and fourth solutions to 1-10 mg / L, and then the uranium content in the solutions is tested using ICP-OES or XRF. If the reaction described in S3 is determined to be a first type of reaction, it is only necessary to test the uranium content in the third solution according to the above steps.

[0031] It should be understood that the uranium content is classified and tested using instruments based on the theoretically calculated uranium content in the solution. (1) According to theoretical calculations, when the uranium content in the solution is greater than or equal to 100 mg / L, the uranium content in the solution can be directly tested using PMT or XRF; (2) According to theoretical calculations, when the uranium content in the solution is 1 to 10 mg / L, the uranium content in the solution can be tested using ICP-OES or XRF.

[0032] In summary, the UF3 powder purity detection method provided by this invention employs a separation method based on differences in dissolution rates, enabling rapid and convenient separation of the test solution containing dissolved UF3, thus providing a foundation for UF3 content detection. In particular, this invention is universal and simple; a single detection procedure and conventional instruments can easily detect the purity of UF3 products prepared by various existing methods. Furthermore, the method described in this invention significantly overcomes the limitations of stringent experimental conditions and specialized equipment required by existing detection methods, improving the efficiency of UF3 powder purity detection and providing a foundation for quality control and practical application in the industrial preparation of UF3 powder. Attached Figure Description

[0033] Figure 1 This is a flowchart of a method for detecting the purity of UF3 powder according to the present invention. Detailed Implementation

[0034] The present invention will be further described below with reference to specific embodiments. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. The invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to make the disclosure of the invention more thorough and complete.

[0035] Example 1 Determination of purity of UF3 powder prepared by chemical reaction (1)

[0036] First, a Ce(SO4)2-based uranium standard solution was prepared. Ce(SO4)2 powder and H2SO4 (98% by mass) were mixed, and deionized water was added to adjust the Ce(SO4)2 and H2SO4 content in the solution, resulting in a Ce(SO4)2 solution (with Ce(SO4)2 and H2SO4 contents of 0.1M and 3M, respectively). U3O8 powder, HNO3 (65% by mass), H2O2 (30% by mass), and deionized water were mixed and digested using resistance heating to obtain an HNO3-based uranium standard solution (1% uranium content). Based on theoretical calculations, the above Ce(SO4)2 solution and the HNO3-based uranium standard solution (1% uranium content) were mixed to prepare three Ce(SO4)2-based uranium standard solutions with uranium contents of 0.1%, 0.3%, and 0.5%, respectively.

[0037] The uranium content in the Ce(SO4)2 matrix uranium standard solution was determined by PMT, and a uranium content standard curve was obtained with a correlation coefficient of 0.9998.

[0038] The UF3 powder prepared by chemical reaction (1) is given. Its chemical equation is 2UF4+H2=2UF3+2HF↑(1). Therefore, it is determined that the reaction belongs to the first type of reaction.

[0039] After grinding the first UF3 powder to be tested, the second UF3 powder with a size of less than 50 μm was obtained by sieving with a microporous mesh sieve. This operation was repeated until the first powder was completely converted into the second powder. 0.1 g of the second UF3 powder to be tested was weighed and added to 4 mL of freshly prepared Ce(SO4)2 solution. The solution was shaken for 10 min to dissolve the UF3 and obtain the first solution.

[0040] The first solution was filtered through a 0.45 μm microporous membrane and then transferred to a digestion tube. HNO3 (65% by mass) and H2O2 (30% by mass) were then added to the digestion tube, and the tube was heated for digestion to produce 12 mL of a clear and stable third solution.

[0041] The uranium content in the solution was determined to be 0.429% using PMT testing.

[0042] The purity of UF3 powder in this experiment was calculated to be 68% using formula (1).

[0043] Example 2 Determination of the purity of UF3 powder prepared by chemical reaction (2)

[0044] First, a Ce(SO4)2-based uranium standard solution was prepared, including the following steps: 1) Ce(SO4)2 powder and H2SO4 (98% by mass) were mixed, and deionized water was added to adjust the Ce(SO4)2 and H2SO4 content in the solution to obtain a Ce(SO4)2 solution (with Ce(SO4)2 and H2SO4 contents of 0.09M and 2.5M, respectively); 2) LiUF5 single crystal, HNO3 (65% by mass), H2O2 (30% by mass) and deionized water were mixed and digested by resistance heating to obtain an HNO3-based uranium standard solution (uranium content of 1%); 3) Based on theoretical calculations, the above Ce(SO4)2 solution and HNO3-based uranium standard solution (uranium content of 1%) were mixed to prepare three Ce(SO4)2-based uranium standard solutions with uranium contents of 0.1%, 0.2% and 0.4%, respectively.

[0045] The uranium content in the Ce(SO4)2 matrix uranium standard solution was detected by XRF, and a uranium content standard curve was obtained with a correlation coefficient of 0.9999.

[0046] The UF3 powder prepared by chemical reaction (2) is given by chemical equation 4UF4+Si=4UF3+SiF4↑(2), and it is determined that the reaction belongs to the first type of reaction.

[0047] After grinding the first UF3 powder to be tested, the second UF3 powder with a size of less than 40 μm was sieved using a microporous mesh sieve. This operation was repeated until the first powder was completely converted into the second powder. 0.1 g of the second UF3 powder to be tested was weighed and added to 5 mL of freshly prepared Ce(SO4)2 solution. The solution was shaken for 5 min to dissolve the UF3 and obtain the first solution.

[0048] The first solution was filtered through a 0.22 μm microporous membrane and transferred to a digestion tube. Then, HNO3 (65% by mass) and H2O2 (30% by mass) were added to the digestion tube, and the tube was heated for digestion to prepare 15 mL of clear and stable third solution.

[0049] XRF analysis showed that the uranium content in the solution was 0.353%.

[0050] The purity of UF3 powder in this experiment was calculated to be 70% using formula (1).

[0051] Example 3 Determination of the purity of UF3 powder prepared by chemical reaction (3)

[0052] First, a Ce(SO4)2-based uranium standard solution was prepared. Ce(SO4)2 powder and H2SO4 (98% by mass) were mixed, and deionized water was added to adjust the Ce(SO4)2 and H2SO4 concentrations, resulting in a Ce(SO4)2 solution (with Ce(SO4)2 and H2SO4 concentrations of 0.03 M and 1.6 M, respectively). UF3 single crystals, HNO3 (65% by mass), H2O2 (30% by mass), and deionized water were mixed and digested using resistance heating to obtain an HNO3-based uranium standard solution (uranium concentration of 20 mg / L). Based on theoretical calculations, the above Ce(SO4)2 solution and the HNO3-based uranium standard solution (uranium concentration of 20 mg / L) were mixed to prepare three Ce(SO4)2-based uranium standard solutions with uranium concentrations of 1 mg / L, 2 mg / L, and 4 mg / L, respectively.

[0053] The uranium content in the Ce(SO4)2 matrix uranium standard solution was determined by ICP-OES, and a uranium content standard curve was obtained with a correlation coefficient of 0.9999.

[0054] The UF3 powder prepared by chemical reaction (3) is provided, and its chemical equation is 3UF4+Al=3UF3+AlF3(3); it is thus determined that the reaction belongs to the first type of reaction.

[0055] After grinding the first UF3 powder to be tested, the second UF3 powder with a size of less than 30 μm was sieved using a microporous mesh sieve. This operation was repeated until the first powder was completely converted into the second powder. 0.05 g of the second UF3 powder to be tested was weighed and added to 5 mL of freshly prepared Ce(SO4)2 solution. The solution was shaken for 1 min to dissolve the UF3 and obtain the first solution.

[0056] The first solution was filtered through a 0.20 μm microporous membrane and transferred to a digestion tube. Then, HNO3 (65% by mass) and H2O2 (30% by mass) were added to the digestion tube, and the tube was heated for digestion to prepare 15 mL of clear and stable third solution.

[0057] Take 1 mL of the third solution and dilute it with deionized water to 100 mL to obtain the first diluted solution of the third solution. Take another 1 mL of this diluted solution and dilute it with deionized water to 10 mL to obtain the second diluted solution of the third solution (equivalent to a total volume of 1 L for the diluted solutions). The uranium content in the second diluted solution of the third solution was tested using ICP-OES, and the result was 2.26 mg / L. Therefore, the uranium content in the third solution is 2.26 mg / mL.

[0058] The purity of UF3 powder in this experiment was calculated to be 89.5% using formula (1).

[0059] Example 4: Determination of the purity of UF3 powder prepared by chemical reaction (4)

[0060] First, a Ce(SO4)2-based uranium standard solution was prepared. Ce(SO4)2 powder and H2SO4 (98% by mass) were mixed, and deionized water was added to adjust the Ce(SO4)2 and H2SO4 content in the solution, resulting in a Ce(SO4)2 solution (with Ce(SO4)2 and H2SO4 contents of 0.07M and 2M, respectively). U3O8 powder, HNO3 (65% by mass), H2O2 (30% by mass), and deionized water were mixed and digested using resistance heating to obtain an HNO3-based uranium standard solution (1% uranium content). Based on theoretical calculations, the above Ce(SO4)2 solution and the HNO3-based uranium standard solution (1% uranium content) were mixed to prepare three Ce(SO4)2-based uranium standard solutions with uranium contents of 0.1%, 0.2%, and 0.4%, respectively.

[0061] The uranium content in the Ce(SO4)2 matrix uranium standard solution was detected by PMT, and a uranium content standard curve was obtained with a correlation coefficient of 0.9999.

[0062] The UF3 powder prepared by chemical reaction (4) is given, and its chemical equation is 3UF4+U=4UF3(4). Therefore, it is determined that the reaction belongs to the second type of reaction.

[0063] After grinding the first UF3 powder to be tested, the second UF3 powder with a size smaller than 25 μm was sieved using a microporous mesh sieve. This operation was repeated until the first powder was completely converted into the second powder. 0.05 g of the second UF3 powder to be tested was weighed and added to 5 mL of freshly prepared Ce(SO4)2 solution. The solution was shaken for 30 s to dissolve the UF3, obtaining the first solution. 0.05 g of the second UF3 powder to be tested was then weighed and added to the freshly prepared Ce(SO4)2 solution, and allowed to stand for 5 h to obtain the second solution.

[0064] The first solution was filtered through a 0.22 μm microporous membrane and transferred to a digestion tube. Then, HNO3 (65% by mass) and H2O2 (30% by mass) were added to the digestion tube, and the solution was heated for digestion. The volume was then adjusted to 10 mL to prepare a clear and stable third solution. The same procedure was used to prepare a 10 mL clear and stable fourth solution from the second solution.

[0065] PMT tests showed that the uranium content in the third and fourth solutions was 0.3760% and 0.3791%, respectively.

[0066] The purity of UF3 powder in this experiment was calculated to be 98.9% using formula (2).

[0067] Example 5: Determination of the purity of UF3 powder prepared by chemical reaction (5)

[0068] First, a Ce(SO4)2-based uranium standard solution was prepared. Ce(SO4)2 powder and H2SO4 (98% by mass) were mixed, and deionized water was added to adjust the Ce(SO4)2 and H2SO4 concentrations, resulting in a Ce(SO4)2 solution (with Ce(SO4)2 and H2SO4 concentrations of 0.01 M and 0.5 M, respectively). UF3 single crystals, HNO3 (65% by mass), H2O2 (30% by mass), and deionized water were mixed and digested using resistance heating to obtain an HNO3-based uranium standard solution (uranium concentration of 40 mg / L). Based on theoretical calculations, the above Ce(SO4)2 solution and the HNO3-based uranium standard solution (uranium concentration of 40 mg / L) were mixed to prepare three Ce(SO4)2-based uranium standard solutions with uranium concentrations of 1 mg / L, 2 mg / L, and 4 mg / L, respectively.

[0069] The uranium content in the Ce(SO4)2 matrix uranium standard solution was determined by ICP-OES, and a uranium content standard curve was obtained with a correlation coefficient of 0.9999.

[0070] The UF3 powder prepared by chemical reaction (5) is given by chemical equation 6UF4+2UH3=8UF3+3H2↑ (5), and it is determined that the reaction belongs to the second type of reaction.

[0071] After grinding the first UF3 powder to be tested, the second UF3 powder with a size smaller than 20 μm was sieved using a microporous mesh sieve. This operation was repeated until the first powder was completely converted into the second powder. 0.05 g of the second UF3 powder to be tested was weighed and added to 5 mL of freshly prepared Ce(SO4)2 solution. The solution was shaken for 1 min to dissolve the UF3 and obtain the first solution. 0.05 g of the second UF3 powder to be tested was then weighed and added to the freshly prepared Ce(SO4)2 solution, and allowed to stand for 8 h to obtain the second solution.

[0072] The first solution was filtered through a 0.20 μm microporous membrane and transferred to a digestion tube. Then, HNO3 (65% by mass) and H2O2 (30% by mass) were added to the digestion tube, and the tube was heated for digestion to prepare 12 mL of a clear and stable third solution. The same procedure was used to prepare a fourth solution, also 12 mL of clear and stable, from the second solution.

[0073] Take 1 mL of the third solution and dilute it with deionized water to 100 mL to obtain the first diluted solution of the third solution. Further take 1 mL of the first diluted solution of the third solution and dilute it with deionized water to 10 mL to obtain the second diluted solution of the third solution (equivalent to a total volume of 1 L). Use the same procedure to prepare the second diluted solution of the fourth solution (equivalent to a total volume of 1 L). Use ICP-OES to test the uranium content in the second diluted solutions of the third and fourth solutions. The uranium content in the second diluted solutions of the third and fourth solutions is 3.156 mg / L and 3.158 mg / L, respectively. Therefore, the uranium content in the third and fourth solutions is 3.156 mg / mL and 3.158 mg / mL, respectively.

[0074] The purity of UF3 powder in this experiment was calculated to be 99.9% using formula (2).

[0075] Example 6: Determination of the purity of UF3 powder prepared by chemical reaction (5)

[0076] First, a Ce(SO4)2-based uranium standard solution was prepared. Ce(SO4)2 powder and H2SO4 (98% by mass) were mixed, and deionized water was added to adjust the Ce(SO4)2 and H2SO4 content in the solution, resulting in a Ce(SO4)2 solution (with Ce(SO4)2 and H2SO4 contents of 0.05M and 1.5M, respectively). A LiUF5 single crystal, HNO3 (65% by mass), H2O2 (30% by mass), and deionized water were mixed and digested using resistance heating to obtain an HNO3-based uranium standard solution (1% uranium content). Based on theoretical calculations, the above Ce(SO4)2 solution and the HNO3-based uranium standard solution (1% uranium content) were mixed to prepare three Ce(SO4)2-based uranium standard solutions with uranium contents of 0.1%, 0.2%, and 0.4%, respectively.

[0077] The uranium content in the Ce(SO4)2 matrix uranium standard solution was detected by XRF, and a uranium content standard curve was obtained with a correlation coefficient of 0.9999.

[0078] The UF3 powder prepared by chemical reaction (5) is given by chemical equation 6UF4+2UH3=8UF3+3H2↑ (5), and it is determined that the reaction belongs to the second type of reaction.

[0079] After grinding the first UF3 powder to be tested, the second UF3 powder with a size of less than 20 μm was sieved using a microporous mesh sieve. This operation was repeated until the first powder was completely converted into the second powder. 0.05 g of the second UF3 powder to be tested was weighed and added to 5 mL of freshly prepared Ce(SO4)2 solution. The solution was shaken for 30 s to dissolve the UF3, obtaining the first solution. 0.05 g of the second UF3 powder to be tested was then weighed and added to the freshly prepared Ce(SO4)2 solution, and allowed to stand for 12 h to obtain the second solution.

[0080] The first solution was filtered through a 0.22 μm microporous membrane and transferred to a digestion tube. Then, HNO3 (65% by mass) and H2O2 (30% by mass) were added to the digestion tube, and the tube was heated for digestion to prepare 10 mL of a clear and stable third solution. The same procedure was used to prepare a fourth solution, also 10 mL of clear and stable, from the second solution.

[0081] The uranium content in the third and fourth solutions was determined by ICP-OES, and the results showed that the uranium content in the third and fourth solutions was 0.3787% and 0.3789%, respectively.

[0082] The purity of UF3 powder in this experiment was calculated to be 99.9% using formula (2).

[0083] In summary, this invention employs a separation method based on the difference in dissolution rates between UF3 and UF4 to efficiently obtain the test solution containing dissolved UF3, thereby accurately determining the UF3 content in the sample. The detection method involved in this invention requires only simple operation and conventional instruments, and is applicable to the detection of the purity of UF3 powders prepared by various existing methods. Furthermore, this invention solves the problems of harsh operating conditions, poor operability, limited universality, and low testing accuracy in existing UF3 powder purity detection methods, improving the precision and accuracy of the detection results, facilitating promotion and application, and providing important technical support for the research and development and practical application of UF3 powder.

[0084] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the invention. Various variations can be made to the above embodiments of the present invention. That is, all simple and equivalent changes and modifications made based on the claims and description of this invention fall within the protection scope of the claims of this patent. All aspects not described in detail in this invention are conventional technical content.

Claims

1. A method for detecting the purity of UF3 powder, characterized in that, The detection method includes the following steps: S1, prepare Ce(SO4)2 matrix uranium standard solution; S2, the uranium content in the Ce(SO4)2 matrix uranium standard solution was detected by instrument, and a standard curve of uranium content in the Ce(SO4)2 matrix was obtained; S3 provides the reaction equation of the first powder of UF3 to be tested and its preparation process. The reducing agent is determined according to the reaction equation. If the reducing agent is a uranium-free substance, the reaction is determined to be the first type of reaction. If the reducing agent is a uranium-containing substance, the reaction is determined to be the second type of reaction. S4, if the reaction is determined to be the second type of reaction in step S3, grind and sieve the first UF3 powder to be tested to obtain a second UF3 powder with a micron-sized particle size. Add the second UF3 powder to be tested to freshly prepared Ce(SO4)2 solution for dissolution. Use a separation method based on the difference in dissolution rates between UF3 and UF4 to obtain the first solution and the second solution in sequence. If the reaction is determined to be the first type of reaction in step S3, only the first solution needs to be obtained according to the above steps. S5. If the reaction is determined to be the second type of reaction in step S3, the first and second solutions are filtered and digested to prepare a clear and stable third and fourth solution, respectively; if the reaction is determined to be the first type of reaction in step S3, the third solution is prepared by following the above steps. S6. If the reaction is determined to be the second type of reaction in step S3, based on the Ce(SO4)2 matrix uranium content standard curve in step S2, the uranium element in the third and fourth solutions is detected by instruments to obtain the uranium content in the third and fourth solutions respectively; if the reaction is determined to be the first type of reaction in step S3, the uranium content in the third solution only needs to be obtained by following the above steps. S7. If the reaction is determined to be the second type of reaction in step S3, the purity of the UF3 product is calculated according to the uranium content in the third and fourth solutions and the reaction equation in step S3. If the reaction is determined to be the first type of reaction in step S3, the purity of the UF3 product is calculated according to the uranium content in the third solution and the formula (1). The calculation in step S7 includes: assuming the molecular weight of UF3 is M. UF3 The molecular weight of uranium is M. U In preparing the first and second solutions, let m0 be the amount of the second powder to be tested; let V1 be the volume of the fifth solution and C1 be the uranium content; let V2 be the volume of the sixth solution and C2 be the uranium content. If the reaction is determined to be the first type of reaction in step S3, the purity TUP1 of the UF3 product is calculated according to formula (1). If the reaction is determined to be the second type of reaction in step S3, the purity of the UF3 product TUP2 is calculated according to formula (2).

2. The detection method according to claim 1, characterized in that, Step S1 includes the following sub-steps: 1) Dissolving a certain amount of Ce(SO4)2 powder in a solution containing inorganic acid to prepare a Ce(SO4)2 solution for later use; 2) Mixing the Ce(SO4)2 solution and a nitric acid-based uranium standard solution to prepare a Ce(SO4)2-based uranium standard solution; or 2') Adding UF3 single crystals to the Ce(SO4)2 solution, followed by adding nitric acid for digestion to obtain a Ce(SO4)2-based uranium standard solution; wherein the inorganic acid in the Ce(SO4)2 solution includes hydrochloric acid and sulfuric acid, the content of the inorganic acid is 0.5-3 mol / L, and the content of the Ce(SO4)2 solution is 0.01-0.1 mol / L; the Ce(SO4)2-based uranium standard solution includes at least three concentrations.

3. The detection method according to claim 2, characterized in that, In step S1, the nitrate-based uranium standard solution is obtained by digesting uranium standard materials with nitric acid and hydrogen peroxide; wherein, the uranium standard materials include U3O8, UF3 single crystal and LiUF5 single crystal.

4. The detection method according to claim 1, characterized in that, In step S2, the correlation coefficient of the uranium content standard curve is greater than 0.

999.

5. The detection method according to claim 2, characterized in that, Step S4 includes: if the reaction is determined to be the second type of reaction in step S3, the first powder of UF3 to be tested is ground, and the second powder of UF3 to be tested with a micron-sized particle size is sieved using a microporous mesh sieve. This operation is repeated until the first powder is completely converted into the second powder; a certain amount of the second powder of UF3 to be tested is weighed and added to a freshly prepared Ce(SO4)2 solution, and the solution is shaken for 10s to 10min to dissolve the UF3 and obtain the first solution; the same mass of the second powder of UF3 to be tested is weighed and added to a freshly prepared Ce(SO4)2 solution, and left for 5 to 12h to obtain the second solution; if the reaction described in S3 is determined to be the first type of reaction, only the above steps are needed to obtain the first solution.

6. The detection method according to claim 5, characterized in that, The Ce(SO4)2 solution used in step S4 should be the same as the Ce(SO4)2 solution used in step S1, including the type and concentration of the inorganic acid used and the Ce(SO4)2 concentration; the micron-level size in step S4 is less than or equal to 50 μm, and the mass ratio of the Ce(SO4)2 solution to the powder to be tested is greater than or equal to 50:

1.

7. The detection method according to claim 2, characterized in that, Step S5 includes: filtering the first solution using a microporous filter membrane and transferring it to a digestion tube, then adding hydrogen peroxide and concentrated nitric acid to the digestion tube, heating the digestion tube to digest it, and preparing a third solution; using the same operation to prepare a fourth solution from the second solution; wherein the pore size of the microporous filter membrane is less than or equal to 0.45 μm.

8. The detection method according to claim 7, characterized in that, The digestion in step S5 is the same as the digestion in step S1. The added hydrogen peroxide content in the digestion solution is 1-3 mol / L; the added nitric acid content in the digestion solution is 1-3 mol / L; the heating method during digestion includes resistance heating or microwave heating. When using resistance heating, the temperature is 80-95℃ and the digestion time is 5-12 hours. When using microwave heating, the temperature is 120-180℃ and the digestion time is 0.5-3 hours.

9. The detection method according to claim 1, characterized in that, The instruments used in steps S2 and S6 are the same instruments, and the test parameters of the instruments in steps S2 and S6 should be consistent. The instruments include inductively coupled plasma atomic emission spectrometer, X-ray fluorescence spectrometer, and potentiometric titrator.

10. The detection method according to claim 9, characterized in that, Step S6 includes: classifying the solutions according to the uranium content in the third and fourth solutions; 1) when the uranium content in the third and fourth solutions is greater than or equal to 100 mg / L, the uranium content in the solutions can be directly tested using a potentiometric titrator or X-ray fluorescence spectrometry; 2) when the uranium content in the third and fourth solutions is less than 100 mg / L, deionized water is added to the third and fourth solutions respectively to dilute the uranium content in the third and fourth solutions to 1-10 mg / L, and then the uranium content in the solutions is tested using inductively coupled plasma atomic emission spectrometry or X-ray fluorescence spectrometry.

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