Construction method of organic phase uranium working curve

Abstract

The invention relates to a construction method of an organic phase uranium working curve, which comprises the following steps: completely extracting uranium in a water phase uranium stock solution by adopting a 30vol% TBP-kerosene extraction technology, transferring the uranium into an organic phase, and determining the value of the uranium in the organic phase by combining an automatic potentiometric titrator and a trace uranium analyzer analysis technology. Compared with the prior art, the method provided by the invention is accurate and reliable and extremely good in uranium separation effect through theoretical and experimental verification, and can be used for indirect valuing of uranium in an organic phase, so that the recovery rate of uranium is effectively improved, and the method has important application value for closed circulation of nuclear fuel and reuse of uranium resources.

Description

Technical Field

[0001] The invention relates to the research field of nuclear fuel cycle analysis technology, in particular to a method for constructing an organic phase uranium working curve. Background Art

[0002] In order to achieve the dual carbon goals, my country is stepping up the development and utilization of nuclear energy, but the disposal of irradiated nuclear fuel is an important link that limits the sustainable development of nuclear energy. Considering that the direct disposal of these nuclear fuels will pose a risk of radiation pollution to the environment and will lead to the waste of uranium and plutonium resources, my country has adopted a closed nuclear fuel cycle policy to achieve the recovery and reuse of uranium and plutonium. Among them, uranium, as the main source of alpha radioactive toxicity, has irreversible harm to the environment and organisms and requires special attention. Uranium isotopes are also widely used in our lives, for example, 235 U and 233 U is a fissile nuclide and can be used as nuclear fuel; 238 U is a convertible material that can generate fissile nuclear material through the (n,γ) reaction 239 Pu; in addition, the rays produced by uranium decay can be used in medicine for sterilization, clinical diagnosis and treatment, etc.

[0003] Due to these characteristics and applications of uranium, it is very necessary to accurately analyze uranium in the closed cycle of nuclear fuel. At present, the analysis methods of uranium include spectrophotometry, ICP-MS (inductively coupled plasma mass spectrometry), XRF (X-ray fluorescence), L-edge densitometer, α-spectroscopy, etc. These methods require the use of standard solutions of uranium, among which the uranium standard in the aqueous phase can be obtained by dissolving and constant volume of the certified standard material U3O8 or by dissolving, constant volume, and automatic potentiometric titration of the reference standard material UO3. Automatic potentiometric titration is a method with very high accuracy and precision, and is less affected by external interference, but it is usually used for the analysis of uranium in aqueous solutions and is not applicable to the accurate determination of uranium in organic phases.

[0004] The determination of uranium in the organic phase has always been a key technology in the field of nuclear fuel closed cycle, and there is currently no particularly good means of determination. In order to ensure the recycling of uranium elements, it is urgent to develop a method to accurately determine the uranium content in the organic phase. Summary of the invention

[0005] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and provide a method for constructing an organic phase uranium working curve to achieve accurate determination of the uranium content in the organic phase.

[0006] During the course of conception, the applicant believed that the present invention uses 30 vol% tributyl phosphate-kerosene to extract uranium from aqueous uranium stock solution and then transfer it to the organic phase, and combines the automatic potentiometric titrator and trace uranium analyzer analysis technology to determine the uranium content in the organic phase. This method has an excellent uranium separation effect and is accurate and reliable as verified by theory and experiments.

[0007] The purpose of the present invention can be achieved by the following technical solutions:

[0008] A method for constructing an organic phase uranium working curve comprises the following steps:

[0009] S1. Preparation of aqueous uranium stock solution;

[0010] S2, preparation of 30 vol% tributyl phosphate-kerosene;

[0011] S3, using 30 vol% tributyl phosphate-kerosene prepared in S2 to extract the aqueous uranium stock solution prepared in S1 to prepare an organic uranium standard solution;

[0012] S4, determining and analyzing the concentration of uranium in the aqueous uranium stock solution prepared in S1 and the raffinate in S3;

[0013] S5. Calculation of the concentration of organic phase uranium standard solution and establishment of organic phase uranium standard curve.

[0014] Furthermore, in S1, the preparation of the aqueous uranium stock solution comprises:

[0015] Add 6-8 mol / L nitric acid to the U3O8 certified standard material or the UO3 reference standard material, heat on a hot plate for the first dissolution, evaporate to dryness after complete dissolution, add 6-8 mol / L nitric acid for the second dissolution and cool to room temperature, then transfer the solution to a volumetric flask, repeatedly wash the beaker three times with 4-6 mol / L nitric acid as a medium, transfer the solution to the volumetric flask, make up to volume with 4-6 mol / L nitric acid and shake well to obtain an aqueous uranium stock solution.

[0016] Among them, the aqueous uranium stock solution obtained using the U3O8 certified standard substance is the aqueous uranium standard solution, and the aqueous uranium stock solution obtained using the UO3 reference standard substance is the aqueous uranium solution.

[0017] Furthermore, the U3O8 certified standard material is GBW 04201.

[0018] Furthermore, the heating temperature is 230-290°C.

[0019] Further, in S2, the preparation of 30 vol% tributyl phosphate-kerosene comprises:

[0020] Tributyl phosphate was added to kerosene, and the mixture was washed three times with 5wt% Na2CO3 solution (1:1), washed with water until neutral, washed three times with 1mol / L nitric acid, and washed with water until neutral.

[0021] Furthermore, the volume ratio of tributyl phosphate to kerosene is 3:7.

[0022] Further, in S3, the aqueous uranium stock solution prepared in S1 is extracted with 30 vol% tributyl phosphate-kerosene prepared in S2 to prepare an organic uranium standard solution, comprising:

[0023] The aqueous uranium stock solution prepared in S1 was extracted with 30 vol% tributyl phosphate-kerosene prepared in S2, the residual solution was transferred to a volumetric flask, diluted to the mark with water, and then the extracted organic phase was transferred to another volumetric flask to make up the volume to obtain an organic uranium standard solution.

[0024] Furthermore, in S4, the concentration of uranium in the aqueous uranium stock solution prepared in S1 and the raffinate in S3 is determined and analyzed, including:

[0025] The aqueous uranium stock solution is titrated using an automatic potentiometric titrator, wherein the concentration of the aqueous uranium standard solution is known and does not need to be titrated; the uranium concentration in the raffinate is determined using a trace uranium analyzer;

[0026] When [UO2 2+ ] 原液 :[UO2 2+ ] 萃残液 ≥10000:1, it can be considered that all the uranium in the aqueous uranium solution is transferred to the organic phase.

[0027] Furthermore, in S5, the concentration of the organic phase uranium standard solution is calculated and the organic phase uranium standard curve is established by the following calculation formula:

[0028] [UO2 2+ ] 有机相 =[UO2 2+ ] 原液 / n

[0029] Where:

[0030] [UO2 2+ ] 有机相 is the concentration of uranium in the organic phase uranium standard solution, grams per liter (g / L);

[0031] [UO2 2+ ] stock solution is the concentration of uranium in the aqueous uranium stock solution, the aqueous uranium stock solution is an aqueous uranium standard solution or an aqueous uranium solution, grams per liter (g / L);

[0032] n is the dilution factor, i.e., the factor at which uranium is extracted from the aqueous phase into the organic phase, the organic phase solution is transferred to a volumetric flask, and the volume is fixed to the final volume with 30 vol% TBP-kerosene.

[0033] The organic phase uranium standard solution prepared by S3 was diluted step by step to obtain multiple groups of organic phase uranium standards. The concentrations of the multiple groups of organic phase uranium standards were measured by X-ray fluorescence spectrometer, and the organic phase uranium standard curve was established with the multiple groups of organic phase uranium standard concentrations as the abscissa and the integrated area of ​​light intensity as the ordinate.

[0034] Furthermore, uncertainty assessment is required when establishing the standard curve for organic uranium, including:

[0035] (1) Relative standard uncertainty u generated by standard reagents r (p):

[0036] The reagent purity of the standard substance U3O8 (GBW04021, National Center for Standard Material Research) used is (84.754±0.02)%, which is converted into standard uncertainty according to uniform distribution:

[0037]

[0038] (2) Relative standard uncertainty u generated by weighing r (m):

[0039] The uncertainty caused by balance calibration, the statutory allowable error for analytical balances that have passed metrological verification is 0.1 mg, which is converted into a standard uncertainty of 0.1 / 1.73=0.058 mg based on uniform distribution; referring to other analytical balances within 20g, the standard uncertainty of sample weight variability is ±0.07 mg.

[0040]

[0041] If the standard mass of U is weighed: 10.000g

[0042]

[0043] (3) Uncertainty component u generated by the preparation of uranium stock solution r (V):

[0044] ① Use a 10mL volumetric flask to prepare the organic phase uranium standard solution

[0045] The maximum allowable deviation of a 10mL volumetric flask is ±0.04mL. Considering uniform distribution, its standard uncertainty is

[0046]

[0047] The volume of the volumetric flask is V = 10 mL, and the volume expansion coefficient of water at 20°C is 2.1×10 -4 / ℃, the laboratory temperature is (20±5)℃, calculated according to normal distribution, taking k=2, the standard uncertainty is

[0048]

[0049] According to the above uncertainty components, the relative uncertainty u introduced by the 10mL volumetric flask is obtained. r (V 10 )for

[0050]

[0051] ② Use a 100mL volumetric flask to prepare the aqueous uranium standard solution

[0052] The maximum allowable deviation of a 100mL volumetric flask is ±0.10mL. Considering uniform distribution, its standard uncertainty is

[0053]

[0054] The capacity of the volumetric flask is V = 100 mL, and the volume expansion coefficient of water at 20°C is 2.1×10 -4 / ℃, the laboratory temperature is (20±5)℃, calculated according to normal distribution, taking k=2, the standard uncertainty is

[0055]

[0056] According to the above uncertainty components, the relative uncertainty u introduced by the 100mL volumetric flask is obtained. r (V 100 )for

[0057]

[0058] Relative uncertainty component u generated by stock solution preparation r (V)

[0059]

[0060] (4) Uncertainty component u introduced by sampling volume r (V'):

[0061] Uncertainty introduced by calibration of adjustable 1000 μL pipette, u(V 1000 )

[0062] The uncertainty introduced by the pipette calibration u1(V 1000 ), the maximum allowable error of the adjustable 1000μL pipette capacity is ±0.6%, considering the uniform distribution, then:

[0063]

[0064] The maximum capacity of the autosampler is V = 1000 μL, the calibration temperature is 20 °C, and the expansion coefficient of water is 2.1 × 10 -4 / ℃, the laboratory temperature is (20±5)℃, according to the normal distribution, take k=2, then:

[0065]

[0066] According to the above uncertainty components, we can get:

[0067]

[0068] u r (V') = u rel (V 1000 )=u(V 1000 ) / V 1000 =3.50×10 -3

[0069] (5) Combined standard uncertainty

[0070]

[0071] The relative uncertainty introduced by the preparation of organic phase uranium standard using U3O8 certified reference material is 0.43%.

[0072] Considering that the UO3 reference standard material also needs to be determined by an automatic positioning titrator (refer to the nuclear standard EJ-T20164-2018, RSD is 0.04%), the uncertainty caused by the determination needs to be considered, and the Saybel formula can be obtained:

[0073]

[0074] However, UO3 is not a certified standard and its relative standard uncertainty is

[0075]

[0076] The above data show that the relative uncertainty introduced by the preparation of organic phase uranium standards using U3O8 certified standard materials and the preparation of organic phase uranium working standards using UO3 reference standard materials after automatic positioning titration is 0.43%.

[0077] Compared with the prior art, the present invention has the following beneficial effects:

[0078] (1) The present invention provides a method for constructing an organic phase uranium working curve, which uses 30 vol% TBP-kerosene extraction and accurately controls the extraction acidity, phase ratio and number of times to achieve an excellent uranium separation effect, and achieves complete entry of uranium in the aqueous phase into the organic phase; and the uranium content in the organic phase is determined by combining automatic potentiometric titrator and trace uranium analyzer analysis technology. The method is accurate and reliable as verified by theory and experiment, and improves the accuracy and reliability of the determination of uranium content in the organic phase.

[0079] (2) The relative uncertainty introduced by the preparation of the organic uranium working standard provided by the present invention is 0.43%. This low uncertainty value indicates that the method has high accuracy and stability in the measurement and preparation process, thereby effectively ensuring the recovery and reuse of uranium and reducing environmental pollution. It has important application value for the closed cycle of nuclear fuel and the recycling of uranium resources. DETAILED DESCRIPTION

[0080] The present invention is described in detail below in conjunction with specific embodiments. Any features such as preparation means, materials, structures or composition ratios not clearly described in this technical solution are regarded as common technical features disclosed in the prior art.

[0081] Example 1

[0082] This embodiment provides a method for constructing an organic phase uranium working curve, comprising the following steps:

[0083] S1. Preparation of aqueous uranium standard solution

[0084] 1.486 g of U3O8 certified standard material (GBW 04201, w(U)=(84.754±0.020)%, (k=2)) was weighed and placed in a quartz beaker, 20 mL of 6 mol / L nitric acid was added, and the solution was heated on a hot plate set at 230° C. for the first dissolution. After the solution was completely dissolved, the solution was heated to nearly dryness, and the heating was stopped and evaporated to dryness using the remaining heat, and 20 mL of 6 mol / L nitric acid was added for the second dissolution and cooled to room temperature; the solution was then transferred to a 100 mL volumetric flask, the beaker was repeatedly cleaned three times with 6 mol / L nitric acid as a medium, and the solution was transferred to a volumetric flask, and the solution was fixed to volume with 6 mol / L nitric acid and shaken to obtain an aqueous uranium standard solution with a concentration of 12.595 g / L.

[0085] S2. Preparation of 30 vol% tributyl phosphate-kerosene

[0086] 30 mL of tributyl phosphate was added to 70 mL of kerosene, and the mixture was washed three times with 100 mL of 5 wt% Na2CO3 solution, washed with water until neutral, washed three times with 100 mL of 1 mol / L nitric acid, and washed with water until neutral.

[0087] S3. Preparation of organic phase uranium standard solution

[0088] Use a pipette to transfer 1 mL of aqueous uranium standard into an extraction tube, add 1 mL of 30 vol% tributyl phosphate-kerosene to extract for 5 min, centrifuge for 1 min, take the lower aqueous phase into a sample tube, repeat the above operation, and extract three times in total; then transfer the residual liquid to a 5 mL volumetric flask and dilute to the scale with water; then transfer the organic phase after the three extractions to a 10 mL volumetric flask, use 30 vol% TBP-kerosene as the medium to wash the three extraction tubes in turn for multiple times, transfer them to the volumetric flask together, and make up to volume with 30 vol% TBP-kerosene to obtain an organic phase uranium standard solution.

[0089] S4. Sample determination and analysis

[0090] The concentration of the aqueous uranium standard solution is known to be 12.595 g / L. The uranium concentration of the raffinate is determined by a trace uranium analyzer, and the data is the average of two results.

[0091] To ensure the accuracy of the data, A, B, and C each measured two sets of data, as shown in Table 1. 2+ ] 原液 :[UO2 2 + ] 萃残液 ≥10000:1, it can be considered that all the uranium in the aqueous uranium solution is transferred to the organic phase.

[0092] Table 1 Uranium sample analysis data

[0093]

[0094] S5. The concentration of the organic phase uranium standard solution is calculated using the following formula:

[0095] [UO2 2+ ] 有机相 =[UO2 2+ ] 原液 / n=12.595 / 10=1.300(g / L)

[0096] Where:

[0097] [UO2 2+ ] 有机相 is the concentration of uranium in the organic phase uranium standard solution, grams per liter (g / L);

[0098] [UO2 2+ ] 原液 is the concentration of uranium in the aqueous uranium stock solution, grams per liter (g / L);

[0099] n is the dilution factor, i.e., the factor at which uranium is extracted from the aqueous phase into the organic phase, the organic phase solution is transferred to a volumetric flask, and the volume is fixed to the final volume with 30 vol% TBP-kerosene.

[0100] The organic phase uranium standard solution prepared by S3 was diluted step by step to obtain multiple groups of organic phase uranium standards. The concentrations of the multiple groups of organic phase uranium standards were measured by X-ray fluorescence spectrometer, and the organic phase uranium standard curve was established with the multiple groups of organic phase uranium standard concentrations as the abscissa and the integrated area of ​​light intensity as the ordinate.

[0101] Through the organic phase uranium standard curve, the light intensity of uranium in the organic phase can be directly measured by X-ray fluorescence spectrometer, and then the corresponding organic phase uranium concentration can be obtained.

[0102] Uncertainty assessment is required when establishing the standard curve of organic uranium:

[0103] (1) Relative standard uncertainty u generated by standard reagents r (p):

[0104] The reagent purity of the standard substance U3O8 (GBW04021, National Center for Standard Material Research) used is (84.754±0.02)%, which is converted into standard uncertainty according to uniform distribution:

[0105]

[0106] (2) Relative standard uncertainty u generated by weighing r (m):

[0107] The uncertainty caused by balance calibration, the statutory allowable error for analytical balances that have passed metrological verification is 0.1 mg, which is converted into a standard uncertainty of 0.1 / 1.73=0.058 mg based on uniform distribution; referring to other analytical balances within 20g, the standard uncertainty of sample weight variability is ±0.07 mg.

[0108]

[0109] If the standard mass of U is weighed: 10.000g

[0110]

[0111] (3) Uncertainty component u generated by the preparation of uranium stock solution r (V):

[0112] ① Use a 10mL volumetric flask to prepare the organic phase uranium standard solution

[0113] The maximum allowable deviation of a 10mL volumetric flask is ±0.04mL. Considering uniform distribution, its standard uncertainty is

[0114]

[0115] The volume of the volumetric flask is V = 10 mL, and the volume expansion coefficient of water at 20°C is 2.1×10 -4 / ℃, the laboratory temperature is (20±5)℃, calculated according to normal distribution, taking k=2, the standard uncertainty is

[0116]

[0117] According to the above uncertainty components, the relative uncertainty u introduced by the 10mL volumetric flask is obtained. r (V 10 )for

[0118]

[0119] ② Use a 100mL volumetric flask to prepare the aqueous uranium standard solution

[0120] The maximum allowable deviation of a 100mL volumetric flask is ±0.10mL. Considering uniform distribution, its standard uncertainty is

[0121]

[0122] The capacity of the volumetric flask is V = 100 mL, and the volume expansion coefficient of water at 20°C is 2.1×10 -4 / ℃, the laboratory temperature is (20±5)℃, calculated according to normal distribution, taking k=2, the standard uncertainty is

[0123]

[0124] According to the above uncertainty components, the relative uncertainty u introduced by the 100mL volumetric flask is obtained. r (V 100 )for

[0125]

[0126] Relative uncertainty component u generated by stock solution preparation r (V)

[0127]

[0128] (4) Uncertainty component u introduced by sampling volume r (V'):

[0129] Uncertainty introduced by calibration of adjustable 1000 μL pipette, u(V 1000 )

[0130] The uncertainty introduced by the pipette calibration u1(V1000 ), the maximum allowable error of the adjustable 1000μL pipette capacity is ±0.6%, considering the uniform distribution, then:

[0131]

[0132] The maximum capacity of the autosampler is V = 1000 μL, the calibration temperature is 20 °C, and the expansion coefficient of water is 2.1 × 10 -4 / ℃, the laboratory temperature is (20±5)℃, according to the normal distribution, take k=2, then:

[0133]

[0134] According to the above uncertainty components, we can get:

[0135]

[0136] u r (V') = u rel (V 1000 )=u(V 1000 ) / V 1000 =3.50×10 -3

[0137] (5) Combined standard uncertainty

[0138]

[0139] The relative uncertainty introduced by the preparation of organic phase uranium standard using U3O8 certified reference material is 0.43%.

[0140] Example 2

[0141] S1. Preparation of aqueous uranium solution

[0142] Weigh 1.514g of UO3 reference standard substance and place it in a quartz beaker, add 20mL of 6mol / L nitric acid, heat on a hot plate set at 230℃ for the first dissolution, and after complete dissolution, heat until nearly dry, stop heating and use the remaining heat to evaporate to dryness, add 20mL of 6mol / L nitric acid for the second dissolution and cool to room temperature, then transfer the solution to a 100mL volumetric flask, repeatedly wash the beaker three times with 6mol / L nitric acid as the medium, transfer it to the volumetric flask, make up to volume with 6mol / L nitric acid and shake well to obtain an aqueous uranium solution with a concentration of 12.595g / L.

[0143] S2. Preparation of 30 vol% tributyl phosphate-kerosene

[0144] 30 mL of tributyl phosphate was added to 70 mL of kerosene, and the mixture was washed three times with 100 mL of 5 wt% Na2CO3 solution, washed with water until neutral, washed three times with 100 mL of 1 mol / L nitric acid, and washed with water until neutral.

[0145] S3. Preparation of organic phase uranium standard solution

[0146] Use a pipette to transfer 1 mL of aqueous uranium standard into an extraction tube, add 1 mL of 30 vol% tributyl phosphate-kerosene to extract for 5 min, centrifuge for 1 min, take the lower aqueous phase into a sample tube, repeat the above operation, and extract three times in total; then transfer the residual liquid to a 5 mL volumetric flask and dilute to the scale with water; then transfer the organic phase after the three extractions to a 10 mL volumetric flask, use 30 vol% TBP-kerosene as the medium to wash the three extraction tubes in turn for multiple times, transfer them to the volumetric flask together, and make up to volume with 30 vol% TBP-kerosene to obtain an organic phase uranium standard solution.

[0147] S4. Sample determination and analysis

[0148] The concentration of the aqueous uranium solution was determined to be 12.595 g / L using an automatic potentiometric titrator; the uranium concentration of the raffinate was determined using a trace uranium analyzer, and the data was taken as the average of the two results;

[0149] To ensure the accuracy of the data, A, B, and C each measured two sets of data, as shown in Table 1. 2+ ] 原液 :[UO2 2 + ] 萃残液 ≥10000:1, it can be considered that all the uranium in the aqueous uranium solution is transferred to the organic phase.

[0150] S5. The concentration of the organic phase uranium standard solution is calculated using the following formula:

[0151] [UO2 2+ ] 有机相 =[UO2 2+ ] 原液 / n=12.595 / 10=1.300(g / L)

[0152] Where:

[0153] [UO2 2+ ] 有机相 is the concentration of uranium in the organic phase uranium standard solution, grams per liter (g / L);

[0154] [UO2 2+ ] 原液 is the concentration of uranium in the aqueous uranium stock solution, grams per liter (g / L);

[0155] n is the dilution factor, i.e., the factor at which uranium is extracted from the aqueous phase into the organic phase, the organic phase solution is transferred to a volumetric flask, and the volume is fixed to the final volume with 30 vol% TBP-kerosene.

[0156] The organic phase uranium standard solution prepared by S3 was diluted step by step to obtain multiple groups of organic phase uranium standards. The concentrations of the multiple groups of organic phase uranium standards were measured by X-ray fluorescence spectrometer, and the organic phase uranium standard curve was established with the multiple groups of organic phase uranium standard concentrations as the abscissa and the integrated area of ​​light intensity as the ordinate.

[0157] Through the organic phase uranium standard curve, the light intensity of uranium in the organic phase can be directly measured by X-ray fluorescence spectrometer, and then the corresponding organic phase uranium concentration can be obtained.

[0158] Uncertainty assessment is required when establishing the standard curve of organic uranium:

[0159] (1) Relative standard uncertainty u generated by weighing r (m):

[0160] The uncertainty caused by balance calibration, the statutory allowable error for analytical balances that have passed metrological verification is 0.1 mg, which is converted into a standard uncertainty of 0.1 / 1.73=0.058 mg based on uniform distribution; referring to other analytical balances within 20g, the standard uncertainty of sample weight variability is ±0.07 mg.

[0161]

[0162] If the standard mass of U is weighed: 10.000g

[0163]

[0164] (2) Uncertainty component u generated by the preparation of uranium stock solution r (V):

[0165] ① Use a 10mL volumetric flask to prepare the organic phase uranium standard solution

[0166] The maximum allowable deviation of a 10mL volumetric flask is ±0.04mL. Considering uniform distribution, its standard uncertainty is

[0167]

[0168] The volume of the volumetric flask is V = 10 mL, and the volume expansion coefficient of water at 20°C is 2.1×10 -4 / ℃, the laboratory temperature is (20±5)℃, calculated according to normal distribution, taking k=2, the standard uncertainty is

[0169]

[0170] According to the above uncertainty components, the relative uncertainty u introduced by the 10mL volumetric flask is obtained. r (V 10 )for

[0171]

[0172] ② Use a 100mL volumetric flask to prepare the aqueous uranium standard solution

[0173] The maximum allowable deviation of a 100mL volumetric flask is ±0.10mL. Considering uniform distribution, its standard uncertainty is

[0174]

[0175] The capacity of the volumetric flask is V = 100 mL, and the volume expansion coefficient of water at 20°C is 2.1×10 -4 / ℃, the laboratory temperature is (20±5)℃, calculated according to normal distribution, taking k=2, the standard uncertainty is

[0176]

[0177] According to the above uncertainty components, the relative uncertainty u introduced by the 100mL volumetric flask is obtained. r (V 100 )for

[0178]

[0179] Relative uncertainty component u generated by stock solution preparation r (V)

[0180]

[0181] (3) Uncertainty component u introduced by sampling volume r (V'):

[0182] Uncertainty introduced by calibration of adjustable 1000 μL pipette, u(V 1000 )

[0183] The uncertainty introduced by the pipette calibration u1(V 1000 ), the maximum allowable error of the adjustable 1000μL pipette capacity is ±0.6%, considering the uniform distribution, then:

[0184]

[0185] The maximum capacity of the autosampler is V = 1000 μL, the calibration temperature is 20 °C, and the expansion coefficient of water is 2.1 × 10 -4 / ℃, the laboratory temperature is (20±5)℃, according to the normal distribution, take k=2, then:

[0186]

[0187] According to the above uncertainty components, we can get:

[0188]

[0189] u r (V') = u rel (V 1000 )=u(V 1000 ) / V 1000 =3.50×10 -3

[0190] (4) Combined standard uncertainty

[0191] Considering that the UO3 reference standard material also needs to be determined by an automatic positioning titrator (refer to the nuclear standard EJ-T20164-2018, RSD is 0.04%), the uncertainty caused by the determination needs to be considered, and the Saybel formula can be obtained:

[0192]

[0193] However, UO3 is not a certified standard and its relative standard uncertainty is

[0194]

[0195] The above data show that the relative uncertainty introduced by the preparation of organic phase uranium standards using U3O8 certified standard materials and the preparation of organic phase uranium working standards using UO3 reference standard materials after automatic positioning titration is 0.43%.

[0196] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A method for constructing an organic phase uranium working curve, characterized in that: The following steps are involved: S1. Preparation of aqueous uranium stock solution; S2, preparation of 30 vol% tributyl phosphate-kerosene; S3, using the 30 vol% tributyl phosphate-kerosene prepared in S2 to extract the aqueous uranium stock solution prepared in S1 to prepare an organic uranium standard solution; S4, determining and analyzing the concentration of uranium in the aqueous uranium stock solution prepared in S1 and the raffinate in S3; S5. Calculation of the concentration of organic phase uranium standard solution and establishment of organic phase uranium standard curve.

2. The method for constructing an organic phase uranium working curve according to claim 1, characterized in that: In S1, the preparation of aqueous uranium stock solution comprises: Add 6-8 mol / L nitric acid to the U3O8 certified standard substance or the UO3 reference standard substance, heat for the first dissolution, evaporate to dryness after complete dissolution, add 6-8 mol / L nitric acid for the second dissolution and cool to room temperature, finally transfer the solution to a volumetric flask, make up to volume with 4-6 mol / L nitric acid to obtain an aqueous uranium standard solution or aqueous uranium solution.

3. The method for constructing an organic phase uranium working curve according to claim 2, characterized in that: The U3O8 certified standard material is GBW 04201.

4. The method for constructing an organic phase uranium working curve according to claim 2, characterized in that: The heating temperature is 230-290°C.

5. The method for constructing an organic phase uranium working curve according to claim 1, characterized in that: In S2, the preparation of 30 vol% tributyl phosphate-kerosene comprises: Tributyl phosphate was added to kerosene and washed with 5wt% Na2CO3 solution, water, 1mol / L nitric acid and water in sequence until neutral.

6. The method for constructing an organic phase uranium working curve according to claim 5, characterized in that: The volume ratio of tributyl phosphate to kerosene is 3:

7.

7. The method for constructing an organic phase uranium working curve according to claim 1, characterized in that: In S3, the aqueous uranium stock solution prepared in S1 is extracted with 30 vol% tributyl phosphate-kerosene prepared in S2 to prepare an organic uranium standard solution, comprising: The aqueous uranium stock solution prepared in S1 was extracted with 30 vol% tributyl phosphate-kerosene prepared in S2, the residual solution was transferred to a volumetric flask, diluted to the mark with water, and then the extracted organic phase was transferred to another volumetric flask to make up the volume to obtain an organic uranium standard solution.

8. The method for constructing an organic phase uranium working curve according to claim 7, characterized in that: In S4, the concentration of uranium in the aqueous uranium stock solution prepared in S1 and the raffinate in S3 is determined and analyzed, including: The concentration of the aqueous uranium standard solution is known, and the aqueous uranium solution is determined by an automatic potentiometric titrator, and the concentration of uranium in the raffinate is determined by a trace uranium analyzer.

9. The method for constructing an organic phase uranium working curve according to claim 1, characterized in that: In S5, the concentration of the organic phase uranium standard solution is calculated and the organic phase uranium standard curve is established by the following calculation formula: [UO2 2+ ] 有机相 =[UO2 2+ ] 原液 / n Where: [UO2 2+ ] 有机相 is the concentration of uranium in the organic phase uranium standard solution, grams per liter (g / L); [UO2 2+ ] 原液 is the concentration of uranium in aqueous uranium stock solution, where the aqueous uranium stock solution is an aqueous uranium standard solution or an aqueous uranium solution, in grams per liter (g / L); n is the dilution factor; The organic phase uranium standard solution prepared by S3 was diluted step by step to obtain multiple groups of organic phase uranium standards. The concentrations of the multiple groups of organic phase uranium standards were measured by X-ray fluorescence spectrometer, and the organic phase uranium standard curve was established with the multiple groups of organic phase uranium standard concentrations as the abscissa and the integrated area of ​​light intensity as the ordinate.

10. The method for constructing an organic phase uranium working curve according to claim 1, characterized in that: When establishing the standard curve of organic uranium, uncertainty assessment needs to be performed, including: The relative standard uncertainty u generated by the standard reagent r (p); Relative standard uncertainty u generated by weighing r (m); Uncertainty component u generated by the preparation of uranium stock solution r (V); The uncertainty component u introduced by the sampling volume r (V'); Finally, the combined standard uncertainty is calculated.

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