Method for testing content of americium in high-level liquid waste

Abstract

This invention relates to the field of nuclear fuel analysis technology, and in particular to a method for testing the americium content in high-level radioactive waste liquid, which uses ICP-MS to measure the americium content in the diluted solution of high-level radioactive waste liquid samples. 243 Am content; the high-level radioactive waste liquid sample dilution was treated with extraction column chromatography and then measured using thermal ionization mass spectrometry. 241 Am and 243 Am isotope abundance ratio; according to 243 The test results of Am content and 241 Am and 243 Am isotope abundance ratio, calculation 241 The americium content is obtained by measuring the am content. This method can not only test the americium content in the diluted solution of high-level radioactive waste samples with an accuracy of 3.8-4.5%, but also utilizes plutonium isotope correction during the thermal ionization mass spectrometry measurement process. 241 Pu 241 The effect of Am significantly improves the accuracy of americium content testing; in addition, the detection limit of this method can reach 0.0003 ng / mL, which can meet the application requirements and has broad application prospects.

Description

Technical Field

[0001] This invention relates to the field of nuclear fuel analysis technology, and in particular to a method for testing the americium content in high-level radioactive waste. Background Technology

[0002] Americium, an important alpha nuclide, is found in high-level radioactive waste. Its two isotopes... 241 Am and 243 Ammonium (Am) has attracted much attention due to its long half-life and high utilization value, making the analysis of Am content in high-level radioactive waste liquid of great significance.

[0003] High-level radioactive waste liquids have a highly complex chemical composition, containing a wide variety of fission products and numerous impurity elements. Measuring am requires consideration of separating the matrix from impurities and removing interference from other actinide elements, especially plutonium. Furthermore, due to the high radioactivity and toxicity of high-level radioactive waste liquids, samples must be processed in a small laboratory. However, sample handling in a small laboratory requires the use of robotic arms, and the complex environment, especially with numerous pretreatment steps, makes operation difficult. Therefore, high-level radioactive waste liquids are typically diluted to an intermediate-level radioactivity level before being transferred to an intermediate-level laboratory for measurement. However, the am content in diluted samples is relatively low, necessitating the selection of appropriate pretreatment methods and measurement techniques.

[0004] Currently, the main analytical methods for americium content both domestically and internationally include ion exchange chromatography, extraction, and extraction column chromatography. For example, some reports have described using anion exchange columns containing quaternary ammonium salts to remove plutonium interference, or using TRPO-xylene to separate americium and other α-nuclides from strong γ-nuclides such as cesium, followed by back-extraction of americium under high acid conditions to separate it from other α-nuclides, thus allowing for americium content measurement. TRPO-xylene, as a classic extractant, offers advantages such as speed, simplicity, and good selectivity in the extraction of transuranic nuclides from radioactive solutions. However, the main drawback of this method is the generation of radioactive organic waste during separation, which is detrimental to environmentally friendly development, and solvent extraction is difficult to automate. Ion exchange, on the other hand, utilizes the different binding abilities of exchangeable groups in ion exchangers with various ions in solution for separation. It is commonly used to separate and purify Pu, Np, and Am, and is often used in the form of chromatographic columns. However, the selectivity coefficient of Am(III) in anion exchange resins is generally low, while anion exchange resins show better selectivity for Pu and Np. Therefore, ion exchange is a widely used separation technology due to its wide applicability, simple operation, and low cost. However, compared to solvent extraction, its selectivity is generally poor.

[0005] In view of this, the present invention is proposed. Summary of the Invention

[0006] The purpose of this invention is to provide a method for testing the americium content in high-level radioactive waste liquid. This method can not only test the americium content in the diluted solution of high-level radioactive waste liquid samples with an accuracy of 3.8-4.5%, but also proposes the use of plutonium isotope correction during the thermal ionization mass spectrometry measurement process. 241 Pu 241 The effect of Am significantly improves the accuracy of americium content testing.

[0007] This invention provides a method for testing the americium content in high-level radioactive waste liquid, comprising the following steps:

[0008] S1. ICP-MS was used to directly measure the concentration of high-level radioactive waste liquid in the diluted solution. 243 Am content;

[0009] S2. The diluted high-level radioactive waste liquid sample was processed by extraction column chromatography and then measured using thermal ionization mass spectrometry. 241 Am and 243 Am isotope abundance ratio;

[0010] S3, according to 243 The test results of Am content and 241 Am and 243 Am isotope abundance ratio, calculation 241 The content of Am is used to obtain the content of americium;

[0011] There is no restriction on the order of steps S1 and S2.

[0012] As a preferred embodiment of this technical solution, in step S1, the first step is to prepare... 241 Am series standard solutions, 243 The mass concentration of Am in the standard solution was obtained by thermal ionization mass spectrometry. 241 Am and 243 The abundance ratio of Am isotopes was calculated, thus establishing the ICP-MS measurement method. 243 Methods for determining Am content.

[0013] Because it is not available on the market 243 Am standard product, and 241 Am standard contains some 243 Am, therefore, can be prepared 241 Am series standard solutions, and the standard solutions obtained by thermal ionization mass spectrometry. 241 Am and 243 Am isotope abundance ratio, calculation 243 The mass concentration of Am was determined, and an ICP-MS measurement method was established based on this. 243 Methods for determining Am content.

[0014] As a preferred embodiment of this technical solution, in step S2, during the extraction column chromatography process, a DGA resin column is first used to purify and separate the sample to be tested in order to remove the interference of trivalent actinides on the detection results, and then a TEVA resin column is used to purify and separate the sample to be tested in order to remove the influence of plutonium.

[0015] As a preferred embodiment of this technical solution, before purifying and separating the sample to be tested using DGA resin, the high-level radioactive waste sample diluent is heated and concentrated to near dryness, and then first nitric acid is added for conversion, so as to completely replace the solvent in the high-level radioactive waste sample diluent with first nitric acid. The volume of first nitric acid required for every 100 μg of americium in the high-level radioactive waste sample diluent is 1-2 mL, and the concentration of first nitric acid is 7.5 mol / L, so as to fully dissolve the high-level radioactive waste sample.

[0016] In a preferred embodiment of this technical solution, when purifying and separating the sample to be tested using a DGA resin column, the high-level radioactive waste sample solution after conversion is transferred to a pre-equilibrated DGA resin column. The beaker is washed 2-3 times with first nitric acid, and the washing solution is transferred into the DGA resin column together with the washing solution. Then, first nitric acid is used as the eluent to wash the trivalent actinide impurities. Finally, americium is eluted with hydrochloric acid, and the eluent is collected. The concentration of hydrochloric acid is 0.1-0.2 mol / L.

[0017] In a preferred embodiment of this technical solution, before purifying and separating the sample using a TEVA resin column, the eluent is heated and concentrated to near dryness, dissolved using second nitric acid, and then ferrous aminosulfonate solution is added to adjust the valence for 3-8 minutes. Sodium nitrite solution is then added, and the mixture is shaken until no bubbles are present to reduce the high-valence americium to stable trivalent americium and adjust the plutonium to tetravalent, thus obtaining a sample solution with adjusted valence. The volumes of second nitric acid, ferrous aminosulfonate solution, and sodium nitrite solution required per 100 μg of americium in the high-level radioactive waste sample dilution are preferably 0.5-1.5 mL, 0.1-0.2 mL, and 0.1-0.2 mL, respectively. The concentration of second nitric acid is 3-5 mol / L, the concentration of ferrous aminosulfonate solution is 0.1-0.3 mol / L, and the concentration of sodium nitrite solution is 1-3 mol / L.

[0018] In a preferred embodiment of this technical solution, when using a TEVA resin column to purify and separate the sample to be tested, the valence-adjusted sample solution is transferred to a pre-equilibrated TEVA resin column, and nitric acid is used as the eluent to collect the americium-containing measurement solution. The americium-containing measurement solution is then concentrated by heating to obtain an americium-containing concentrate. The concentration of nitric acid is 5 mol / L. In this nitric acid medium, TEVA resin has excellent adsorption performance for tetravalent plutonium but poor adsorption capacity for trivalent americium.

[0019] As a preferred embodiment of this technical solution, before using a thermal ionization mass spectrometer for measurement, the sample band is installed on the spotter, the spotter current is adjusted to 0.5A, 2-5μL of americium-containing concentrate is dropped into the center of the sample band in 3-5 portions, and after the sample is completely evaporated, the current is rapidly increased to 1.8A and maintained for 10s, and then the current is reduced to 0A.

[0020] As a preferred embodiment of this technical solution, when using a thermal ionization mass spectrometer for measurement, the sample band is loaded onto a sample tray, the sample tray is transferred into the ion source, and the measurement is performed when the vacuum degree is <10. -5 Pa, vacuum level in the analysis chamber <10 -6 After pa, within 10 min, the sample band and ionization band were raised to 1.5 A and 4.5 A respectively, and the instrument focusing parameters were adjusted to... 241 Am ion current signal maintained at 10 -11 At approximately A, the total evaporation measurement begins until the sample is completely evaporated. The instrument automatically records the ion current intensity at mass numbers 241 and 243 and calculates the abundance ratio.

[0021] As a preferred embodiment of this technical solution, the isotopic abundance of plutonium is monitored during the thermal ionization mass spectrometry measurement process to correct for... 241 Pu 241 The effect of Am.

[0022] In the sample to be tested 239 Pu and 241 The isotopic abundance ratio of Pu is determined, and... 239 The PU content is much higher than 241 Therefore, during the thermal ionization mass spectrometry measurement process, it is possible to monitor... 239 The content of Pu was used to preliminarily determine the separation effect of plutonium-americium. When 239 A high Pu content indicates incomplete sample pretreatment; when 239 A very low Pu content indicates good plutonium-americium separation. 241 Pu 241 Am's contribution is essentially negligible; when 239 When the Pu content is in the middle range, it can be corrected by plutonium isotope abundance. 241 Pu 241 The effect of Am.

[0023] The method for testing the americium content in high-level radioactive waste liquid of the present invention has at least the following technical advantages:

[0024] This invention uses ICP-MS for determination. 243 The Am content was then purified and separated using DGA and TEVA resin columns, and determined by thermal ionization mass spectrometry. 241 Am and 243 Am isotope ratios, obtained241 The americium content is obtained by measuring the am content, thereby determining the total americium content. This method can not only test the americium content in the diluted solution of high-level radioactive waste samples with an accuracy of 3.8-4.5%, but also proposes the use of plutonium isotope correction during the thermal ionization mass spectrometry measurement process. 241 Pu 241 The influence of Am significantly improves the accuracy of americium content testing; at the same time, studies have shown that the detection limit of this method can reach 0.0003 ng / mL, which can fully meet the needs of practical use and has broad application prospects. Detailed Implementation

[0025] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0026] It should be noted that the terminology used herein is for the purpose of describing particular implementations only and is not intended to limit the exemplary implementations according to this application. As used herein, the singular form includes the plural form unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this description, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0027] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] Example 1

[0029] S1, First prepare 241 Am series standard solutions, 243 The mass concentration of Am in the standard solution was obtained by thermal ionization mass spectrometry. 241 Am and 243 The abundance ratio of Am isotopes was calculated, thus establishing the ICP-MS measurement method. 243 The method for determining Am content involves measuring it using the established ICP-MS method. 243 The method for measuring Am content is to directly measure the Am content in the diluted solution of high-level radioactive waste samples. 243 Am content;

[0030] S2. The diluted high-level radioactive waste liquid sample was processed by extraction column chromatography and then measured using thermal ionization mass spectrometry. 241 Am and 243The isotopic abundance ratio of Am includes the following steps;

[0031] a. Equilibrium of DGA resin column

[0032] Soak the DGA resin in deionized water for 24 hours, then soak it in 7.5 mol / L nitric acid for 2 hours. Wash it with deionized water until neutral, and then pack it into a glass column with an inner diameter of 10 mm using a wet method. After packing, the column should be free of gaps, breaks, and air bubbles. The resin bed height should be 160 mm, and the flow rate should be controlled at 0.8-1.2 mL / min.

[0033] b. Sample loading onto column

[0034] The DGA resin column was pre-equilibrated with 20-25 mL of 7.5 mol / L nitric acid.

[0035] Accurately transfer a certain volume (containing approximately 100 μg of americium) of the high-level radioactive waste sample dilution into a 50-100 mL beaker. Place the beaker on a hot plate and heat it to near dryness at 100-120 °C. Add 1 mL of 7.5 mol / L nitric acid to the beaker and transfer the solution to a pre-equilibrated DGA resin column. Wash the beaker 2-3 times with a small amount of 7.5 mol / L nitric acid, and transfer the washing solution into the DGA resin column. Then, use 15 mL of 7.5 mol / L nitric acid as the eluent to elute the impurity elements. Finally, elute the americium with 0.2 mol / L hydrochloric acid and collect 45 mL of the eluent.

[0036] The eluent was concentrated by heating it on a hot plate at a temperature of 100-120°C. The americium-containing eluent was concentrated to near dryness and set aside.

[0037] c. Sample price adjustment

[0038] Dissolve the americium-containing sample in 1 mL of 4 mol / L nitric acid, add 0.1 mL of 0.2 mol / L ferrous aminosulfonate solution to adjust the valence for 5 min, then add 0.1 mL of 2 mol / L sodium nitrite solution and shake until no bubbles are generated.

[0039] d. Equilibrium of TEVA resin column

[0040] The flow rate of the TEVA resin column was 0.8-1.2 mL / min. The column was first rinsed with 10 mL of deionized water, and then rinsed with 10 mL of 5 mol / L HNO3 solution to equilibrate the TEVA resin column.

[0041] e. Separation of TEVA resin columns

[0042] The calibrated sample solution was transferred to a pre-equilibrated TEVA resin column. The TEVA resin column was rinsed with 12 mL of 5 mol / L HNO3, and the americium content measurement solution was collected. The americium content measurement solution was concentrated by heating on a hot plate at a temperature of 100-120℃ until it was reduced to 0.1 mL, thus obtaining the americium concentration solution for later use.

[0043] f. Sample preparation and measurement

[0044] Install the sample strip onto the spotter, adjust the spotter current to 0.5A, take 5μL of americium concentrate and drop it onto the center of the sample strip in 3 portions. After the sample is completely evaporated, the current is rapidly increased to 1.8A and held for 10s, then the current is reduced to 0A.

[0045] Load the sample strip onto the sample tray, then transfer the sample tray into the ion source and wait until the vacuum level is <10. -5 Pa, vacuum level in the analysis chamber <10 -6 After pa, within 10 min, the sample band and ionization band were raised to 1.5 A and 4.5 A respectively, and the instrument focusing parameters were adjusted to... 241 Am ion current signal maintained at 10 -11 At approximately A, the total evaporation measurement begins until the sample is completely evaporated. The instrument automatically records the ion current intensities at mass numbers 241 and 243 and calculates the abundance ratio.

[0046] S3, according to 243 The test results of Am content and 241 Am and 243 Am isotope abundance ratio, calculation 241 The content of Am is used to obtain the content of americium;

[0047] The test solution was measured five times consecutively using the above method to determine the precision of the method. The test results are shown in Table 1.

[0048] Table 1. Measurement results of combined thermal ionization mass spectrometry and ICP-MS

[0049]

[0050] As shown in Table 1, the precision of this method is 3.8%, and the repeatability of the measurement results is good, ensuring the accuracy of the measurement results.

[0051] In addition, measurements were taken using a thermal ionization mass spectrometer. 241 Am and 243 When calculating the isotopic abundance ratio of Am, the isotopic abundance of plutonium was simultaneously detected and monitored, and the results were corrected using the plutonium isotopic abundance. 241 Pu 241 The effects of Am, and the measured americium content are shown in Table 2.

[0052] Table 2 ICP-MS Measurement Calibration 241 Am results

[0053]

[0054] Table 2 shows that, after plutonium isotope abundance correction 241 Pu 241 After considering the influence of Am, the precision of the americium content measurement in this invention is 4.5%.

[0055] Meanwhile, the detection limit of this method was calculated by adding the average of seven blank measurements to three times the standard deviation of the measurement and dividing by the relative sensitivity. The measurement results are shown in Table 3.

[0056] Table 3. Detection limit measurement results of this method

[0057]

[0058] As shown in Table 3, the detection limit of this method can reach 0.0003 ng / mL, which can fully meet the needs of practical use.

[0059] Compare with Example 1

[0060] TRPO-xylene was used to separate americium and other α-nuclides from strong γ-nuclides such as cesium. Then, americium was back-extracted under high-acid conditions to separate it from other α-nuclides, thus allowing for the measurement of americium content. The specific method is as follows:

[0061] When extracting with TRPO-xylene extractant, the ratio is 1:1 and the extraction time is 5 minutes. After extraction, the organic phase is back-extracted with 6 mol / L nitric acid at a ratio of 1:1 for 10 minutes, and the aqueous phase is used for measurement.

[0062] Everything else is basically the same as in Example 1.

[0063] Methodologically validated, this method has a precision of 10%.

[0064] In summary, compared to Control Example 1, this method not only enables the determination of americium content in the diluted solution of high-level radioactive waste samples with an accuracy of 3.8-4.5%, but also proposes the use of plutonium isotope correction during the thermal ionization mass spectrometry measurement process. 241 Pu 241 The influence of Am significantly improves the accuracy of americium content testing; at the same time, studies have shown that the detection limit of this method can reach 0.0003 ng / mL, which can fully meet the needs of practical use and has broad application prospects.

[0065] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for testing the americium content in high-level radioactive waste liquid, characterized in that, Includes the following steps: S1. ICP-MS was used to directly measure the concentration of high-level radioactive waste liquid in the diluted solution. 243 Am content; S2. The diluted high-level radioactive waste liquid sample was processed by extraction column chromatography and then measured using thermal ionization mass spectrometry. 241 Am and 243 The isotopic abundance ratio of Am was determined, and the isotopic abundance of plutonium was monitored during thermal ionization mass spectrometry measurements to correct for [further details needed]. 241 Pu 241 The impact of Am; S3, according to 243 The test results of Am content and 241 Am and 243 Am isotope abundance ratio, calculation 241 The content of Am is used to obtain the content of americium; In step S1, first prepare 241 Am series standard solutions, 243 The mass concentration of Am in the standard solution was obtained by thermal ionization mass spectrometry. 241 Am and 243 The abundance ratio of Am isotopes was calculated, thus establishing the ICP-MS measurement method. 243 Methods for determining Am content; In step S2, during the extraction column chromatography process, the sample to be tested is purified and separated sequentially using a DGA resin column and a TEVA resin column. There is no restriction on the order of steps S1 and S2.

2. The method for testing the americium content in high-level radioactive waste liquid according to claim 1, characterized in that, Before purifying and separating the test sample using a DGA resin column, the high-level radioactive waste sample dilution was concentrated to near dryness by heating, and then converted by adding primary nitric acid. The volume of the first nitric acid required for every 100 μg of americium in the high-level radioactive waste sample dilution is 1-2 mL, and the concentration of the first nitric acid is 7.5 mol / L.

3. The method for testing the americium content in high-level radioactive waste liquid according to claim 2, characterized in that, When purifying and separating the sample using a DGA resin column, the converted high-level radioactive waste solution is transferred to a pre-equilibrated DGA resin column. The beaker is washed 2-3 times with primary nitric acid, and the washings are transferred to the DGA resin column along with the beaker. Primary nitric acid is then used as the eluent to wash away impurities. Finally, americium is eluted with hydrochloric acid, and the eluent is collected. The concentration of hydrochloric acid is 0.1-0.2 mol / L.

4. The method for testing the americium content in high-level radioactive waste liquid according to claim 3, characterized in that, Before purifying and separating the sample using a TEVA resin column, the eluent was concentrated to near dryness by heating, dissolved in nitric acid, and then ferrous aminosulfonate solution was added to adjust the titration for 3-8 minutes. Sodium nitrite solution was then added, and the mixture was shaken until no bubbles remained, yielding the titrated sample solution. The volumes of secondary nitric acid, ferrous aminosulfonate solution, and sodium nitrite solution required per 100 μg of americium in the high-level radioactive waste sample dilution are 0.5-1.5 mL, 0.1-0.2 mL, and 0.1-0.2 mL, respectively. The concentration of secondary nitric acid is 3-5 mol / L, the concentration of ferrous aminosulfonate solution is 0.1-0.3 mol / L, and the concentration of sodium nitrite solution is 1-3 mol / L.

5. The method for testing the americium content in high-level radioactive waste liquid according to claim 4, characterized in that, When purifying and separating the sample to be tested using a TEVA resin column, the valence-adjusted sample solution is transferred to a pre-equilibrated TEVA resin column, and third nitric acid is used as the eluent to collect the americium-containing measurement solution. The americium-containing measurement solution is then concentrated by heating to obtain an americium-containing concentrate, wherein the concentration of third nitric acid is 5 mol / L.

6. The method for testing the americium content in high-level radioactive waste liquid according to claim 5, characterized in that, Before using thermal ionization mass spectrometry, the sample band is mounted on the spotter, the spotter current is adjusted to 0.5A, 2-5μL of americium-containing concentrate is dropped into the center of the sample band in 3-5 portions, and after the sample is completely evaporated, the current is rapidly increased to 1.8A and held for 10s, and then the current is reduced to 0A.

7. The method for testing the americium content in high-level radioactive waste liquid according to claim 6, characterized in that, When performing measurements using a thermal ionization mass spectrometer, the sample band is loaded onto the sample tray, the sample tray is transferred into the ion source, and the measurement is performed until the vacuum degree is <10. -5 Pa, vacuum level in the analysis chamber <10 -6 After pa, within 10 min, the sample band and ionization band were raised to 1.5 A and 4.5 A respectively, and the instrument focusing parameters were adjusted to... 241 Am ion current signal maintained at 10 -11 At approximately A, the total evaporation measurement begins until the sample is completely evaporated. The instrument automatically records the ion current intensity at mass numbers 241 and 243 and calculates the abundance ratio.

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