Combined analysis method for iodine-plutonium-uranium radioisotope in coral sample

Abstract

The invention discloses a combined analysis method for iodine-plutonium-uranium radioisotope in a coral sample, and belongs to the field of analytical chemistry technology and environmental geochemistry. The method comprises the following steps: infiltrating a coral sample, adding 125I and 242Pu tracers, uniformly mixing, and treating to obtain a pretreated sample solution; the contents of 127I and 238U are measured; adding a 127I carrier and a reducing agent into the pretreated sample solution, and performing extraction and back extraction under an acidic condition to respectively obtain a first water phase solution and a second water phase solution; carrying out precipitation reaction on the second water phase solution to obtain a precipitate, and preparing the precipitate into a target sample to measure the content of 129I; separating and purifying the first water phase solution to obtain a plutonium effluent, eluting to obtain a plutonium eluent, and measuring the contents of 239Pu and 240Pu; and purifying and eluting the plutonium effluent to obtain uranium eluent, and measuring the content of 236U. According to the method, iodine, plutonium and uranium are subjected to joint analysis by using one coral sample, so that the use amount of the coral sample is reduced.

Description

Technical Field

[0001] The invention relates to the fields of analytical chemistry technology and environmental geochemistry, and more specifically to a method for joint analysis of iodine-plutonium-uranium radioactive isotopes in coral samples. Background Art

[0002] Human nuclear activities have produced a large amount of radioactive pollutants that have entered the marine environment. In order to monitor the level of marine radioactivity and its impact on human life and health, studying the content of radionuclides in marine organisms is one of the important means.

[0003] Coral reefs are one of the marine ecosystems that are home to a variety of organisms. They provide living space and food for many marine organisms, as well as many material products and aesthetic values ​​for humans. Coral reefs are distributed several meters deep in the ocean, and their carbonate skeletons retain the composition information of surface seawater and environmental history. Therefore, by measuring the content of radionuclides in coral samples, it is possible to reconstruct the record of the impact of human nuclear activities on the marine environment, trace the circulation process of ocean surface currents, and provide scientific support for the assessment of marine radioactivity levels for the construction of offshore nuclear power plants.

[0004] Iodine-129( 129 I), plutonium-239( 239 Pu), plutonium-240 ( 240 Pu) and uranium-236 ( 236 U) is an important long-lived artificial radionuclide in the marine environment, and is of great significance in the research fields of indicating human nuclear activities and marine environmental tracing. Iodine is an important nutrient element, and the geochemical behavior of iodine is closely related to human health. Therefore, the study of the distribution, source and circulation of iodine in the environment is very important. With the development of nuclear energy, a large amount of radioactive iodine is produced in the nuclear fission process, among which the long-lived iodine-129 with a half-life of 15.7 million years has a high fission yield. Although most of the iodine-129 produced by nuclear reactors is enclosed in the nuclear fuel cladding, it is released into the environment due to nuclear accidents, damage to nuclear fuel assemblies, storage and transportation of spent fuel, and nuclear fuel reprocessing. Iodine-129 has environmental characteristics such as volatility and high chemical activity, and is also an ideal tracer in the study of environmental processes in fields such as marine science and atmospheric science.

[0005] There are three main sources of plutonium in the environment: atmospheric nuclear tests, nuclear facility emissions, and nuclear accidents. Among them, atmospheric nuclear tests are the largest source of plutonium in the environment. In the nuclear reaction that produces plutonium, the first thing produced is plutonium-239, which captures neutrons to produce plutonium-240. That is, the longer the nuclear reaction time, the more plutonium-240 is produced. So generally speaking, more plutonium-240 is produced in nuclear reactors. 240 Pu / 239 Pu ratio is larger, otherwise240 Pu / 239 In addition, due to the different types of reactors and nuclear fuel exposure time, different nuclear weapons have different types and equivalents, which will produce different 240 Pu / 239 Pu ratio. Therefore, we can 240 Pu / 239 The different atomic ratios of Pu are used to identify the source of plutonium in the environment and to trace the type of human nuclear activities and their impact on marine radiation levels.

[0006] Uranium isotopes are conservative elements in the ocean and can migrate with ocean currents. Therefore, uranium-236 can be used as an ocean tracer. It can not only be used for ocean current circulation tracer research, but also obtain information such as the source and input history of this nuclide in the ocean to indicate the impact of human nuclear activities on the marine environment. With the development of mass spectrometers and the continuous improvement of analysis processes in recent years, 236 U has been increasingly reported. For example, in Caribbean coral samples 236 The analysis results of U show that atmospheric nuclear weapons testing causes 236 U reached its environmental peak level in the early 1960s.

[0007] Coral is an ideal medium for recording the marine environment and an important archive for studying human nuclear activities. In order to obtain time series records of the impact of human nuclear activities on the marine environment, coral samples with annual resolution are required. However, the content of radionuclides in coral samples is extremely low. To obtain the content and ratio information of three nuclides, at least dozens of grams of samples are required to meet actual measurement requirements. Coral samples are very precious, and it is usually difficult to obtain a large number of samples with annual resolution, which seriously hinders the use of corals to reconstruct the environmental impact of human nuclear activities and marine environmental tracing applications. Summary of the invention

[0008] In view of the above problems, the present invention provides a method for the joint analysis of iodine-plutonium-uranium radioisotopes in coral samples, which realizes the joint analysis of iodine, plutonium and uranium using a coral sample. The method adopts a highly sensitive accelerator mass spectrometer and inductively coupled plasma mass measurement, which not only reduces the amount of coral samples used from dozens of grams to a few grams, but also can simultaneously measure 127 I. 129 I. 236 U. 238 U. 239 Pu and 240 The Pu content, and 129 I / 127 I. 236 U / 238 U. 240 Pu / 239The isotope ratio of Pu can be widely used in radioactive isotope tracing studies in the marine environment.

[0009] The object of the present invention is to provide a method for the combined analysis of iodine-plutonium-uranium radioisotopes in coral samples, comprising the following steps:

[0010] After the coral sample is soaked, add 125 I tracer and 242 Pu tracer, after being mixed evenly, was acid dissolved, and then the organic matter was removed to obtain the pre-treated sample solution; the pre-treated sample solution was determined by inductively coupled plasma mass spectrometry to obtain the 127 I and 238 U content;

[0011] Add to the pre-treated sample solution 127 I carrier and reducing agent, adding oxidant under acidic conditions to extract the first aqueous phase solution and carbon tetrachloride phase solution; back-extracting the carbon tetrachloride phase solution to obtain a second aqueous phase solution;

[0012] The second aqueous phase solution is subjected to precipitation reaction to obtain a precipitate, and the precipitate is made into a target sample, and the target sample is measured by accelerator mass spectrometry to obtain the content of the coral sample. 129 I content;

[0013] The first aqueous phase solution is subjected to precipitation separation and chromatographic purification to obtain a plutonium effluent, which is then eluted to obtain a plutonium eluate; NH3-He is selected as the collision / reaction gas, and the plutonium eluate is measured in series with APEX and inductively coupled plasma mass spectrometry to obtain the plutonium in the coral sample. 239 Pu and 240 Pu content;

[0014] The plutonium effluent was purified by chromatography, and the uranium eluate was obtained after elution. CO2-He was selected as the collision / reaction gas, and the uranium eluate was measured by APEX and ICP-MS in series to obtain the content of uranium in the coral sample. 236 U content.

[0015] In a preferred embodiment of the present invention, the step of removing organic matter is: adding potassium persulfate to the sample after acid dissolution, and refluxing at 60-70° C. to remove the organic matter.

[0016] In a preferred embodiment of the present invention, the precipitation reaction method is: a reducing agent is added to the second aqueous phase solution, the pH is adjusted to less than 2, and then silver nitrate is added to form a precipitate.

[0017] In a preferred embodiment of the present invention, the precipitation separation method is: adding a compound containing trivalent iron to the first aqueous phase solution, adjusting the pH to 8-9, and separating to obtain a precipitate.

[0018] In a preferred embodiment of the present invention, the chromatographic purification method is: after the precipitate is dissolved and oxidized, it is purified using TEVA extraction chromatography resin to separate and obtain an effluent.

[0019] In a preferred embodiment of the present invention, the elution treatment is to use a mixed solution of hydroxylamine hydrochloride and hydrochloric acid to reduce the plutonium adsorbed on the TEVA extraction chromatography resin to obtain a plutonium eluate.

[0020] In a preferred embodiment of the present invention, the plutonium effluent is subjected to chromatographic purification of uranium using UTEVA resin.

[0021] In a preferred embodiment of the present invention, 127 The content of I was determined by diluting the pretreated sample solution with NH3·H2O. 133 Cs standard solution was used as the internal standard and the content of 127 I concentration, calculated in the sample 127 I content.

[0022] In a preferred embodiment of the present invention, 238 The content of U was determined by diluting the sample solution with nitric acid and then using inductively coupled plasma mass spectrometry to determine the content of U in the solution. 238 U concentration, calculated in the sample 238 U content.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The present invention utilizes the different chemical properties of radioactive isotopes and adopts acid dissolution, solvent extraction, iron hydroxide co-precipitation, and extraction chromatography separation technology to successively separate iodine, plutonium, and uranium isotopes from corals, thereby establishing for the first time a method for separating iodine, plutonium, and uranium isotopes from corals. 127,129 I- 239,240 Pu- 236,238 The combined analysis process of U, each step of separation of elements does not interfere with each other, and the analysis of three radioactive elements (6 nuclides) is achieved using one sample, and the amount of coral sample required can be reduced by at least 10 times compared with the single analysis. The present invention designs a sample analysis process, uses an isotope tracer to monitor the recovery rate of the combined analysis process, separates iodine through extraction enrichment, and separates plutonium and uranium through chromatographic resin, so as to achieve a high recovery rate of iodine, plutonium and uranium isotopes, and the recovery rate can reach 63-98%. An accelerator mass spectrometer and an inductively coupled plasma mass spectrometer are used for high-sensitivity determination, and the method is used for the analysis and research of radionuclides in Wenchang coral samples in my country.

[0025] The method of the invention is not only applicable to the determination of coral samples, but also can be used for the joint analysis of iodine-plutonium-uranium radioactive isotopes in biological carbonate samples. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a flow chart of the combined analysis of iodine-plutonium-uranium radioactive isotopes in coral samples provided by the present invention. DETAILED DESCRIPTION

[0027] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] The content of radionuclides in coral samples is extremely low. To obtain the content and isotope ratio information of the nuclides, at least dozens of grams of samples are needed to meet the actual measurement. However, coral samples are very precious, and it is usually difficult to obtain a large number of samples with annual resolution, which seriously hinders the use of corals to reconstruct the environmental impact of human nuclear activities and marine environmental tracing applications.

[0029] Based on this, the present invention provides a method for the combined analysis of iodine-plutonium-uranium radioisotopes in coral samples. The specific technical solution is as follows:

[0030] A method for combined analysis of iodine-plutonium-uranium radioisotopes in coral samples comprises the following steps:

[0031] The coral samples were soaked in water and then added 125 I tracer and 242 The Pu tracer is mixed evenly, dissolved with acid, and then the organic matter is removed to obtain a pre-treated sample solution; 125 The addition of I tracer was used to calculate iodine recovery during acid dissolution and organic matter digestion.

[0032] Inductively coupled plasma mass spectrometry (ICP-MS) was used to determine the pre-treated sample solution to obtain the content of 127 I and 238 U content;

[0033] Add to the pre-treated sample solution 127 After the carrier and the reducing agent are uniformly mixed, an oxidant is added under acidic conditions to extract the first aqueous phase solution and the carbon tetrachloride phase solution; the carbon tetrachloride phase solution is back-extracted to obtain a second aqueous phase solution; in this step, the solid sample is dissolved by an acid step to form a liquid, and the elements in the sample are all ionized, and then iodine is enriched and purified by extraction and back-extraction, so that all iodine in the sample is enriched in the second aqueous phase solution;

[0034] The second aqueous solution is subjected to precipitation reaction to obtain a precipitate, which is used to prepare a target sample. The target sample is measured by accelerator mass spectrometry (AMS) to obtain the content of the coral sample. 129 I / 127 I atomic ratio, measured by the above coral 127 I content, calculated 129 I content;

[0035] The high-valent plutonium in the first aqueous phase solution is reduced to +3-valent plutonium, and then the pH is adjusted, and iron hydroxide precipitation separation and chromatography purification are performed to separate the plutonium effluent, which is then eluted to obtain the plutonium eluate; NH3-He is selected as the collision / reaction gas, and APEX and ICP-MS are connected in series to determine the plutonium eluate to obtain the plutonium in the coral sample. 239 Pu and 240 Pu content;

[0036] The plutonium effluent was purified by chromatography to obtain uranium eluate. CO2-He was selected as the collision / reaction gas. APEX and ICP-MS were connected in series to obtain the uranium in the coral sample. 236 U content.

[0037] The present invention uses a coral sample to separate iodine, plutonium and uranium isotopes from the coral by using the different chemical properties of radioactive isotopes through acid dissolution, solvent extraction and chromatographic separation technology, and then establishes a method for separating iodine, plutonium and uranium isotopes from the coral sample. 129 I. 239 Pu, 240 Pu and 236 The present invention realizes the analysis of three radioactive elements through one coral sample, thereby reducing the usage of coral samples.

[0038] In a further preferred embodiment of the present invention, the step of removing organic matter is: adding potassium persulfate to the acid-dissolved sample, and refluxing at 60-70° C. to remove the organic matter. It is understandable that the reflux temperature can be 60° C., 61° C., 62° C., 63° C., 64° C., 65° C., 66° C., 67° C., 68° C., 69° C., 70° C., etc., but is not limited to the listed values, and other values ​​not listed within the above numerical range are also applicable.

[0039] In a further preferred embodiment of the present invention, a reducing agent is added to the second aqueous phase solution to adjust the pH to less than 2, and then 0.5 mL of 1 mol / L silver nitrate is added to form an AgI coprecipitate;

[0040] In a further preferred embodiment of the present invention, the precipitate and the niobium powder are mixed in a mass ratio of 1:5 and then pressed into a target sample by a pneumatic press;

[0041] In a further preferred embodiment of the present invention, the precipitation separation method is: adding a compound containing trivalent iron to the first aqueous phase solution, adjusting the pH to 8-9, and separating to obtain a precipitate.

[0042] In a further preferred embodiment of the present invention, the purification method is as follows: after the precipitate is reduced by dissolving sodium bisulfite in hydrochloric acid with a concentration of 12 mol / L, nitric acid with a concentration of 8 mol / L is added to prepare a 3 mol / L nitric acid matrix upper column liquid system, and then TEVA extraction chromatography resin is used to separate and purify plutonium. In this step, the +4 valent plutonium in the nitric acid medium has the highest distribution coefficient on the TEVA resin, and can form a stable complex anion Pu(NO3)6 2- , while other cations such as Ca, Mg, Fe, Pb, U, etc. cannot form complex anions or form unstable complex anions and flow out of the resin with the solution or washing liquid, thereby realizing the separation of Pu and interfering elements and achieving the purpose of purification.

[0043] In a further preferred embodiment of the present invention, the elution treatment is to reduce the plutonium adsorbed on the TEVA extraction chromatography resin using a mixed solution of hydroxylamine hydrochloride and hydrochloric acid to obtain a plutonium eluate.

[0044] In a further preferred embodiment of the present invention, uranium in the plutonium effluent is purified and separated using UTEVA extraction resin. The reason for selecting UTEVA resin is that the stationary phase of UTEVA resin is diamyl pentylphosphonate (DAAP), and +6 uranium can be extracted by DAAP in the form of uranyl nitrate molecules.

[0045] Example 1

[0046] Step 1: Sample acid digestion

[0047] Accurately weigh 2.00g of coral sample and place it in a beaker. Use a pipette to add 500Bq 125 I and 5pg 242 Pu tracer. Add 20mL of deionized water and stir gently to make the sample powder form a suspension and mix the tracer thoroughly. Add 0.5mL of 1mol / L NaHSO3 solution to prevent iodine loss during acid dissolution, and then slowly add 6.0mL of 6.0mol / LHNO3 until the sample is dissolved. To monitor the process background, the process blank uses high-grade pure CaCO3 powder reagent and uses the same process as the sample. The purpose of the process blank is to monitor whether the sample is contaminated throughout the experimental process.

[0048] To decompose the organic matter in the sample, add 1.0 mL of 1.0 mol / L K2S2O8 solution to the dissolved sample solution, cover with a watch glass, and place the beaker on a 60-63°C hot plate to reflux for 9 hours. After the solution cools to room temperature, filter to remove insoluble matter, rinse the filter paper with deionized water several times in small amounts, and dilute the filtered solution to 50.0 g. Obtain the pretreated sample solution; take three portions from the pretreated sample solution for analysis and detection of different elements, and the remaining solution is used for 129 I. 239 Pu, 240 Pu and 236 Isolation and purification of U.

[0049] Take 1.0mL of pre-treated sample solution for testing 125 I, calculate the iodine recovery rate during acid dissolution and organic matter digestion; take 1.0mL of pretreated sample solution for use, test 127 I; Take 1.0mL of pre-treated sample solution for use, test 238 U.

[0050] Step 2 129 I and 127 Analysis and determination process of I

[0051] (1) 129 Solvent extraction enrichment and purification of I: Transfer the remaining pre-treated sample solution to a separatory funnel and rinse the beaker three times; add 0.5 mg 127 I carrier, shake well; add 0.4mL, 1.0mol / LNaHSO3 and shake well; add 3.0mol / L nitric acid to adjust to pH<2, and exhaust while shaking; add 10-15mL CCl4 and then add 0.4mL, 1.0mol / L NaNO2 in small amounts and multiple times, shake well, exhaust, and observe whether CCl4 turns red. If there is no color change, continue to add 5-10 drops of NaNO2, shake well, exhaust, and observe whether the color becomes darker, until there is no obvious color change within half a minute. Let it stand, release the CCl4 phase from the bottom of the separatory funnel into a beaker, and carry out the above process 3 times. After the extraction is completed, collect the first aqueous phase solution and the CCl4 phase; collect and combine the first aqueous phase solution into another clean beaker for use 239 Pu, 240 Pu and 236 Analysis of U.

[0052] Transfer the 15mL CCl4 phase obtained above to a clean separatory funnel, rinse the beaker with deionized water three times; add 0.2mL of 0.02mol / L NaHSO3, shake well, and exhaust; let it stand to observe whether it will turn red again; release the CCl4 phase waste liquid in the lower layer, collect the second aqueous phase solution, and then after the second aqueous phase solution is extracted and stripped, the collected second aqueous phase solutions are combined for iodine element analysis, and the stripping liquid is recovered into a 15.0mL centrifuge tube, and the separatory funnel is rinsed with deionized water twice, and the stripping liquid is combined and transferred to the centrifuge tube. The total volume of the stripping liquid is controlled within 9.0mL.

[0053] Add 0.2mL of 0.02mol / L NaHSO3 to 15mL of the second aqueous phase solution and shake well; adjust pH to <2 with 6.0mol / L nitric acid, add dropwise while bubbling; slowly add dropwise 0.5mL of 1.0mol / LAgNO3 to precipitate the iodine in the solution as AgI, bubble until the precipitation is completely produced, and let stand; centrifuge to separate the precipitate; wash the precipitate once with 3.0mol / L nitric acid and twice with deionized water. Put the precipitate in an oven and completely dry it at 70℃, then mix the dried precipitate with niobium powder at a mass ratio of 1:5, press into the copper target, and make the target source for accelerator mass spectrometry analysis.

[0054] (2) 129 AMS determination of I: After the target source required by the accelerator mass spectrometer was prepared, the 3MV accelerator mass spectrometer of Xi'an Accelerator Mass Spectrometry Center was used to measure the 129 I / 127 I atomic ratio. 127 After I was measured by ICP-MS, 129 I / 127 The atomic ratio of I is calculated by back-calculation using formula (1): 129 I.

[0055] The prepared target sample is placed in the target plate in the ion source, and the sample is sputtered by the cesium ion source. - Form injection analysis system, through 54° spherical electrostatic analyzer and 90° double focusing energy jump magnet analysis, 129 I - and 127 I - Alternately inject into the high energy accelerating tube, and in the accelerating tube argon stripper, I - The outer electrons are stripped to form iodine ions with different valence states. 5+ After re-acceleration, it is separated by a 115° high energy analysis magnet. 129 I 5+ and 127 I 5+ . 127 I 5+The charge is measured by the Faraday cup. 129 I 5+ After energy selection and momentum selection, the gas ionization detector measures its counts. All samples are measured 6 times in a cycle, each measurement lasting 5 minutes. 129 I / 127 The detection limit of I ratio measurement is 2.0×10 -14 .

[0056] In coral samples 129 The I content was calculated using formula (1).

[0057]

[0058] In the formula, R sample In the sample 129 I / 127 I atomic ratio, R blank Is the process blank 129 I / 127 I atomic ratio; 129 I sample and 127 I sample In the samples 129 I and 127 I content; 127 I carrier It is joined 127 I carrier quality; CY 125I Is adopted 125 I is the chemical recovery of iodine measured by the tracer; m sample It is the coral sample quality.

[0059] (3) 127 ICP-MS measurement of I: Take 1.0 mL of the pre-treated sample solution and dilute it 100 times with 1% NH3·H2O to 50 μg / L 133 Cs standard solution was used as internal standard in ICP-MS determination of 127 I concentration, calculated in the sample 127 I content.

[0060] In coral samples 127 The I content was calculated using formula (2).

[0061]

[0062] In the formula, CPS sample is measured by ICP-MS in the sample 127 I count, CPS blank is measured by ICP-MS in the process blank 127 I is the count; S is the sensitivity of ICP-MS measurement; DF is127 I is the dilution factor measured; CY 125I Is adopted 125 I is the chemical recovery of iodine measured by the tracer; m sample It is the coral sample quality.

[0063] Step 3: Plutonium analysis process

[0064] (1) Separation of Plutonium by Sedimentation

[0065] To the first aqueous phase solution collected after extraction, 0.5 mg Fe 3+ (FeCl3), after mixing evenly, add 10% ammonia water to adjust the pH to 9. After the brown-red precipitate appears, centrifuge to separate the co-precipitation of plutonium hydroxide, uranyl hydroxide and ferric hydroxide, thereby separating Pu and U from the matrix component. Then wash the precipitate with 50mL of 2.0mol / L sodium hydroxide solution to remove amphoteric elements such as Zn, Al, V, etc., and centrifuge to separate the precipitate. Add ultrapure water to wash the precipitate, and centrifuge at 4500rpm for 10min to obtain the precipitate. Finally, add 1.5mL of 12mol / L hydrochloric acid to dissolve the precipitate, add water to about 50mL, adjust the pH to 2.0, and obtain the plutonium column solution.

[0066] (2) Extraction resin purification of plutonium

[0067] By utilizing the property that +4-valent plutonium in nitric acid medium has the highest distribution coefficient on TEVA resin, a stable complex anion Pu(NO3)6 can be formed. 2- , while other cations such as Ca, Mg, Fe, Pb, U, etc. cannot form complex anions or form unstable complex anions and flow out of the resin with the solution or washing liquid, thereby achieving the separation of Pu and interfering elements and achieving the purpose of purification. Specifically follow the following steps:

[0068] First, adjust the plutonium of different valence states in the plutonium column solution to +4. The specific steps are as follows: add 500 mg of K2S2O5 to the plutonium column solution and stir on a magnetic stirrer for 20 minutes. The solution color turns light yellow and all high-valence plutonium (IV, V, VI) is reduced to Pu 3+ , add ammonia water to adjust the pH to 9-10, obtain Fe(OH)2 and Pu(OH)3 coprecipitate (dark green), centrifuge to remove the supernatant and separate the precipitate. Wash the precipitate with 200.0mL of ultrapure water, centrifuge for 10min, pour off the supernatant, and retain the precipitate. Add 1.5mL of 12mol / L hydrochloric acid to dissolve the precipitate. After it turns bright orange, transfer it to a 50.0mL centrifuge tube, add 6.5mL of 8mol / L nitric acid, stir the reaction for 3-5min, and adjust the volume to 30.0mL. Use the NO2 contained in nitric acid -Oxidize Pu to +4 valence and finally prepare a 3.0 mol / L nitric acid matrix solution to be loaded onto the column.

[0069] Soak TEVA resin in ultrapure water for 24 hours and store in the dark. Load 2 mL of pre-soaked TEVA resin into the chromatography column and pre-treat the resin with 20.0 mL of 3.0 mol / L nitric acid. Load the sample solution onto the column, and after the solution passes through the column, wash the resin with 120.0 mL of 3.0 mol / L nitric acid and 60.0 mL of 6.0 mol / L hydrochloric acid to remove other interfering nuclides such as U, Pb, Am, Th, etc. for Pu isotope determination. Collect all plutonium effluent here for use 236 Analysis of U.

[0070] Finally, 30.0 mL of 0.1 mol / L NH2OH·HCl-2.0 mol / L HCl was used to 4+ Reduction to Pu from resin 3+ , due to Pu 3+ Pu was eluted because it could not form complex anions. The eluent was evaporated on a hot plate at 200°C until it was nearly dry. A few drops of 14.0 mol / L nitric acid were added to heat and decompose to remove the crystallized hydroxylamine hydrochloride and HCl, reducing the isotopic interference measurement of other nuclides with chlorine with mass numbers of 239 and 240. Finally, 4 mL of 0.5 mol / L nitric acid solution was used to dissolve Pu and the ICP-MS was used for determination. 239 Pu, 240 Pu and tracer 242 Pu.

[0071] Trace plutonium isotopes in samples were determined by tandem APEX-ICP-MS with NH3-He as collision / reaction gas.

[0072] Step 4: Uranium analysis process

[0073] (1) Uranium extraction resin purification

[0074] UTEVA extraction resin was used to separate and purify uranium from plutonium effluent. The swollen UTEVA (100-200μm, Triskem International) resin was loaded into a 2.0mL standard chromatographic column (0.7cm in diameter, 5.0cm in height), and the column was pre-equilibrated with 30.0mL of 3.0mol / L HNO3. After the effluent (3.0mol / L HNO3 matrix) was loaded onto the resin, extraction chromatography was prepared for separation. The column was washed with 120.0mL of 3.0mol / L HNO3 to remove matrix ions, and then with 60.0mL of 6.0mol / L HCl to remove thorium. The UTEVA resin was used to elute the uranium adsorbed on the resin with 30.0mL of 0.025mol / L HCl to obtain a uranium eluate, and the elution flow rate was controlled at 1.0-1.5mL / min.

[0075] (2) Measurement of uranium isotopes

[0076] 238 ICP-MS measurement of U: Take 1.0 mL of the pre-treated sample solution, dilute it 100 times with 0.5 mol / L HNO3, and use it to determine the U in the solution by ICP-MS. 238 U concentration, calculated in the sample 238 U content, calculated using the same method as formula (2) 127 The calculation process of I.

[0077] 236 U measurement: The uranium eluate was placed on a hot plate at 200°C and evaporated to near dryness. Then 1.0 mL of 0.5 mol / L HNO3 was added to dissolve the sample and the volume was fixed to 4.0 mL. APEX-ICP-MS was used to determine the U in the solution in the CO2-He collision reaction gas mode. 236 U concentration, calculated in the sample 236 U content, calculated using the same method as formula (2) 127 The calculation process of I.

[0078] Example 2

[0079] Step 1: Sample acid digestion

[0080] Accurately weigh 3.00g of coral sample and place it in a beaker. Use a pipette to add 500Bq 125 I and 5pg 242Pu tracer. Add 20mL of deionized water and stir gently to make the sample powder form a suspension and mix the tracer thoroughly. Add 0.6mL of 1mol / L NaHSO3 solution to prevent iodine loss during acid dissolution, and then slowly add 7.0mL of 6.0mol / LHNO3 until the sample is dissolved. To monitor the process background, the process blank uses high-grade pure CaCO3 powder reagent and uses the same process as the sample. The purpose of the process blank is to monitor whether the sample is contaminated throughout the experimental process.

[0081] To decompose the organic matter in the sample, add 0.8 mL of 1.0 mol / L K2S2O8 solution to the dissolved sample solution, cover with a watch glass, and place the beaker on a 68-70°C hot plate to reflux for 9 hours. After the solution cools to room temperature, filter to remove insoluble matter, rinse the filter paper with deionized water several times in small amounts, and dilute the filtered solution to 50.0 g. Obtain the pretreated sample solution; take three portions from the pretreated sample solution for analysis and detection of different elements, and the remaining solution is used for 129 I. 239 Pu, 240 Pu and 236 Isolation and purification of U.

[0082] Take 1.0mL of pre-treated sample solution for testing 125 I, calculate the iodine recovery rate during acid dissolution and organic matter digestion; take 1.0mL of pretreated sample solution for use, test 127 I; Take 1.0mL of pre-treated sample solution for use, test 238 U.

[0083] Step 2 129 I and 127 Analysis and determination process of I

[0084] (1) 129 Solvent extraction enrichment and purification of I: Transfer 1.0 mL of the pretreated sample solution to a separatory funnel and rinse the beaker three times; add 0.5 mg 127I carrier, shake well; add 0.3mL, 1.0mol / LNaHSO3 and shake well; add 3.0mL, 3.0mol / L nitric acid to adjust pH=1, and exhaust while shaking; add 10mL CCl4 and then add 0.3mL, 1.0mol / L NaNO2 in small amounts and multiple times, shake well, exhaust, and observe whether CCl4 turns red. If there is no color change, continue to add 5 to 10 drops of NaNO2, shake well, exhaust, and observe whether the color becomes darker, until there is no obvious color change within half a minute. Let it stand, release the CCl4 phase from the bottom of the separatory funnel into a beaker, and carry out the above process 3 times. After the extraction is completed, collect the first aqueous phase solution and the CCl4 phase; collect and combine the first aqueous phase solution into another clean beaker for use 239 Pu, 240 Pu and 236 Analysis of U.

[0085] Transfer the 15mL CCl4 phase obtained above to a clean separatory funnel, rinse the beaker three times with deionized water; add 0.1mL of 0.02mol / L NaHSO3, shake well, and exhaust; let it stand to observe whether it will turn red again; release the CCl4 phase waste liquid in the lower layer, collect the second aqueous phase solution, and then after the second aqueous phase solution is extracted and stripped, the collected second aqueous phase solutions are combined for iodine element analysis, and the stripping liquid is recovered into a 15.0mL centrifuge tube, and the separatory funnel is rinsed with deionized water twice, and the stripping liquid is combined and transferred to the centrifuge tube. The total volume of the stripping liquid is controlled within 9.0mL.

[0086] Add 0.1mL of 0.02mol / L NaHSO3 to 15mL of the second aqueous phase solution and shake well; adjust pH to 1.5 with 6.0mol / L nitric acid, add dropwise while bubbling; slowly add dropwise 0.6mL of 1.0mol / LAgNO3 to precipitate the iodine in the solution as AgI, bubble until the precipitation is completely produced, and let stand; centrifuge to separate the precipitate; wash the precipitate once with 3.0mol / L nitric acid and twice with deionized water. Put the precipitate in an oven and completely dry it at 70℃, then mix the dried precipitate with niobium powder at a mass ratio of 1:5, press into the copper target, and make the target source for accelerator mass spectrometry analysis.

[0087] (2) 129 AMS determination of I: After the target source required by the accelerator mass spectrometer was prepared, the 3MV accelerator mass spectrometer of Xi'an Accelerator Mass Spectrometry Center was used to measure the 129 I / 127 I atomic ratio. 127 After I was measured by ICP-MS, 129 I / 127 The atomic ratio of I is calculated by back-calculation using formula (1): 129 I.

[0088] The prepared target sample is placed in the target plate in the ion source, and the sample is sputtered by the cesium ion source. - Form injection analysis system, through 54° spherical electrostatic analyzer and 90° double focusing energy jump magnet analysis, 129 I - and 127 I - Alternately inject into the high energy accelerating tube, and in the accelerating tube argon stripper, I - The outer electrons are stripped to form iodine ions with different valence states. 5+ After re-acceleration, it is separated by a 115° high energy analysis magnet. 129 I 5+ and 127 I 5+ . 127 I 5+ The charge is measured by the Faraday cup. 129 I 5+ After energy selection and momentum selection, the gas ionization detector measures its counts. All samples are measured 6 times in a cycle, each measurement lasting 5 minutes. 129 I / 127 The detection limit of I ratio measurement is 2.0×10 -14 .

[0089] In coral samples 129 The I content was calculated using formula (1).

[0090] (3) 127 ICP-MS measurement of I: Take 1.0 mL of the pre-treated sample solution and dilute it 100 times with 1% NH3·H2O to 50 μg / L 133 Cs standard solution was used as internal standard in ICP-MS determination of 127 I concentration, calculated in the sample 127 The content of I.

[0091] In coral samples 127 The I content was calculated using formula (2).

[0092] Step 3: Plutonium analysis process

[0093] (1) Separation of Plutonium by Sedimentation

[0094] To the 15 mL first aqueous phase solution collected after extraction, 0.5 mg Fe 3+(FeCl3), after mixing evenly, add 10% ammonia water to adjust pH=8. After the brown-red precipitate appears, centrifuge to separate the co-precipitation of plutonium hydroxide, uranyl hydroxide and ferric hydroxide, thereby separating Pu and U from the matrix component. Then wash the precipitate with 50mL 2.0mol / L sodium hydroxide solution to remove amphoteric elements such as Zn, Al, V, etc., and centrifuge to separate the precipitate. Add ultrapure water to wash the precipitate, and centrifuge at 4500rpm for 10min to obtain the precipitate. Finally, add 1.5mL 12mol / L hydrochloric acid to dissolve the precipitate, add water to about 50mL, adjust pH=2.0, and obtain the plutonium column solution.

[0095] (2) Extraction resin purification of plutonium

[0096] By utilizing the property that +4-valent plutonium in nitric acid medium has the highest distribution coefficient on TEVA resin, a stable complex anion Pu(NO3)6 can be formed. 2- , while other cations such as Ca, Mg, Fe, Pb, U, etc. cannot form complex anions or form unstable complex anions and flow out of the resin with the solution or washing liquid, thereby achieving the separation of Pu and interfering elements and achieving the purpose of purification. Specifically follow the following steps:

[0097] First, adjust the plutonium of different valence states in the plutonium column solution to +4. The specific steps are as follows: add 500 mg of K2S2O5 to the plutonium column solution and stir on a magnetic stirrer for 20 minutes. The solution color turns light yellow and all high-valence plutonium (IV, V, VI) is reduced to Pu 3+ , add ammonia water to adjust the pH to 9, obtain Fe(OH)2 and Pu(OH)3 coprecipitate (dark green), centrifuge to remove the supernatant and separate the precipitate. Wash the precipitate with 200.0mL of ultrapure water, centrifuge for 10min, pour off the supernatant, and retain the precipitate. Add 1.5mL of 12mol / L hydrochloric acid to dissolve the precipitate. After it turns bright orange, transfer it to a 50.0mL centrifuge tube, add 6.5mL of 8mol / L nitric acid, stir the reaction for 3min, and adjust the volume to 30.0mL. Using the NO2 contained in nitric acid - Oxidize Pu to +4 valence, and finally prepare a 3.0 mol / L nitric acid matrix solution, wait for loading on the column after it reaches room temperature.

[0098] Soak the TEVA resin in ultrapure water for 24 hours and store it away from light. Load 2 mL of the pre-soaked TEVA resin into the chromatography column and pretreat the resin with 18.0 mL of 3.0 mol / L nitric acid. Load the sample solution onto the column, and after the solution passes through the column, wash the resin with 125.0 mL of 3.0 mol / L nitric acid and 62.0 mL of 6.0 mol / L hydrochloric acid to remove other interfering nuclides such as U, Pb, Am, Th, etc. that interfere with the Pu isotope determination. All plutonium effluent is collected here for 236 Analysis of U.

[0099] Finally, 32.0 mL of 0.1 mol / L NH2OH·HCl and 2.0 mol / L HCl were used to 4+ Reduction to Pu from resin 3+ , due to Pu 3+ Pu was eluted because it could not form complex anions. The eluent was evaporated on a hot plate at 200°C until it was nearly dry. A few drops of 14.0 mol / L nitric acid were added to heat and decompose to remove the crystallized hydroxylamine hydrochloride and HCl, reducing the isotopic interference measurement of other nuclides with chlorine with mass numbers of 239 and 240. Finally, 3 mL of 0.5 mol / L nitric acid solution was used to dissolve Pu and the ICP-MS was used for determination. 239 Pu, 240 Pu and tracer 242 Pu.

[0100] Determination of trace plutonium isotopes in samples by APEX-ICP-MS with NH3-He as collision / reaction gas

[0101] Step 4: Uranium analysis process

[0102] (1) Uranium extraction resin purification

[0103] UTEVA extraction resin was used to separate and purify uranium from plutonium effluent. The swollen UTEVA (100-200μm, Triskem International) resin was loaded into a 2.0mL standard chromatographic column (0.7cm in diameter, 5.0cm in height), and the column was pre-equilibrated with 32.0mL of 3.0mol / L HNO3. After the effluent (3.0mol / L HNO3 matrix) was loaded onto the resin, extraction chromatography was prepared. The column was washed with 125.0mL of 3.0mol / L HNO3 to remove matrix ions, and then with 65.0mL of 6.0mol / L HCl to remove thorium. The UTEVA resin was eluted with 32.0mL of 0.025mol / L HCl to obtain a uranium eluate, and the elution flow rate was controlled at 1.0mL / min.

[0104] (2) Measurement of uranium isotopes

[0105] 238 ICP-MS measurement of U: Take 1.0 mL of the pre-treated sample solution, dilute it 100 times with 0.5 mol / L HNO3, and use it to determine the U in the solution by ICP-MS. 238 U concentration, calculated in the sample 238 U content, calculated using the same method as formula (2) 127 The calculation process of I.

[0106] 236 U measurement: The uranium eluate was placed on a hot plate at 200°C and evaporated to near dryness. Then 1.2 mL of 0.5 mol / L HNO3 was added to dissolve the sample and the volume was fixed to 4.0 mL. APEX-ICP-MS was used to determine the U in the solution in the CO2-He collision reaction gas mode. 236 U concentration, calculated in the sample 236 U content, calculated using the same method as formula (2) 127 The calculation process of I.

[0107] Example 3

[0108] Step 1: Sample acid digestion

[0109] Accurately weigh 5.00g of coral sample and place it in a beaker. Use a pipette to add 500Bq 125 I and 5pg 242 Pu tracer. Add 20mL of deionized water and stir gently to make the sample powder form a suspension and mix the tracer thoroughly. Add 0.3mL of 1mol / L NaHSO3 solution to prevent iodine loss during acid dissolution, and then slowly add 5.0mL of 6.0mol / LHNO3 until the sample is dissolved. To monitor the process background, the process blank uses high-grade pure CaCO3 powder reagent and uses the same process as the sample. The purpose of the process blank is to monitor whether the sample is contaminated throughout the experimental process.

[0110] To decompose the organic matter in the sample, add 1.2mL of 1.0mol / L K2S2O8 solution to the dissolved sample solution, cover with a watch glass, and place the beaker on a 65℃~68℃ hot plate to reflux for 9h. After the solution cools to room temperature, filter to remove insoluble matter, rinse the filter paper with deionized water several times in small amounts, and dilute the filtered solution to 50.0g. Obtain the pretreated sample solution; take three portions from the pretreated sample solution for analysis and detection of different elements, and the remaining solution is used for 129 I. 239 Pu, 240 Pu and 236Isolation and purification of U.

[0111] Take 1.0mL of pre-treated sample solution for testing 125 I, calculate the iodine recovery rate during acid dissolution and organic matter digestion; take 1.0mL of pretreated sample solution for use, test 127 I; Take 1.0mL of pre-treated sample solution for use, test 238 U.

[0112] Step 2 129 I and 127 Analysis and determination process of I

[0113] (1) 129 Solvent extraction enrichment and purification of I: Transfer 1.0 mL of the pretreated sample solution to a separatory funnel and rinse the beaker three times; add 0.5 mg 127 I carrier, shake well; add 0.6mL, 1.0mol / LNaHSO3 and shake well; add 3.0mL, 3.0mol / L nitric acid to adjust the pH (pH<2), and exhaust while shaking; add 15mL CCl4 and then add 0.5mL, 1.0mol / L NaNO2 in small amounts and multiple times, shake well, exhaust, and observe whether CCl4 turns red. If there is no color change, continue to add 5 to 10 drops of NaNO2, shake well, exhaust, and observe whether the color becomes darker, until there is no obvious color change within half a minute. Let it stand, release the CCl4 phase from the bottom of the separatory funnel into a beaker, and carry out the above process 3 times. After the extraction is completed, collect the first aqueous phase solution and the CCl4 phase; collect and combine the first aqueous phase solution into another clean beaker for use 239 Pu, 240 Pu and 236 Analysis of U.

[0114] Transfer the 15mL CCl4 phase obtained above to a clean separatory funnel, rinse the beaker three times with deionized water; add 0.2mL of 1.0mol / L NaHSO3, shake well, and exhaust; let it stand to observe whether it will turn red again; release the CCl4 phase waste liquid in the lower layer, collect the second aqueous phase solution, and then after the second aqueous phase solution is extracted and stripped, the collected second aqueous phase solutions are combined for iodine element analysis, and the stripping liquid is recovered into a 15.0mL centrifuge tube, and the separatory funnel is rinsed with deionized water twice, and the stripping liquid is transferred to the centrifuge tube. The total volume of the stripping liquid is controlled within 9.0mL.

[0115] Add 0.2mL of 1.0mol / L NaHSO3 to 15mL of the second aqueous phase solution and shake well; adjust pH to 2 with 6.0mol / L nitric acid, add dropwise while bubbling; slowly add dropwise 0.4mL of 1.0mol / LAgNO3 to precipitate the iodine in the solution as AgI, bubble until the precipitation is completely produced, and let stand; centrifuge to separate the precipitate; wash the precipitate once with 3.0mol / L nitric acid and twice with deionized water. Put the precipitate in an oven and completely dry it at 70℃, then mix the dried precipitate with niobium powder at a mass ratio of 1:5, press into the copper target, and make the accelerator mass spectrometry target source.

[0116] (2) 129 AMS determination of I: After the target source required by the accelerator mass spectrometer was prepared, the 3MV accelerator mass spectrometer of Xi'an Accelerator Mass Spectrometry Center was used to measure the 129 I / 127 I atomic ratio. 127 After I was measured by ICP-MS, 129 I / 127 The atomic ratio of I is calculated by back-calculation using formula (1): 129 I.

[0117] The prepared target sample is placed in the target plate in the ion source, and the sample is sputtered by the cesium ion source. - Form injection analysis system, through 54° spherical electrostatic analyzer and 90° double focusing energy jump magnet analysis, 129 I - and 127 I - Alternately inject into the high energy accelerating tube, and in the accelerating tube argon stripper, I - The outer electrons are stripped to form iodine ions with different valence states. 5+ After re-acceleration, it is separated by a 115° high energy analysis magnet. 129 I 5+ and 127 I 5+ . 127 I 5+ The charge is measured by the Faraday cup. 129 I 5+ After energy selection and momentum selection, the gas ionization detector measures its counts. All samples are measured 6 times in a cycle, each measurement lasting 5 minutes. 129 I / 127 The detection limit of I ratio measurement is 2.0×10 -14 .

[0118] In coral samples 129 The I content was calculated using formula (1).

[0119] (3)127 ICP-MS measurement of I: Take 1.0 mL of the pre-treated sample solution and dilute it 100 times with 1% NH3·H2O to 50 μg / L 133 Cs standard solution was used as internal standard in ICP-MS determination of 127 I concentration, calculated in the sample 127 The content of I.

[0120] In coral samples 127 The I content was calculated using formula (2).

[0121] Step 3: Plutonium analysis process

[0122] (1) Separation of Plutonium by Sedimentation

[0123] To the 15 mL first aqueous phase solution collected after extraction, 0.5 mg Fe 3+ (FeCl3), after mixing evenly, add 10% ammonia water to adjust the pH to 9. After the brown-red precipitate appears, centrifuge to separate the co-precipitation of plutonium hydroxide, uranyl hydroxide and ferric hydroxide, thereby separating Pu and U from the matrix component. Then wash the precipitate with 50mL of 2.0mol / L sodium hydroxide solution to remove amphoteric elements such as Zn, Al, V, etc., and centrifuge to separate the precipitate. Add ultrapure water to wash the precipitate, and centrifuge at 4500rpm for 10min to obtain the precipitate. Finally, add 2mL of 12mol / L hydrochloric acid to dissolve the precipitate, add water to about 50mL, adjust the pH to 2.0, and obtain the plutonium column solution.

[0124] (2) Extraction resin purification of plutonium

[0125] By utilizing the property that +4-valent plutonium in nitric acid medium has the highest distribution coefficient on TEVA resin, a stable complex anion Pu(NO3)6 can be formed. 2- , while other cations such as Ca, Mg, Fe, Pb, U, etc. cannot form complex anions or form unstable complex anions and flow out of the resin with the solution or washing liquid, thereby achieving the separation of Pu and interfering elements and achieving the purpose of purification. Specifically follow the following steps:

[0126] First, adjust the plutonium of different valence states in the plutonium column solution to +4. The specific steps are as follows: add 500 mg of K2S2O5 to the plutonium column solution and stir on a magnetic stirrer for 20 minutes. The solution color turns light yellow and all high-valence plutonium (IV, V, VI) is reduced to Pu 3+, add ammonia water to adjust the pH to 10, obtain Fe(OH)2 and Pu(OH)3 coprecipitate (dark green), centrifuge to remove the supernatant and separate the precipitate. Wash the precipitate with 200.0mL of ultrapure water, centrifuge for 10min, pour off the supernatant, and retain the precipitate. Add 1.5mL of 12mol / L hydrochloric acid to dissolve the precipitate. After it turns bright orange, transfer it to a 50.0mL centrifuge tube, add 6.5mL of 8mol / L nitric acid, stir the reaction for 5min, and adjust the volume to 30.0mL. Using the NO2 contained in nitric acid - Oxidize Pu to +4 valence, and finally prepare a 3.0 mol / L nitric acid matrix solution, wait for loading on the column after it reaches room temperature.

[0127] Soak TEVA resin in ultrapure water for 24 hours and store in the dark. Load 2 mL of pre-soaked TEVA resin into the chromatography column and pre-treat the resin with 22.0 mL of 3.0 mol / L nitric acid. Load the sample solution onto the column, and after the solution passes through the column, wash the resin with 123.0 mL of 3.0 mol / L nitric acid and 65.0 mL of 6.0 mol / L hydrochloric acid to remove other interfering nuclides such as U, Pb, Am, Th, etc. that interfere with Pu isotope determination. All plutonium effluent is collected here for 236 Analysis of U.

[0128] Finally, 29.0 mL of 0.1 mol / L NH2OH·HCl and 2.0 mol / L HCl were used to 4+ Reduction to Pu from resin 3+ , due to Pu 3+ Pu was eluted because it could not form complex anions. The eluent was evaporated on a hot plate at 200°C until it was nearly dry. A few drops of 14.0 mol / L nitric acid were added to heat and decompose to remove the crystallized hydroxylamine hydrochloride and HCl, reducing the interference of other nuclides with chlorine to form isobaric isotopes with mass numbers of 239 and 240. Finally, 3.5 mL of 0.5 mol / L nitric acid solution was used to dissolve Pu and the ICP-MS was used for determination. 239 Pu, 240 Pu and tracer 242 Pu.

[0129] Trace plutonium isotopes in samples were determined by tandem APEX-ICP-MS with NH3-He as collision / reaction gas.

[0130] Step 4: Uranium analysis process

[0131] (1) Uranium extraction resin purification

[0132] UTEVA extraction resin was used to separate and purify uranium from plutonium effluent. Take the swollen UTEVA (100-200μm, Triskem International) resin and load it into a 2.0mL standard chromatographic column (0.7cm in diameter, 5.0cm in height). Use 29.0mL of 3.0mol / L HNO3 to pre-equilibrate the column. After loading the effluent (3.0mol / L HNO3 matrix) onto the resin, prepare for extraction chromatography. Use 123.0mL of 3.0mol / L HNO3 to wash the column to remove matrix ions, and then use 63.0mL of 6.0mol / L HCl to wash the column to remove thorium. Use 35.0mL of 0.025mol / L HCl to elute the uranium adsorbed on the resin with UTEVA resin to obtain a uranium eluate. The elution flow rate is controlled at 1.5mL / min.

[0133] (2) Measurement of uranium isotopes

[0134] 238 ICP-MS measurement of U: Take 1.0 mL of the pre-treated sample solution, dilute it 100 times with 0.5 mol / L HNO3, and use it to determine the U in the solution by ICP-MS. 238 U concentration, calculated in the sample 238 U content, calculated using the same method as formula (2) 127 The calculation process of I.

[0135] 236 U measurement: The uranium eluate was placed on a hot plate at 200°C and evaporated to near dryness. Then 0.8 mL of 0.5 mol / L HNO3 was added to dissolve the sample and the volume was fixed to 4.0 mL. APEX-ICP-MS was used to determine the U in the solution in the CO2-He collision reaction gas mode. 236 U concentration, calculated in the sample 236 U content, calculated using the same method as formula (2) 127 The calculation process of I.

[0136] In order to further demonstrate the analytical effect of the present invention, actual coral samples were tested and analyzed using the method of Example 1.

[0137] The present invention separates and extracts iodine, plutonium and uranium isotopes from coral samples by solvent extraction and chromatographic separation technology, and prepares the target source. AMS is used to measure iodine-129, APEX-ICP-MS is used to measure plutonium-239, 240 and uranium-236, and ICP-MS is used to measure uranium-238. A set of coral sample is established. 129 I- 239,240 Pu- 236,238The high-sensitivity mass spectrometry technology of U was used, and the combined process was applied to the analysis of actual coral samples. The analysis results are shown in Tables 1 and 2.

[0138] Table 1 Detection limits and recoveries of coral samples

[0139] Radionuclides Testing methods Detection limit unit Recovery rate, % <![CDATA[ 127 I]]> ICP-MS 2.03 <![CDATA[ngg -1 ]]> >95 <![CDATA[ 129 I]]> AMS 3386 <![CDATA[atomg -1 ]]> 77.2 <![CDATA[ 236 In]]> ICP-MS 0.45 <![CDATA[fgg -1 ]]> 63.2 <![CDATA[ 238 In]]> ICP-MS 0.018 <![CDATA[ngg -1 ]]> >98 <![CDATA[ 239 Pu]]> ICP-MS 0.37 <![CDATA[fgg -1 ]]> 66.7 <![CDATA[ 240 Pu]]> ICP-MS 0.09 <![CDATA[fgg -1 ]]> 66.7

[0140] It can be seen from Table 1 that the iodine-plutonium-uranium joint analysis method in coral samples provided by the present invention can achieve a high recovery rate of iodine, plutonium and uranium isotopes, with a recovery rate of 63% to 98%.

[0141] Table 2 Measurement results of parallel coral samples

[0142]

[0143]

[0144] Table 2 shows the results of parallel coral samples. 129 I. 239,240 Pu, 236 U content, and 129 I / 127 I. 240 Pu / 239 Pu and 236 U / 238 The isotope ratio data of U. The results show that 236 With the exception of the U data, the parallelism of the coral sample analysis was good. 127 I and 238 The analytical accuracy of U is less than 3%. 129 The analytical accuracy of I is within 10%, 239,240 Pu, 236 U due to plutonium isotopes and 236 The U concentration is extremely low and its analysis accuracy is relatively high.

[0145] The method of Example 1 is used below to analyze the Shanshan samples collected from Wenchang, Hainan.

[0146] Table 3 Analysis results of iodine-plutonium-uranium radioisotopes in Wenchang coral samples

[0147] Sample No. Wenchang 1 Wenchang 2 Wenchang 3 Wenchang 4 Wenchang 5 <![CDATA[ 127 I,μg / g]]> 5.59±0.04 5.51±0.05 5.52±0.05 5.41±0.04 5.66±0.07 <![CDATA[ 129 I, 10 5 atom / g]]> 4.09±0.28 5.77±0.29 7.94±0.37 8.37±0.46 7.79±0.49 <![CDATA[ 129 I / 127 I atomic ratio, 10 -11 ]]> 1.54±0.11 2.20±0.12 3.04±0.15 3.26±0.18 2.90±0.19 <![CDATA[ 236 U, 10 7 atom / kg]]> 9.7±0.6 19.6±1.6 12.9±2.7 10.5±1.4 10.2±2.7 <![CDATA[ 238 U,μg / g]]> 1.78±0.01 1.88±0.01 1.86±0.01 1.69±0.01 1.76±0.01 <![CDATA[ 236 U / 238 U atomic ratio, 10 -9 ]]> 2.15±0.13 4.13±0.33 2.74±0.58 2.46±0.33 2.29±0.60 <![CDATA[ 239 Pu,mBq / kg]]> 82.6±6.7 83.3±2.9 42.9±1.6 24.3±1.7 14.4±1.0 <![CDATA[ 240 Pu,mBq / kg]]> 102±15 83.4±3.4 38.7±2.4 23.7±2.0 12.4±1.5 <![CDATA[ 240 Pu / 239 Pu atomic ratio]]> 0.337±0.055 0.272±0.009 0.245±0.017 0.265±0.022 0.234±0.033

[0148] APEX-ICP-QQQ-MS and AMS were used to analyze the 127 I. 129 I. 240,239 Pu, 238 U and 236U was determined. After the samples were processed and analyzed according to the method of Example 1, the data in Table 3 were obtained, which are the first batch of data reported for six nuclides at the same time. 129 The concentration range of I is 4.09×10 5 ~8.37×10 5 atoms / g, with an average value of 6.79×10 5 atom / g; 129 I / 127 The level of I is 1.54×10 -11 ~3.26×10 - 11 atom / atom, and seawater and sediments in the South China Sea 129 I / 127 I's research is consistent with the literature reports. 238 The concentration of U was in the range of 1.69 to 1.88 μg g -1 , 236 The concentration level of U is 9.7×10 7 ~19.6×10 7 atoms / g, which is consistent with the uranium levels in other corals in the South China Sea reported in the literature. 239 Pu and 240 The Pu specific activity ranges are 14.4~83.3mBq / kg and 12.4~102mBq / kg, 240 Pu / 239 The Pu range is 0.234 to 0.337. The characteristic isotope ratios of iodine, plutonium and uranium indicate that the Wenchang coral samples reflect the significant impact of human nuclear activities. Pu and U mainly come from the US Pacific Proving Ground (PPG) located in the Marshall Islands in the Pacific Ocean. 240 Pu / 239 The characteristic ratio of Pu is 0.300-0.360, with a small amount coming from atmospheric deposition in the Northern Hemisphere (0.180±0.001) and the equatorial region of the Northern Hemisphere (0.178±0.002).

[0149] The study shows that the combined analysis method of iodine-plutonium-uranium radioisotopes in coral samples provided by the present invention can effectively detect the three elements of iodine, plutonium and uranium in coral samples, and when testing, one sample can be used for testing, which can reduce the amount of sample used by more than 10 times. The study also shows that the combined analysis process provided by the present invention can be used for the study of radioactivity in my country's marine environment, serve my country's nuclear environmental safety monitoring, and be used for radiation dose estimation in nuclear incidents and emergencies, and can provide a scientific basis for government decision-making and public safety.

[0150] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0151] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A method for the combined analysis of iodine-plutonium-uranium radioisotopes in coral samples. It is characterized in that The following steps are involved: After the coral sample is soaked, add 125 I tracer and 242 Pu tracer, after being mixed evenly, was acid dissolved, and then the organic matter was removed to obtain the pre-treated sample solution; the pre-treated sample solution was determined by inductively coupled plasma mass spectrometry to obtain the 127 I and 238 U content; Add to the pre-treated sample solution 127 I carrier and reducing agent, adding oxidant under acidic conditions to extract the first aqueous phase solution and the carbon tetrachloride phase solution; Re-extracting the carbon tetrachloride phase solution to obtain a second aqueous phase solution; The second aqueous phase solution is subjected to precipitation reaction to obtain a precipitate, and the precipitate is made into a target sample, and the target sample is measured by accelerator mass spectrometry to obtain the content of the coral sample. 129 I content; The first aqueous phase solution is subjected to precipitation separation and chromatographic purification to obtain a plutonium effluent, which is then eluted to obtain a plutonium eluate; NH 3 -He was used as collision / reaction gas, and APEX and inductively coupled plasma mass spectrometry were used to determine the plutonium eluate in the coral sample. 239 Pu and 240 Pu content; The plutonium effluent is subjected to chromatographic purification, and the uranium eluate is obtained after elution. 2 -He was used as collision / reaction gas, and APEX and ICP-MS were connected in series to determine the concentration of 236 U content.

2. The method for combined analysis of iodine-plutonium-uranium radioisotopes in coral samples according to claim 1, It is characterized in that The steps of removing organic matter are as follows: adding potassium persulfate to the sample after acid dissolution, and refluxing at 60-70° C. to remove the organic matter.

3. The method for combined analysis of iodine-plutonium-uranium radioisotopes in coral samples according to claim 1, It is characterized in that The precipitation reaction method is: adding a reducing agent to the second aqueous phase solution, adjusting the pH to less than 2, and then adding silver nitrate to form a precipitate.

4. The method for combined analysis of iodine-plutonium-uranium radioisotopes in coral samples according to claim 1, It is characterized in that The precipitation separation method is: adding a compound containing trivalent iron to the first aqueous phase solution, adjusting the pH to 8-9, and separating to obtain a precipitate.

5. The method for combined analysis of iodine-plutonium-uranium radioisotopes in coral samples according to claim 4, It is characterized in that The chromatographic purification method is as follows: after the precipitate is dissolved and oxidized, it is purified using TEVA extraction chromatographic resin to separate and obtain the plutonium effluent.

6. The method for combined analysis of iodine-plutonium-uranium radioisotopes in coral samples according to claim 5, It is characterized in that The elution treatment is to use a mixed solution of hydroxylamine hydrochloride and hydrochloric acid to reduce the plutonium adsorbed on the TEVA extraction chromatography resin to obtain a plutonium eluate.

7. The method for combined analysis of iodine-plutonium-uranium radioisotopes in coral samples according to claim 1, It is characterized in that The plutonium effluent is purified by chromatography using UTEVA resin.

8. The method for combined analysis of iodine-plutonium-uranium radioisotopes in coral samples according to claim 1, It is characterized in that 127 The content of I was determined by pre-treating the sample solution with NH 3 ·H 2 After dilution, 133 Cs standard solution was used as the internal standard and the content of 127 I concentration, calculate the sample 127 I content.

9. The method for combined analysis of iodine-plutonium-uranium radioisotopes in coral samples according to claim 1, It is characterized in that 238 The content of U was determined by diluting the sample solution with nitric acid and then using inductively coupled plasma mass spectrometry to determine the content of U in the solution. 238 U concentration, calculated in the sample 238 U content.

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