Method for jointly determining plutonium 238, 239 +240 and neptun-237 in aerosol by taking Pu-236 as yield tracer

Abstract

The invention relates to a method for jointly determining plutonium 238, 239 + 240 and neptun-237 in aerosol by taking Pu-236 as a yield tracer agent, which comprises the following steps: step 1, sample pretreatment: cutting an aerosol sample into pieces, adding 236Pu, ashing, and leaching with a nitric acid solution A; step 2, valence state adjustment: adjusting the acidity of the leaching solution, and sequentially adding a hydroxylamine hydrochloride solution, a ferrous sulfamate solution and a sodium nitrite solution to adjust the valence state of nuclide; step 3, separation and purification: separating and purifying by adopting a TEVA resin column, leaching by using a nitric acid solution B and a hydrochloric acid solution, and desorbing by using an HCl-HF solution; and 4, the desorption solution is subjected to electro-deposition to prepare a source, and a low background alpha spectrometer is adopted for measurement of plutonium 238, 239 + 240 and neptun-237. The detection method is high in sensitivity, the recovery rate of the neptun-237 is high, and the blank of joint analysis of plutonium 238, 239 + 240 and neptun-237 is filled.

Description

Technical Field

[0001] The invention belongs to the technical field of radioactive material detection, and in particular relates to a method for jointly determining plutonium-238, 239+240 and neptunium-237 in aerosol by using Pu-236 as a yield tracer. Background Art

[0002] In recent years, as my country's awareness of environmental protection has increased, the public has become more and more concerned about the environmental impact of nuclear facility operations. In the radiation environment monitoring of nuclear facilities such as nuclear fuel reprocessing plants, it is necessary to monitor transuranic nuclides and other radioactive nuclides in aerosols. Neptunium (Np) and plutonium (Pu) are two key transuranic actinide elements that can be produced by uranium capturing neutrons in reactors or by the decay of other transuranic elements. Among them, neptunium-237 and plutonium-239 have a half-life (T 1 / 2 ) Length [T 1 / 2 ( 237 Np)=2.14×10 6 a,T 1 / 2 ( 239 Pu)=24110a] and strong radiotoxicity, which poses great potential harm to the environment. Therefore, the detection of plutonium and neptunium in aerosols is crucial for environmental monitoring.

[0003] However, due to the extremely low content of plutonium and neptunium radionuclides in aerosols, a large number of aerosol samples are often required to meet the analysis requirements (usually 10,000 m3 of a single sample is required). 3 , collection time 8-10 days), and samples need to be collected at multiple points during the monitoring process. The collected samples also need to be loaded and transported back to the laboratory for processing, which undoubtedly increases the workload and time of on-site sampling and laboratory analysis. Due to its low content in the sample and limited by the measurement method, the chemical separation and purification process of a single nuclide is relatively complicated and time-consuming; therefore, providing the sensitivity of nuclide detection is crucial for the detection of low-level radionuclides. In addition, in the radiochemical analysis process, in order to ensure the accuracy of the analysis results of the nuclides to be tested, it is usually necessary to add appropriate isotopes as chemical recovery tracers before chemical treatment of the samples to correct the recovery of the analytical measurement results; although neptunium has 22 isotopes, most of them are short-lived nuclides with extremely short half-lives (<1d), which are not easy to obtain and preserve, and are less used. How to determine the recovery rate of neptunium in samples is also a very critical research content. Summary of the invention

[0004] The purpose of the present invention is to overcome the defects in the prior art and provide a method for jointly determining plutonium-238, 239+240 and neptunium-237 in aerosol using Pu-236 as a yield tracer. The detection method has high sensitivity and a high recovery rate of neptunium-237.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0006] A method for jointly determining plutonium-238, 239+240 and neptunium-237 in aerosol using Pu-236 as a yield tracer comprises the following steps:

[0007] Step 1: Sample pretreatment: Cut the aerosol sample into pieces and add 236 Pu is used as an isotope tracer, and after ashing treatment, it is leached with nitric acid solution A to obtain a leaching solution;

[0008] Step 2, valence adjustment: after adjusting the acidity of the leaching solution obtained in step 1, add hydroxylamine hydrochloride solution for reduction treatment, add ferrous aminosulfonate solution for further reduction treatment, and add sodium nitrite solution for oxidation treatment to adjust the valence of the nuclide;

[0009] Step 3, separation and purification: the sample solution obtained after adjusting the nuclide valence state in step 2 is separated and purified using a TEVA resin column, eluted with a nitric acid solution B and a hydrochloric acid solution, desorbed with an HCl-HF solution, and the desorbed liquid is collected;

[0010] Step 4: Electrodeposit the desorption liquid collected in step 3 in an ammonium sulfate system to prepare a source, and then use a low-background alpha spectrometer to measure plutonium-238, 239+240 and neptunium-237, and calculate the radioactivity concentrations of plutonium-238, 239+240 and neptunium-237 in the sample solution according to the alpha spectrometer counts of the tracer and the nuclide being measured and the known activity of the tracer.

[0011] As a further technical solution, in step 1, the leaching is performed twice, and the filtrates from the two times are combined to obtain a leaching solution;

[0012] As a further technical solution, in step 1, the concentration of the nitric acid solution A used for leaching is 6-9 mol / L (preferably 7.5 mol / L);

[0013] In step 1, the ashing treatment is carried out in a muffle furnace at a temperature of 600-700° C. (preferably 650° C.);

[0014] As a further technical solution, in step 1, leaching with nitric acid solution A is performed by reflux leaching on a hot plate at 150-200° C. (preferably 170° C.).

[0015] As a further technical solution, in step 2, the acidity of the leaching solution is adjusted to 3 mol / L;

[0016] As a further technical solution, in step 2, the concentration of the hydroxylamine hydrochloride solution is 1-3 mol / L (preferably 2.0 mol / L), and the reduction treatment time is 10-30 min (preferably 10 min);

[0017] As a further technical solution, in step 2, the concentration of the ferrous sulfamate solution is 1-3 mol / L (preferably 2.5 mol / L), and the reduction time is 10-30 min (preferably 30 min);

[0018] As a further technical solution, in step 2, the concentration of the sodium nitrite solution is 3-5 mol / L (preferably 4 mol / L), and the oxidation time is 10-30 min (preferably 10 min).

[0019] As a further technical solution, in step 2, the valence states of plutonium-238, 239+240 and neptunium-237 in the sample are adjusted to be positive tetravalent.

[0020] As a further technical solution, in step 2, the concentration of nitric acid solution B is 2-4 mol / L (preferably 3.0 mol / L); the concentration of hydrochloric acid solution is 8-10 mol / L (preferably 9 mol / L);

[0021] As a further technical solution, in the HCl-HF solution, the concentration of HCl is 0.34-0.38 mol / L (preferably 0.36 mol / L), and the concentration of HF is 0.008-0.012 mol / L (preferably 0.01 mol / L).

[0022] As a further technical solution, in step 5, the pH of the ammonium sulfate system is 2-3 (preferably 2.2), and the current of the electrodeposition source is 900-1200 mA / cm 2 ; The electrodeposition time is 1.5-2.5h (preferably 2h).

[0023] As a further technical solution, based on the alpha spectrometer counts of the tracer and the nuclide being tested and the known activity of the tracer, the calculation formula for calculating the radioactivity concentration of plutonium-238, 239+240 and neptunium-237 in the sample solution being tested is as follows:

[0024]

[0025] Where:

[0026] A---Activity concentration of plutonium-238, 239+240 or neptunium-237 in the sample;

[0027] O---The count of plutonium-238, 239+240 or neptunium-237 in the sample;

[0028] E---Detection efficiency of the instrument;

[0029] Y---Full radiochemical recovery rate of plutonium-236;

[0030] V---the volume of the sample used, m 3 .

[0031] As a further technical solution, the formula for calculating the full radiochemical recovery rate of plutonium-236 is as follows:

[0032]

[0033] Where:

[0034] N1---the activity of plutonium-236 in the sample source; Bq

[0035] N0---the activity of plutonium-236 added to the sample; Bq.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] 1. Since neptunium (Np) and plutonium (Pu) have complex electronic structures, have multiple oxidation states from III to VII (VII mainly exists in strong alkaline solutions), and have extremely complex chemical behaviors, the following valence state combinations may exist: neptunium (VI)-plutonium (IV), neptunium (V)-plutonium (IV), neptunium (IV)-plutonium (III) and neptunium (IV)-plutonium (IV), etc., they have a great interference with the detection of plutonium-238, 239+240 and neptunium-237. In order to solve the above problems, the valence state of the nuclides is determined by adjusting the acidity, using hydroxylamine hydrochloride solution for reduction treatment, adding ferrous aminosulfonate solution for further reduction treatment, and adding sodium nitrite solution for oxidation treatment. The different distribution ratios of neptunium and plutonium with different valence states on the resin are used to select the best combination for extraction and separation, which can realize the separation of neptunium and plutonium from fragment elements and reduce the interference of fragment elements on the determination of plutonium-238, 239+240 and neptunium-237.

[0038] 2. The present invention studies the simultaneous analysis method of plutonium and neptunium in aerosols and for the first time creates a method for the joint determination of plutonium-238, 239+240 and neptunium-237 in aerosols using Pu-236 as a yield tracer. This solves the problem of the lack of accurate and reliable analysis methods due to the extremely low content of plutonium isotopes in aerosols, the great difficulty in analysis, and the energy overlap of plutonium isotopes and neptunium. It fills the gap in the joint analysis and detection technology of plutonium-238, 239+240 and neptunium-237, and also provides technical support for research such as environmental assessment and dose estimation, thereby protecting the environment and personnel health.

[0039] In summary, the present invention actually analyzes neptunium-237 as an "isotope" of plutonium. Pu-236 is used as a yield tracer to conduct a joint analysis of plutonium-238, 239+240 and neptunium-237 in aerosols, thereby improving the sensitivity and recovery rate of detection, while reducing the amount of aerosol sampling, alleviating the on-site workload and improving the sampling efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 The present invention is a flowchart of a method for jointly determining plutonium-238, 239+240 and neptunium-237 in aerosol using Pu-236 as a yield tracer in one embodiment of the present invention. DETAILED DESCRIPTION

[0041] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. 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.

[0042] In the present invention,

[0043] Aerosol samples: collected at a nuclear facility in my country, using an Anderson sampler with a flow rate of 50L / min to obtain the tested samples;

[0044] Unless otherwise specified, the raw materials used in the present invention are commercially available.

[0045] Example 1

[0046] A method for the combined determination of plutonium-238, 239+240 and neptunium-237 in aerosols using Pu-236 as a yield tracer, such as Figure 1 As shown, the following steps are included:

[0047] Step 1: Sample pretreatment: Cut the aerosol sample into pieces and add 236 Pu( 236 Activity of Pu standard solution: 0.101332 Bq / mL after correction), after ashing treatment at 650℃ in a muffle furnace for 8h, transfer to a conical flask, add 7.5mol / L nitric acid solution, reflux and leaching on a 170℃ hot plate twice, adding 25mL of 7.5mol / L nitric acid solution each time, and combine the extracts.

[0048] Step 2, valence state adjustment: add 0.5 mL of hydroxylamine hydrochloride solution to the leaching solution obtained in step 1, and perform reduction treatment for 10 minutes; add 0.5 mL of 2.5 mol / L ferrous aminosulfonate solution, and perform reduction treatment for 30 minutes; add 0.5 mL of 4 mol / L sodium nitrite solution, and perform oxidation treatment for 10 minutes; adjust the valence states of plutonium isotopes and neptunium-237 in the sample to positive tetravalent;

[0049] Step 3, separation and purification: the sample solution obtained after the valence state adjustment in step 2 is passed through the pre-equilibrated TEVA resin column at a rate of 1 ml / min, and is sequentially eluted with 30 mL of 3 mol / L nitric acid solution and 30 mL of 9 mol / L hydrochloric acid solution, and desorbed with 0.36 mol / L hydrochloric acid-0.01 mol / L hydrofluoric acid solution at a flow rate of 0.2 mL / min at a temperature not lower than 20°C, and the desorbed liquid is collected; wherein, the pre-equilibration of the TEVA resin column uses a 3.0 mol / L nitric acid control solution to pre-equilibrate the TEVA resin column at a rate of 1 mL / min;

[0050] Step 4, electrodeposition source preparation: slowly evaporate the desorption solution collected in step 3, wash the small beaker with pH 2.2 ammonium sulfate solution three times, and transfer it to the electrodeposition tank with a dropper, place the electrodeposition tank in a flowing cold water bath, the distance between the electrodes is 10-15mm, and the current density is 900-1200mA / cm 2 Electrodeposition was performed for 2 hours. Ammonium hydroxide was added before termination, and the electrodeposition was continued for 3 minutes. The power was disconnected, the electrodeposition solution was discarded, and the plate was washed with water and ethanol in turn, and dried under an infrared lamp. The plate was placed in a low-background α spectrometer, and the radioactivity concentrations of plutonium-238, 239+240, and neptunium-237 were measured using plutonium-236 as a tracer.

[0051] Step 6, calculation: According to the alpha spectrometer counts of the tracer and the nuclide being tested and the known activity of the tracer, calculate the radioactivity concentrations of plutonium-238, 239+240 and neptunium-237 in the sample solution being tested. The calculation formula is as follows:

[0052]

[0053] Where:

[0054] A---Activity concentration of plutonium-238, 239+240 or neptunium-237 in the sample;

[0055] P---the count of plutonium-238, 239+240 or neptunium-237 in the sample;

[0056] E---Detection efficiency of the instrument;

[0057] Y---Full radiochemical recovery rate of plutonium-236;

[0058] V---the volume of the sample used, m 3 ;

[0059] The formula for calculating the whole-process radiochemical recovery rate of plutonium-236;

[0060]

[0061] Where:

[0062] N1---the activity of plutonium-236 in the sample source, Bq;

[0063] N0---The activity of plutonium-236 added to the sample, Bq.

[0064] In this example, three aerosol samples were measured and analyzed, and the measurement results are shown in Table 1;

[0065] Table 1

[0066]

[0067] The above-described embodiments are only preferred embodiments of the present invention, and are not exhaustive of the feasible implementations of the present invention. For those skilled in the art, any obvious changes made thereto without departing from the principles and spirit of the present invention should be considered to be included in the scope of protection of the claims of the present invention.

Claims

1. A method for the combined determination of plutonium-238, 239+240 and neptunium-237 in aerosols using Pu-236 as a yield tracer, characterized in that: The steps include: Step 1: Sample pretreatment: Cut the aerosol sample into pieces and add 236 Pu is used as an isotope tracer, and after ashing treatment, it is leached with nitric acid solution A to obtain a leaching solution; Step 2, valence adjustment: after adjusting the acidity of the leaching solution obtained in step 1, add hydroxylamine hydrochloride solution for reduction treatment, add ferrous aminosulfonate solution for further reduction treatment, and add sodium nitrite solution for oxidation treatment to adjust the valence state of the nuclide; Step 3, separation and purification: the sample solution obtained after adjusting the nuclide valence state in step 2 is separated and purified using a TEVA resin column, eluted with a nitric acid solution B and a hydrochloric acid solution, desorbed with an HCl-HF solution, and the desorbed liquid is collected; Step 4: Electrodeposit the desorption liquid collected in step 3 in an ammonium sulfate system to prepare a source, and then use a low-background alpha spectrometer to measure plutonium-238, 239+240 and neptunium-237, and calculate the radioactivity concentrations of plutonium-238, 239+240 and neptunium-237 in the sample solution according to the alpha spectrometer counts of the tracer and the nuclide being measured and the known activity of the tracer.

2. A method for the combined determination of plutonium-238, 239+240 and neptunium-237 in aerosols using Pu-236 as a yield tracer according to claim 1, characterized in that: In step 1, the leaching is performed twice, and the filtrates from the two times are combined to obtain an leaching solution; In step 1, the concentration of the nitric acid solution A used for leaching is 6-9 mol / L; In step 1, the ashing treatment is carried out in a muffle furnace at an ashing temperature of 600-700°C.

3. A method for the combined determination of plutonium-238, 239+240 and neptunium-237 in aerosols using Pu-236 as a yield tracer according to claim 1, characterized in that: In step 1, leaching is performed with nitric acid solution A, and reflux leaching is performed on a hot plate at 150-200°C.

4. A method for the combined determination of plutonium-238, 239+240 and neptunium-237 in aerosols using Pu-236 as a yield tracer according to claim 1, characterized in that: In step 2, the acidity of the leaching solution is adjusted to 3 mol / L; In step 2, the concentration of the hydroxylamine hydrochloride solution is 1-3 mol / L, and the reduction treatment time is 10-30 min; In step 2, the concentration of the ferrous sulfamate solution is 1-3 mol / L, and the further reduction treatment time is 10-30 min; In step 2, the concentration of the sodium nitrite solution is 3-5 mol / L, and the oxidation time is 10-30 min.

5. A method for the combined determination of plutonium-238, 239+240 and neptunium-237 in aerosols using Pu-236 as a yield tracer according to claim 1, characterized in that: In step 2, the valence states of plutonium-238, 239+240 and neptunium-237 in the sample are adjusted to be positive tetravalent.

6. A method for the combined determination of plutonium-238, 239+240 and neptunium-237 in aerosols using Pu-236 as a yield tracer according to claim 1, characterized in that: In step 2, the concentration of nitric acid solution B is 2-4 mol / L; the concentration of hydrochloric acid solution is 8-10 mol / L.

7. A method for the combined determination of plutonium-238, 239+240 and neptunium-237 in aerosols using Pu-236 as a yield tracer according to claim 1, characterized in that: In the HCl-HF solution, the concentration of HCl is 0.34-0.38 mol / L, and the concentration of HF is 0.008-0.012 mol / L.

8. A method for the combined determination of plutonium-238, 239+240 and neptunium-237 in aerosols using Pu-236 as a yield tracer according to claim 1, characterized in that: In step 5, the pH of the ammonium sulfate system is 2-3, and the current of the electrodeposition source is 900-1200 mA / cm 2 ; The electrodeposition time is 1.5-2.5h.

9. A method for the combined determination of plutonium-238, 239+240 and neptunium-237 in aerosols using Pu-236 as a yield tracer according to claim 1, characterized in that: Based on the alpha spectrometer counts of the tracer and the nuclide being tested and the known activity of the tracer, the calculation formula for calculating the radioactivity concentration of plutonium-238, 239+240 and neptunium-237 in the sample solution being tested is as follows: Where: A---Activity concentration of plutonium-238, 239+240 or neptunium-237 in the sample; N --- the count of plutonium-238, 239+240 or neptunium-237 in the sample; E---Detection efficiency of the instrument; Y---Full radiochemical recovery rate of plutonium-236; V---the volume of the sample used, m 3 .

10. A method for the combined determination of plutonium-238, 239+240 and neptunium-237 in aerosols using Pu-236 as a yield tracer according to claim 9, characterized in that: The formula for calculating the full radiochemical recovery rate of plutonium-236 is as follows; Where: N1---the activity of plutonium-236 in the sample source; Bq N0---the activity of plutonium-236 added to the sample; Bq.

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