Method for combined determination of 241Am and 244Cm in aerosol by taking 243Am as yield tracer

Abstract

The invention relates to a method for jointly determining 241Am and 244Cm in aerosol by taking 243Am as a yield tracer, which comprises the following steps: step 1, sample pretreatment: cutting an aerosol sample into pieces, adding 243Am as an isotopic tracer, ashing, and leaching by adopting a nitric acid solution A; 2, valence state adjustment, wherein a ferrous sulfamate solution is sequentially added into the leaching solution for reduction treatment, and a sodium nitrite solution is added for oxidation treatment; step 3, precipitating calcium oxalate: sequentially adding oxalic acid and calcium chloride into the sample solution, adjusting the pH value to 2.0, collecting the precipitate, and firing; step 4, separation and purification: dissolving the sample with a nitric acid solution B, and then separating and purifying with a DGA resin column; and step 5, carrying out electro-deposition on the eluent in an ammonium sulfate system to prepare a source, and carrying out measurement of 241Am and 244Cm by adopting a low background alpha spectrometer. According to the method, interference of fission elements such as plutonium isotope is low, and the recovery rate of curium-244 is high.

Description

Technical Field

[0001] The present invention belongs to the technical field of radioactive material detection, and specifically relates to a method for 243 Am as a yield tracer for the combined determination of 241 Am and 244 The method of Cm. Background Art

[0002] With the increasingly stringent requirements for national environmental protection, the continuous strengthening of public environmental awareness and the implementation of energy conservation and emission reduction policies, it is of great significance to improve the level of relevant analysis technology and ensure that relevant units can better complete environmental monitoring and evaluation work.

[0003] Americium (Am) and curium (Cm) are two key transuranium actinide elements. The most common isotope of americium with the longest half-life is 241 Am and 243 Am, with half-lives of 432.2 and 7,370 years respectively; curium is mainly produced by neutron radiation of uranium and / or plutonium oxides in nuclear reactors; there are more than 20 known isotopes of curium, with mass numbers between 232 and 252. All isotopes are radioactive and are mainly alpha particle emitters. The isotopes curium-242 and curium-244 (with half-lives of 163 days and 18.1 years respectively) account for 90% of the total curium produced in the nuclear fuel cycle. Americium (Am) and curium (Cm) are potentially extremely harmful to the environment. Therefore, it is extremely important to detect and analyze the nuclides americium (Am) and curium (Cm). Joint analysis has the advantages of low workload and high detection efficiency and is widely used in the detection of pollutants. However, in alpha spectrum measurement, 238 The α spectrum peak of Pu 241 The α spectrum peaks of Am overlap, resulting in 241 Am and 238 The α energy spectrum peaks of Pu interfere with each other. To ensure that they do not affect the analysis results, it is crucial to remove fission elements such as plutonium isotopes. At the same time, americium (Am) and curium (Cm) have similar chemical properties. The isotope of curium-244 is a short-lived nuclide with a short half-life (163d). It is not easy to obtain and preserve, and its application is relatively small. How to determine the recovery rate of curium-244 in the sample is also a very critical research content in its detection. Therefore, it is necessary to develop a detection method with low interference from fission elements such as plutonium isotopes and high recovery rate of curium-244 for use in aerosols. 241 Am and 244 The joint analysis of Cm is crucial. Summary of the invention

[0004] The purpose of the present invention is to overcome the defects in the prior art and provide a 243 Am as a yield tracer for the combined determination of 241 Am and244 The Cm method has low interference from fission elements such as plutonium isotopes and a high recovery rate of curium-244.

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

[0006] A 243 Am as a yield tracer for the combined determination of 241 Am and 244 The method of Cm comprises the following steps:

[0007] Step 1: Sample pretreatment: Cut the aerosol sample into pieces and add 243 Am 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: adding ferrous sulfamate solution to the leaching solution obtained in step 1 for reduction treatment and sodium nitrite solution for oxidation treatment in order to adjust the valence of the nuclide;

[0009] Step 3, calcium oxalate precipitation: add oxalic acid and calcium chloride to the sample solution after adjusting the nuclide valence in step 2, and add deionized water to adjust the solution pH to 2.0, then collect the precipitate, and burn the precipitate;

[0010] Step 4, separation and purification: dissolving the sample obtained by the burning treatment in step 3 with nitric acid solution B, and then separating and purifying it with a DGA resin column, eluting it with nitric acid solution C and hydrochloric acid solution, eluting it with dilute hydrochloric acid solution, and collecting the eluate;

[0011] Step 5: Electrodeposit the eluate collected in step 4 in an ammonium sulfate system to prepare a source, and then use a low-background α spectrometer to analyze the 241 Am and 244 The measurement of Cm and the calculation of the amount of Cm in the sample solution are based on the α spectrometer counts of the tracer and the nuclide being measured and the known activity of the tracer. 241 Am and 244 The radioactivity concentration of Cm.

[0012] As a further technical solution, in step 1, the leaching is performed twice, and the two filtrates are combined to obtain an leaching solution;

[0013] 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).

[0014] As a further technical solution, in step 1, the ashing treatment is carried out in a muffle furnace, and the ashing treatment temperature is 600-700° C. (preferably 650° C.).

[0015] As a further technical solution, during the leaching of the nitric acid solution A, reflux leaching is performed on a hot plate at 150-200° C. (preferably 170° C.);

[0016] 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 10-40 min (preferably 30 min);

[0017] As a further technical solution, in step 2, the concentration of the sodium nitrite solution is 3-5 mol / L (preferably 4.0 mol / L), and the oxidation time is 10-40 min (preferably 30 min).

[0018] As a further technical solution, in step 3, the calcination treatment is carried out in a muffle furnace, and the temperature of the calcination treatment is 600-700° C. (preferably 650° C.).

[0019] As a further technical solution, in step 3, the concentration of the nitric acid solution B is 2-4 mol / L (preferably 3.0 mol / L);

[0020] As a further technical solution, in step 4, the concentration of nitric acid solution C 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); and the concentration of dilute hydrochloric acid solution is 0.05-0.15 mol / L (preferably 0.1 mol / L).

[0021] As a further technical solution, in step 5, the current of the electrodeposition source is 900-1200 mA / cm 2 ; The electrodeposition time is 1.5-2.5h.

[0022] As a further technical solution, the α spectrometer counts of the tracer and the nuclide to be measured and the known activity of the tracer are used to calculate the concentration of the nuclide in the sample solution to be measured. 241 Am and 244 The calculation formula of Cm radioactivity concentration is as follows:

[0023]

[0024] Where:

[0025] B---Activity concentration of americium-241 or curium-244 in the sample;

[0026] O---Count of americium-241 or curium-244237 in the sample;

[0027] E---Detection efficiency of the instrument;

[0028] Y---the whole radiochemical recovery rate of americium-243;

[0029] V---the volume of the sample used, m 3 .

[0030] As a further technical solution, the whole process radiochemical recovery rate of americium-243 is calculated as follows:

[0031]

[0032] Where:

[0033] N1---Activity of americium-243 in the sample source, Bq;

[0034] N0---Activity of americium-243 added to the sample, Bq.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] The present invention is the first to adopt 243 Am as a yield tracer for the determination of 241 Am and 244 The combined analysis method of Cm can adjust the valence state of fission elements such as plutonium isotopes and neptunium isotopes in the sample to positive tetravalent, positive pentavalent or other valence states, so as to achieve the separation of americium and curium and fission elements. 243 Am is used as a yield tracer to simultaneously trace the recovery of americium-241 and curium-244. The present invention actually analyzes americium-243 as an "isotope" of curium-244; and uses americium-243 as a recovery tracer in the separation process of americium-241 and curium-244. The operation is simple and can be used as 241 Am and 244 Combined analysis of Cm by conventional laboratory analysis method. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 In one embodiment of the present invention, 243 Am as a yield tracer for the combined determination of 241 Am and 244 Flowchart of the method of Cm. DETAILED DESCRIPTION

[0038] 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.

[0039] In the present invention,

[0040] Aerosol samples: collected in a certain place in my country, the sampling instrument is Anderson sampler, 50L / min flow rate, to obtain the tested samples;

[0041] Unless otherwise specified, the raw materials used in the present invention are commercially available.

[0042] Example 1

[0043] A 243 Am as a yield tracer for the combined determination of 241 Am and 244 The method of Cm comprises the following steps:

[0044] Step 1: Sample pretreatment: Cut the aerosol sample into pieces and add 243 Am (activity of standard solution: 0.099528 Bq / ml, after correction) was used as an isotope tracer. After ashing treatment at 650°C in a muffle furnace, 7.5 mol / L nitric acid solution was added and reflux leaching was performed twice on a 170°C hot plate, with 30 mL of 7.5 mol / L nitric acid solution added each time, and the extracts were combined.

[0045] Step 2, valence state adjustment: add 0.5 mL of 2.5 mol / L ferrous aminosulfonate solution to the leaching solution obtained in step 1, and perform reduction treatment for 30 min; add 0.5 mL of 4.0 mol / L sodium nitrite solution, and perform oxidation treatment for 30 min; adjust the valence state of nuclides such as plutonium isotopes and neptunium isotopes in the sample to positive tetravalent, positive pentavalent or other valence states to avoid affecting the separation and purification of americium and curium;

[0046] Step 3, calcium oxalate precipitation: add 1.0 g of oxalic acid to the sample solution after adjusting the nuclide valence state in step 2, dissolve for 10 min, add 0.2 g of calcium chloride, shake for 30 min, add 2.0 mol / L sodium hydroxide solution to adjust the solution pH to 2.0, then collect the precipitate, and place the precipitate in a muffle furnace and burn it at 650° C. for 6 h;

[0047] Step 4, separation and purification: add 50 mL of 3.0 mol / L nitric acid solution to the sample obtained by the calcination treatment in step 3 to dissolve the sample, then pass it through the pre-equilibrated DGA resin column at a speed of 1 ml / min, and wash it with 50 mL of 3 mol / L nitric acid solution and 50 mL of 9 mol / L hydrochloric acid solution in sequence, and elute it with 50 mL of 0.1 mol / L dilute hydrochloric acid solution, and collect the eluate;

[0048] The DGA resin column was pre-equilibrated with a 3.0 mol / L nitric acid solution, and the flow rate of the 3.0 mol / L nitric acid solution was 1.0 ml / min;

[0049] Step 5, electrodeposition source preparation: The eluate collected in step 4 is electrodeposited in an ammonium sulfate system at pH 2.2 to prepare a source, and then a low-background α spectrometer is used for 241 Am and 244 Measurement of Cm,

[0050] The specific operation of the electrodeposition source is as follows: the platinum wire is connected to the positive electrode, the electroplating sheet is connected to the cathode, and the current density is controlled to 800-1200mA / cm 2 After electroplating for 1 hour and 50 minutes, add 2-3 ml of concentrated ammonia water and continue electroplating for 5 minutes. Take out the electroplated sheet, wash it with deionized water and ethanol in turn, and dry it under an infrared lamp;

[0051] Step 6: Calculate: Based on the α spectrometer counts of the tracer and the nuclide being tested and the known activity of the tracer, calculate the 241 Am and 244 The radioactivity concentration of Cm is calculated as follows:

[0052]

[0053] Where:

[0054] C---activity concentration of americium-241 or curium-244 in the sample;

[0055] P---Count of americium-241 or curium-244237 in the sample;

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

[0057] Y---the whole radiochemical recovery rate of americium-243;

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

[0059] The calculation formula of the whole radiochemical recovery rate of americium-243;

[0060]

[0061] Where:

[0062] N1---Activity of americium-243 in the sample source, Bq;

[0063] N0 --- the activity of americium-243 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 243 Am as a yield tracer for the combined determination of 241 Am and 244 Cm method, characterized in that The steps include: Step 1: Sample pretreatment: Cut the aerosol sample into pieces and add 243 Am 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: adding ferrous sulfamate solution to the leaching solution obtained in step 1 for reduction treatment and sodium nitrite solution for oxidation treatment in order to adjust the valence of the nuclide; Step 3, calcium oxalate precipitation: add oxalic acid and calcium chloride to the sample solution after adjusting the nuclide valence in step 2, and adjust the solution pH to 2.0, then collect the precipitate, and burn the precipitate; Step 4, separation and purification: dissolving the sample obtained by the burning treatment in step 3 with nitric acid solution B, and then separating and purifying it with a DGA resin column, eluting it with nitric acid solution C and hydrochloric acid solution, eluting it with dilute hydrochloric acid solution, and collecting the eluate; Step 5: Electrodeposit the eluate collected in step 4 in an ammonium sulfate system to prepare a source, and then use a low-background α spectrometer to analyze the 241 Am and 244 The measurement of Cm and the calculation of the amount of Cm in the sample solution are based on the α spectrometer counts of the tracer and the nuclide being measured and the known activity of the tracer. 241 Am and 244 The radioactivity concentration of Cm.

2. A method according to claim 1 243 Am as a yield tracer for the combined determination of 241 Am and 244 Cm method, characterized in that In step 1, the leaching is performed twice, and the two filtrates 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.

3. A method according to claim 1 243 Am as a yield tracer for the combined determination of 241 Am and 244 Cm method, characterized in that In step 1, the ashing treatment is carried out in a muffle furnace at a temperature of 600-700°C.

4. A method according to claim 1 243 Am as a yield tracer for the combined determination of 241 Am and 244 Cm method, characterized in that In step 2, the concentration of the ferrous sulfamate solution is 1-3 mol / L, and the reduction time is 10-40 min; The concentration of the sodium nitrite solution is 3-5 mol / L, and the oxidation time is 10-40 min.

5. A method according to claim 1 243 Am as a yield tracer for the combined determination of 241 Am and 244 Cm method, characterized in that In step 3, the calcination treatment is carried out in a muffle furnace at a temperature of 600-700°C.

6. A method according to claim 1 243 Am as a yield tracer for the combined determination of 241 Am and 244 Cm method, characterized in that The concentration of the nitric acid solution B is 2-4 mol / L.

7. A method according to claim 1 243 Am as a yield tracer for the combined determination of 241 Am and 244 Cm method, characterized in that In step 4, the concentration of nitric acid solution C is 2-4 mol / L; the concentration of hydrochloric acid solution is 8-10 mol / L; and the concentration of dilute hydrochloric acid solution is 0.1 mol / L.

8. A method according to claim 1 243 Am as a yield tracer for the combined determination of 241 Am and 244 Cm method, characterized in that In step 5, the current of the electrodeposition source is 900-1200 mA / cm 2 ; The electrodeposition time is 1.5-2.5h.

9. A method according to claim 1 243 Am as a yield tracer for the combined determination of 241 Am and 244 Cm method, characterized in that According to the α spectrometer counts of the tracer and the nuclide being tested and the known activity of the tracer, calculate the 241 Am and 244 The calculation formula of Cm radioactivity concentration is as follows: Where: A---Activity concentration of americium-241 or curium-244 in the sample; N---the count of americium-241 or curium-244237 in the sample; E---Detection efficiency of the instrument; Y---the whole radiochemical recovery rate of americium-243; V---the volume of the sample used, m 3 .

10. A method according to claim 9 243 Am as a yield tracer for the combined determination of 241 Am and 244 Cm method, characterized in that The calculation formula for the whole process radiochemical recovery rate of americium-243 is as follows; Where: N1---Activity of americium-243 in the sample source, Bq; N0---Activity of americium-243 added to the sample, Bq.

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