CN112925005B - A method for determining the plutonium content of neptunium dioxide samples - Google Patents

Abstract

The method for measuring the plutonium content of the neptunium dioxide sample comprises the following steps of (1) preparing nitric acid hydrofluoric acid mixed acid solution; step (2) nitric acid solution; step (3) TOPO-xylene solution; step (4) sodium nitrite solution; step (5) preparation of plutonium standard discs; dissolving the sample in the step (6); diluting the solution in the step (7); step (8) extraction separation; step (9) sample preparation; step (10) sample measurement; the damage of the radioactivity of the sample to the operator is reduced, and the measurement error caused by the influence of americium element on the plutonium content measurement is eliminated. The analysis method for measuring the content of the plutonium in the neptunium can be used for measuring the content of the plutonium in neptunium products of power stack spent fuel post-treatment plants, the precision of the analysis method is better than 10%, and the labeling recovery rate is between 80% and 110%. The TOPO extraction and separation method has good separation effect of plutonium in neptunium, can meet the requirement of measuring the plutonium content in neptunium sample solution, and has the advantages of small interference of alpha energy spectrum measurement, few influence factors and good detection effect.

Description

A method for determining the plutonium content of neptunium dioxide samples

Technical field

The invention relates to the field of determination of plutonium content, and specifically relates to a method for determining the plutonium content of neptunium dioxide samples.

Background technique

With the rapid development of my country's aerospace industry, the demand for neptunium continues to increase, and the production of neptunium dioxide products also occurs accordingly. It is necessary to establish analysis and detection methods for each item in the corresponding neptunium dioxide products, and plutonium content is one of the items that must be tested. one. Therefore, it is very necessary to analyze the plutonium content in neptunium dioxide promptly and accurately.

The analysis methods for determining plutonium content include coulomb analysis, X-ray analysis, alpha counting method, etc. Among them, coulometric analysis and X-ray analysis can determine the plutonium content in solutions with high plutonium content. The plutonium content in neptunium dioxide is trace, so this method cannot be applied.

Since neptunium and plutonium have similar chemical properties and have alpha radioactivity, they cannot be completely separated after extraction and separation, so the results measured using the alpha counting method are on the high side. Measured using alpha energy spectroscopy, the energy of neptunium is at 4.8MeV and the energy of plutonium is at 5.5MeV. The element content of neptunium and plutonium can be measured simultaneously. The analysis data is accurate and reliable, and it can also meet the detection needs of process samples.

Contents of the invention

The purpose of the present invention is to study a method for the determination of trace amounts of plutonium in a large number of neptunium samples with a simple process and easy operation.

The technical solution of the present invention is as follows: a method for analyzing and determining the plutonium content of neptunium dioxide samples, including the following steps:

Step (1) Preparation of nitric acid hydrofluoric acid mixed acid solution;

Measure a certain volume of analytically pure nitric acid solution and add 10 mL to 20 mL of water while stirring. Then add a certain volume of analytically pure hydrofluoric acid solution. After cooling, transfer it to a volumetric flask and adjust to volume;

Step (2) nitric acid solution;

Take a certain volume of analytically pure nitric acid and place it in 20 mL to 30 mL of deionized water. After cooling to room temperature, transfer it to a volumetric flask and adjust to volume;

Step (3) TOPO-xylene solution;

Weigh a certain mass of analytically pure TOPO solid, dissolve it in 10 mL to 20 mL xylene, transfer it to a volumetric flask and dilute it to volume with xylene;

Step (4) sodium nitrite solution;

Weigh a certain mass of analytically pure sodium nitrite, dissolve it in 10 mL to 20 mL of deionized water, move it to a volumetric flask, and dilute to volume with deionized water;

Step (5) Preparation of plutonium standard disk;

Pipette 0.1 mL to 0.2 mL of plutonium solution with a known content into a small stainless steel plate, dry it, and measure and count on an alpha spectrometer;

Step (6) sample dissolution;

Weigh 10 mg ~ 40 mg neptunium dioxide sample into a 25 mL beaker; add 4 mL ~ 5 mL of the mixed acid solution of step (1), heat until the solution is completely dissolved, evaporate to nearly dryness, add 2 mL ~ 3 mL of 2 mol/L nitric acid solution (2), Volume;

Step (7) Solution dilution;

Pipette a certain volume of the sample solution in step (6) into another volumetric flask, and add 2 mol/L nitric acid solution in step (2) to adjust to volume;

Step (8) extraction and separation;

Pipette 1mL of the sample diluent from step (7) into the extraction tube, pipette a certain volume of the sodium nitrite solution from step (4), use a sampler to transfer 1mL of the TOPO solution prepared in step (3), and mix for 3 to 5 minutes. Centrifuge for another 1 minute and discard the water phase;

Step (9) sample plate making;

Transfer a certain volume of the organic phase solution from step (8) into a small dish, dry the small dish, dry it again, take it out and cool it to room temperature;

Step (10) Sample measurement;

Turn on the α spectrometer; measurement step (9) measure the α count (N ₁ ) of the sample plate on the α energy spectrometer, measure the stainless steel small plate without sample reagent in sequence, that is, the blank count (N _{0 ), and measure the standard plate count (N 0} ). N _b ), determine sample count (N ₁ );

Step (11) The plutonium content in the neptunium dioxide sample is calculated according to formula (1):

In the formula:

C——The measured plutonium content in neptunium dioxide, μgPu/gNpO ₂ ;

V ₀ ——The volume of the organic phase sample removed when making the plate, mL;

V ₁ ——volume of organic phase sample before extraction, mL;

V ₂ ——The volume of dissolved neptunium sample transferred during extraction, mL;

V ₃ ——The constant volume after the neptunium sample is dissolved, mL;

m _s ——Plutonium content in the standard disk, μg;

N _b ——count rate of plutonium in the standard disk;

N——count rate of plutonium in the sample pan;

N ₀ ——Blank disk count rate;

n——dilution factor of solution;

m——The so-called NpO ₂ product sample mass, mg.

In the step (1), deionized water is used to adjust the volume.

In the step (2), deionized water is used to adjust the volume.

In the step (3), a certain mass of analytically pure TOPO solid is weighed using an analytical balance of one ten thousandth or one hundred thousandth.

In the step (4), a certain mass of analytically pure sodium nitrite is weighed using an analytical balance of one ten thousandth or one hundred thousandth.

In the step (5), dry under infrared light.

In the step (6), place the heating plate on an electric hot plate.

In step (8), mix on a vortex mixer for 3 to 5 minutes, then put it into a low-speed desktop centrifuge and centrifuge for 1 minute, and discard the water phase.

In step (9), preheat for 30 minutes.

In the step (11), the data calculation is rounded in accordance with GB/T 8170, the results retain three significant figures, and are reported as the average of the two measurement results.

The significant effect of the present invention is that it reduces the harm caused by sample radioactivity to operators and eliminates the measurement error caused by the influence of americium element on the determination of plutonium content. The analytical method for the determination of plutonium content in neptunium established in this article can be used to determine the plutonium content in neptunium products in power reactor spent fuel reprocessing plants. The precision of the analytical method is better than 10%, and the recovery rate of standard addition is between 80% and 110%. . TOPO extraction and separation of plutonium in neptunium has a good separation effect, which can meet the requirements for the determination of plutonium content in neptunium sample solution. At the same time, alpha energy spectrum measurement has little interference, few influencing factors, and good detection results.

Detailed ways

Example 1

A method for analyzing and determining the plutonium content of neptunium dioxide samples, including the following steps:

(1) Preparation of nitric acid hydrofluoric acid mixed acid solution

Use a graduated cylinder to measure a certain volume of analytically pure nitric acid solution and add 10 mL to 20 mL of water while stirring. Then use a sampler to add a certain volume of analytically pure hydrofluoric acid solution. After cooling, transfer it to a volumetric flask and dilute it with deionized water.

(2) Nitric acid solution

Use a sampler to take a certain volume of analytically pure nitric acid and place it in 20 mL to 30 mL of deionized water. After cooling to room temperature, transfer it to a volumetric flask and make it up to volume with deionized water.

(3)TOPO-xylene solution

Weigh a certain mass of analytically pure TOPO solid using one ten thousandth or one hundred thousandth analytical balance, dissolve it in 10 mL to 20 mL xylene, transfer it to a volumetric flask and dilute it to volume with xylene.

(4)Sodium nitrite solution

Weigh a certain mass of analytically pure sodium nitrite using an analytical balance of one ten thousandth or one hundred thousandth, dissolve it in 10 mL to 20 mL deionized water, transfer it to a volumetric flask, and dilute it to volume with deionized water.

(5) Preparation of plutonium standard disk

Use a sampler to transfer 0.1 mL to 0.2 mL of plutonium solution with a known content into a small stainless steel plate, dry it under an infrared lamp, dry it on an electric stove, and measure and count on an alpha spectrometer.

(6) Sample dissolution

Use a 1/100,000 analytical balance to weigh 10 mg to 40 mg of neptunium dioxide sample into a 25 mL beaker. Add 4 mL to 5 mL of the mixed acid solution (1) above, place it on an electric hot plate and heat until the solution is completely dissolved, evaporate to nearly dryness, add 2 mL to 3 mL of 2 mol/L nitric acid solution (2), and transfer it to a volumetric flask to adjust to volume.

(7) Solution dilution

Use a sampler to transfer a certain volume of the above-mentioned sample solution (6) into another volumetric flask, and add 2 mol/L nitric acid solution (2) to adjust to volume.

(8) Extraction and separation

Use a sampler to transfer 1mL of sample diluent (7) into the extraction tube, use a sampler to transfer a certain volume of sodium nitrite solution (4), use a sampler to transfer 1mL of TOPO solution (3), and mix on a vortex mixer for 3 minutes. ~5min, then centrifuge in a low-speed desktop centrifuge for 1min, and discard the water phase.

(9) Sample plate making

Pipette a certain volume of organic phase solution (8) into a small stainless steel plate. Dry the small plate under an infrared lamp, then dry it on an adjustable electric stove at high temperature, then remove and cool to room temperature.

(10)Sample measurement

Turn on the alpha spectrometer and preheat for 30 minutes. The measuring source disk (9) measures the α count on the α energy spectrometer, and sequentially determines the blank count, standard count, and sample count.

(11) Calculate the plutonium content in the neptunium dioxide sample based on the measured counts

Example 2

A method for measuring plutonium content in neptunium dioxide samples. The specific measuring steps include the following steps:

(1) Preparation of nitric acid hydrofluoric acid mixed acid solution

Use a 100 mL graduated cylinder to measure 70 mL of analytical grade nitric acid solution into a 100 mL beaker containing 10 mL to 20 mL of deionized water. Then use a 1 mL adjustable sampler to add 0.3 mL of analytical grade hydrofluoric acid solution. After cooling to room temperature, transfer to 100 mL capacity. In the bottle, bring to volume with deionized water. The prepared nitric acid hydrofluoric acid mixed acid solution is 11 mol/L HNO ₃ -0.08 mol/L HF.

(2) Nitric acid

Use a 25 mL graduated cylinder to measure 15 mL of analytical grade nitric acid into a 100 mL beaker containing 20 mL to 30 mL of deionized water. After cooling to room temperature, transfer it to a 100 mL volumetric flask, and dilute to volume with deionized water. The concentration of the prepared nitric acid is 2.0 mol/ L～2.3mol/L.

(3)TOPO-xylene solution

Weigh 0.7328g of analytically pure TOPO using an analytical balance of one ten thousandth or one hundred thousandth, dissolve it in 10 mL to 20 mL xylene, transfer it to a 100 mL volumetric flask, and dilute it to volume with xylene. The concentration of the prepared TOPO solution is 0.18 mol/L～0.22mol/L.

(4)Sodium nitrite solution

Weigh 13.8g of analytically pure sodium nitrite using an analytical balance of one ten thousandth or one hundred thousandth, dissolve it in 10 mL to 20 mL deionized water, transfer it to a 100 mL volumetric flask, and dilute to volume with deionized water to prepare the nitrous acid The concentration of sodium solution is 1.9mol/L~2.1mol/L.

(5) Preparation of plutonium standard disk

Use a sampler to transfer 0.1 mL of plutonium solution with known content into a small stainless steel plate, dry it under a 250W infrared lamp and a 1000W adjustable electric furnace. The plutonium content on the plutonium standard plate used is generally 1.0×10 ^-7 mg～5.0×0 ^-7 mg.

(6) Sample dissolution

Use a 1/100,000 analytical balance to weigh 10 mg to 40 mg of neptunium dioxide sample into a 25 mL beaker. Add 4 mL to 5 mL of the above (1) mixed acid solution, place it on the electric hot plate at 170°C for 1 hour until the sample is completely dissolved, transfer it to a 10 mL volumetric flask and dilute it with deionized water.

(7) Solution dilution

Use a 1mL adjustable sampler to transfer 1mL of the above sample solution (6) into another 10mL volumetric flask, and add 2mol/L nitric acid solution to adjust to volume.

(8) Extraction and separation

Use a 1mL adjustable sampler to transfer 1mL of sample diluent (7) into a 5mL extraction tube, use a 0.1mL adjustable sampler to add 0.1mL sodium nitrite solution (4), and use a 1mL adjustable sampler to add 1mL of TOPO solution ( 3), mix on a 40W, 2400 rpm vortex mixer for 3 to 5 minutes, then put into a 10ml×6, 4000 rpm low-speed desktop centrifuge and centrifuge for 1 minute, and discard the water phase.

(9) Sample plate making

Pipette 0.2 mL of organic phase solution (8) into a small stainless steel plate. Dry the small plate under an infrared lamp, then dry it on an electric stove at high temperature, then remove and cool to room temperature.

(10) Determination

Turn on the alpha spectrometer and preheat for 30 minutes. The measuring source plate (9) measures the α count (N ₁ ) on the α energy spectrometer, and sequentially measures the stainless steel small plate without sample reagent, that is, the blank count (N ₀ ), measures the standard plate count (N _b ), and measures the sample count(N ₁ ).

(11) Result calculation

The plutonium content in the neptunium dioxide sample is calculated according to formula (1):

In the formula:

C——The measured plutonium content in neptunium dioxide, (μgPu/gNpO ₂ );

V ₀ ——The volume of the organic phase sample removed when making the plate, (mL);

V ₁ ——volume of organic phase sample before extraction, (mL);

V ₂ ——The volume of dissolved neptunium sample transferred during extraction, (mL);

V ₃ ——Constant volume after the neptunium sample is dissolved, (mL);

m _s ——Plutonium content in the standard disk, (μg);

N _b ——count rate of plutonium in the standard disk;

N——count rate of plutonium in the sample pan;

N ₀ ——Blank disk count rate;

n——dilution factor of solution;

m——The so-called NpO ₂ product sample mass, (mg).

Data calculations are rounded in accordance with GB/T 8170. The results retain three significant figures and are reported as the average of the two measurement results.

Claims (10)

1. A method for analyzing and determining the plutonium content of neptunium dioxide samples, which is characterized in that: it includes the following steps: Step (1) Preparation of nitric acid hydrofluoric acid mixed acid solution; Measure a certain volume of analytically pure nitric acid solution and add 10 mL to 20 mL of water while stirring. Then add a certain volume of analytically pure hydrofluoric acid solution. After cooling, transfer it to a volumetric flask and adjust to volume; Step (2) nitric acid solution; Take a certain volume of analytically pure nitric acid and place it in 20 mL to 30 mL of deionized water. After cooling to room temperature, transfer it to a volumetric flask and adjust to volume; Step (3) TOPO-xylene solution; Weigh a certain mass of analytically pure TOPO solid, dissolve it in 10 mL to 20 mL xylene, transfer it to a volumetric flask and dilute it to volume with xylene; Step (4) sodium nitrite solution; Weigh a certain mass of analytically pure sodium nitrite, dissolve it in 10 mL to 20 mL of deionized water, move it to a volumetric flask, and dilute to volume with deionized water; Step (5) Preparation of plutonium standard disk; Pipette 0.1 mL to 0.2 mL of plutonium solution with a known content into a small stainless steel plate, dry it, and measure and count on an alpha spectrometer; Step (6) sample dissolution; Weigh 10mg ~ 40mg neptunium dioxide sample into a 25mL beaker; add 4mL ~ 5mL of the mixed acid solution in step (1), heat until the solution is completely dissolved, evaporate to nearly dryness, add 2mL ~ 3mL, 2mol/L step (2) nitric acid solution; Step (7) Solution dilution; Pipette a certain volume of the sample solution in step (6) into another volumetric flask, and add 2 mol/L nitric acid solution in step (2) to adjust to volume; Step (8) extraction and separation; Pipette 1mL of the sample diluent from step (7) into the extraction tube, pipette a certain volume of the sodium nitrite solution from step (4), use a sampler to transfer 1mL of the TOPO solution prepared in step (3), and mix for 3 to 5 minutes. Centrifuge for another 1 minute and discard the water phase; Step (9) sample plate making; Transfer a certain volume of the organic phase solution from step (8) into a small dish, dry the small dish, dry it again, take it out and cool it to room temperature; Step (10) Sample measurement; Turn on the α spectrometer; measurement step (9) measure the α count N ₁ of the sample plate on the α energy spectrometer, and measure the stainless steel small plate without sample reagent in sequence, that is, the blank count N ₀ , measure the standard plate meter N _b , and measure the sample count N ₁ ; Step (11) The plutonium content in the neptunium dioxide sample is calculated according to formula (1): In the formula: C——The measured plutonium content in neptunium dioxide, μgPu/gNpO ₂ ; V ₀ ——The volume of the organic phase sample removed when making the plate, mL; V ₁ ——volume of organic phase sample before extraction, mL; V ₂ ——The volume of dissolved neptunium sample transferred during extraction, mL; V ₃ ——The constant volume after the neptunium sample is dissolved, mL; m _s ——Plutonium content in the standard disk, μg; N _b ——count rate of plutonium in the standard disk; N——count rate of plutonium in the sample pan; N ₀ ——Blank disk count rate; n——dilution factor of solution; m——The so-called NpO ₂ product sample mass, mg. 2. A method for analyzing and determining the plutonium content of a neptunium dioxide sample according to claim 1, characterized in that: in the step (1), deionized water is used to set the volume. 3. A method for analyzing and determining the plutonium content of neptunium dioxide samples according to claim 1, characterized in that: in the step (2), deionized water is used to adjust the volume. 4. A method for analyzing and determining the plutonium content of a neptunium dioxide sample according to claim 1, characterized in that: in the step (3), a certain amount is weighed using an analytical balance of one ten thousandth or one hundred thousandth. Mass analysis of pure TOPO solid. 5. A method for analyzing and determining the plutonium content of a neptunium dioxide sample according to claim 1, characterized in that: in the step (4), a certain amount is weighed using an analytical balance of one ten thousandth or one hundred thousandth. Quality analysis of pure sodium nitrite. 6. A method for analyzing and determining the plutonium content of a neptunium dioxide sample according to claim 1, characterized in that: in the step (5), the sample is dried under an infrared lamp. 7. A method for analyzing and determining the plutonium content of neptunium dioxide samples according to claim 1, characterized in that: in the step (6), an electric heating plate is placed for heating. 8. A method for analyzing and determining the plutonium content of a neptunium dioxide sample according to claim 1, characterized in that: in the step (8), mix on a vortex mixer for 3min to 5min, and then put into a low-speed desktop centrifuge Centrifuge for 1 min and discard the water phase. 9. A method for analyzing and determining the plutonium content of neptunium dioxide samples according to claim 1, characterized in that: in the step (9), preheating is performed for 30 minutes. 10. A method for analyzing and determining the plutonium content of a neptunium dioxide sample according to claim 1, characterized in that: in the step (11), the data calculation is rounded according to GB/T 8170, and the result remains valid for three digits. Numbers are reported as the average of two measurement results.