1. The method for analyzing the content of uranium isotopes in calcium fluoride slag is characterized by comprising the following steps:

(1) adding a certain activity to the tested calcium fluoride slag sample²³²U is used as a tracer, then nitric acid is added for soaking, heating and evaporation are carried out until the solution is nearly dry, the same nitric acid is added, and the solution is evaporated until the solution is nearly dry for several times;

(2) adding hydrochloric acid, heating to dissolve the sample, and cooling to room temperature;

(3) loading the sample on an anion exchange resin column, and desorbing uranium by using nitric acid;

(4) and (3) carrying out evaporation by adding sulfuric acid, adjusting the pH value by ammonia water, carrying out electrodeposition by plating, then, placing the stripping solution on an alpha spectrometer for measurement, and calculating the content of uranium isotopes in the sample.

2. The analytical method of claim 1, wherein: in the step (1), the²³²The activity of U is 0.03-1.0 Bq.

3. The analytical method of claim 1, wherein: in the step (1), the concentration of the nitric acid added each time is 4-15 mol/L, and the volume is 25-200 mL.

4. The analytical method of claim 1, wherein: in the step (1), the evaporation to near dryness is to remove 80-95% of water by evaporation.

5. The analytical method of claim 1, wherein: in the step (2), the concentration of the added hydrochloric acid is 6-12 mol/L, and the volume is 25-100 mL.

6. The analytical method of claim 1, wherein: in the step (3), the concentration of the nitric acid is 0.01-0.3 mol/L.

7. The analytical method of claim 1, wherein: in the step (4), the pH value of the ammonia water is adjusted to 1-3.

8. The analytical method of claim 1, wherein: in the step (4), the current density of the electrodeposition is 500-²The time is 0.5h-3 h.

9. The analytical method of claim 1, wherein: in the step (4), the content of the uranium isotope in the sample is calculated according to the tracer²³²Alpha spectrometer counting of U and detected nuclide, and tracer²³²U known activity, calculating in the measured sample²³⁸U、²³⁴U、²³⁵Activity concentration of U.

10. The analytical method of claim 9, wherein:

²³⁸the formula for calculating the activity concentration of U is:

wherein:

A_238U: in calcium fluoride slag sample to be measured²³⁸U activity concentration, unit Bq/g;

A_232U: tracer agent²³²U addition, unit: bq;

N_238U: on the plated sheet²³⁸Counting of U;

N_232U: on the plated sheet²³²Counting of U;

e: detecting efficiency;

y: recovery rate;

m: the weight of the calcium fluoride slag, unit g,

²³⁴the formula for calculating the activity concentration of U is:

wherein:

A_234U: in calcium fluoride slag sample to be measured²³⁴U activity concentration, unit Bq/g;

A_232U: tracer agent²³²U addition, unit: bq;

N_234U: on the plated sheet²³⁴Counting of U;

N_232U: on the plated sheet²³²Counting of U;

e: detecting efficiency;

y: recovery rate;

m: the weight of the calcium fluoride slag, unit g,

²³⁵the formula for calculating the activity concentration of U is:

wherein:

A_235U: in calcium fluoride slag sample to be measured²³⁵U activity concentration, unit Bq/g;

A_232U: tracer agent²³²U addition, unit: bq;

N_235U: on the plated sheet²³⁵Counting of U;

N_232U: on the plated sheet²³²Counting of U;

e: detecting efficiency;

y: recovery rate;

m: weight of calcium fluoride slag in g.

Background

In recent years, with the higher and higher requirements of national environmental protection, the continuous strengthening of public environmental protection consciousness and the implementation of energy-saving and emission-reducing policies, higher requirements are put forward on waste management and emission of nuclear facilities. Uranium-bearing waste water that produces in the uranium enrichment process is handled through lime milk sedimentation method, and the waste water after the processing can realize discharge to reach standard, and the uranium isotope in the waste water is concentrated to in the calcium fluoride sediment. The lime milk precipitation method is a cheap and effective method, and is widely applied to uranium-containing wastewater treatment by domestic uranium concentration plants in decades. Over time, however, uranium concentration plants accumulate large amounts of calcium fluoride slag.

According to the radioactive waste related laws and standards, the accumulated calcium fluoride slag must be disposed of as soon as possible, and the calcium fluoride slag is classified, managed and disposed according to the specific activity of radioactivity based on the waste minimization principle. However, at present, no standard method for analyzing uranium isotopes in calcium fluoride slag exists in China, the uranium isotopes in the calcium fluoride slag are difficult to analyze, many units do not have accurate and reliable analysis means, and the rapid development of waste management in uranium enrichment is restricted to a certain extent.

The uranium isotope in the calcium fluoride slag has high analysis difficulty mainly because: (1) the main component of the calcium fluoride slag is calcium fluoride, uranium isotope analysis in the calcium fluoride firstly needs to leach uranium isotope out of the calcium fluoride, and the uranium isotope is converted into liquid solution for nuclide separation and purification and radioactive measurement, but the calcium fluoride contains F^1-Ions and samples are difficult to dissolve, so that great difficulty is brought to analysis work; (2) the separation and purification requirements of uranium isotopes are high, and nuclides which influence the measurement of an alpha spectrometer and are close to the energy of the uranium isotopes and some major elements must be removed completely in the separation process of the upper column.

Therefore, from the perspective of waste minimization principle and classification management, it is very necessary to establish an analysis method for uranium isotope content in calcium fluoride slag to fill up the technical gap in the aspect, ensure that relevant units can better complete waste monitoring and management work, provide technical support for environmental protection supervision, and promote more healthy and orderly development of uranium concentration industry.

Disclosure of Invention

The invention aims to provide an analysis method of uranium isotope content in calcium fluoride slag, so that the uranium isotope content in the calcium fluoride slag can be accurately and reliably analyzed.

To achieve this object, in a basic embodiment, the present invention provides a method for analyzing the uranium isotope content in calcium fluoride slag, the method comprising the steps of:

(1) adding a certain activity to the tested calcium fluoride slag sample²³²U is used as a tracer, then nitric acid is added for soaking, heating and evaporation are carried out until the solution is nearly dry, the same nitric acid is added, and the solution is evaporated until the solution is nearly dry for several times;

(2) adding hydrochloric acid, heating to dissolve the sample, and cooling to room temperature;

(3) loading the sample on an anion exchange resin column, and desorbing uranium by using nitric acid;

(4) and (3) carrying out evaporation by adding sulfuric acid, adjusting the pH value by ammonia water, carrying out electrodeposition by plating, then, placing the stripping solution on an alpha spectrometer for measurement, and calculating the content of uranium isotopes in the sample.

In a preferred embodiment, the invention provides a method for analyzing the content of uranium isotopes in calcium fluoride slag, wherein in step (1), the method is used for analyzing the content of uranium isotopes in calcium fluoride slag²³²The activity of U is 0.03-1.0 Bq.

In a preferred embodiment, the invention provides a method for analyzing the content of uranium isotopes in calcium fluoride slag, wherein in the step (1), the concentration of nitric acid added each time is 4-15 mol/L, and the volume is 25-200 mL.

In a preferred embodiment, the invention provides a method for analyzing the uranium isotope content in calcium fluoride slag, wherein in the step (1), the evaporation to near dryness is to remove 80-95% of water by evaporation.

In a preferred embodiment, the invention provides a method for analyzing the content of uranium isotopes in calcium fluoride slag, wherein in the step (2), the hydrochloric acid is added in a concentration of 6mol/L-12mol/L and a volume of 25-100 mL.

In a preferred embodiment, the invention provides a method for analyzing the content of uranium isotopes in calcium fluoride slag, wherein in the step (3), the concentration of the nitric acid is 0.01mol/L-0.3 mol/L.

In a preferred embodiment, the invention provides a method for analyzing the content of uranium isotopes in calcium fluoride slag, wherein in the step (4), the ammonia water is used for adjusting the pH to 1-3.

In a preferred embodiment, the invention provides a method for analyzing the uranium isotope content in calcium fluoride slag, wherein in the step (4), the current density of electrodeposition is 500-1200mA/cm²The time is 0.5h-3 h.

In a preferred embodiment, the invention provides a method for analyzing the content of uranium isotopes in calcium fluoride slag, wherein in step (4), the content of uranium isotopes in the sample is calculated according to a tracer²³²Alpha spectrometer counting of U and detected nuclide, and tracer²³²U known activity, calculating in the measured sample²³⁸U、²³⁴U、²³⁵Activity concentration of U.

In a more preferred embodiment, the present invention provides a method for analyzing the uranium isotope content in calcium fluoride slag, wherein:

²³⁸the formula for calculating the activity concentration of U is:

wherein:

A_238U: in calcium fluoride slag sample to be measured²³⁸U activity concentration, unit Bq/g;

A_232U: tracer agent²³²U addition, unit: bq;

N_238U: on the plated sheet²³⁸Counting of U;

N_232U: on the plated sheet²³²Counting of U;

e: detecting efficiency;

y: recovery rate;

m: the weight of the calcium fluoride slag, unit g,

²³⁴the formula for calculating the activity concentration of U is:

wherein:

A_234U: in calcium fluoride slag sample to be measured²³⁴U activity concentration, unit Bq/g;

A_232U: tracer agent²³²U addition, unit: bq;

N_234U: on the plated sheet²³⁴Counting of U;

N_232U: on the plated sheet²³²Counting of U;

e: detecting efficiency;

y: recovery rate;

m: the weight of the calcium fluoride slag, unit g,

²³⁵the formula for calculating the activity concentration of U is:

wherein:

A_235U: in calcium fluoride slag sample to be measured²³⁵U activity concentration, unit Bq/g;

A_232U: tracer agent²³²U addition, unit: bq;

N_235U: on the plated sheet²³⁵Counting of U;

N_232U: on the plated sheet²³²Counting of U;

e: detecting efficiency;

y: recovery rate;

m: weight of calcium fluoride slag in g.

The method has the beneficial effects that the method for analyzing the content of the uranium isotope in the calcium fluoride slag can accurately and reliably analyze the content of the uranium isotope in the calcium fluoride slag.

Drawings

Fig. 1 is a flow chart illustrating an exemplary method for analyzing the uranium isotope content in calcium fluoride slag according to the present invention.

Fig. 2 is an alpha spectrum of uranium isotope measurement in a calcium fluoride slag sample in example 1.

Detailed Description

The following description will further describe embodiments of the present invention with reference to the accompanying drawings.

Example 1:

an exemplary method for analyzing the uranium isotope content in calcium fluoride slag according to the present invention has a flow chart as shown in fig. 1, and includes the following steps:

(1) accurately weighing 2g of calcium fluoride slag samples (9 samples from a certain place in China) in a polytetrafluoroethylene beaker;

(2) into the tested sampleAdding 0.08Bq²³²U is used as a tracer;

(3) adding 50mL of 7.5mol/L nitric acid into a sample to be detected, and soaking overnight;

(4) heating and evaporating on an electric heating plate until the temperature is nearly dry, and cooling to room temperature;

(5) repeating the steps (3) and (4) twice;

(6) adding 50mL of 9mol/L hydrochloric acid into the sample obtained in the step (5), heating to dissolve, and cooling to room temperature;

(7) passing 9mol/L nitric acid through an anion exchange column (type 205 anion exchange resin, bed height 15cm, diameter 1 cm);

(8) enabling the sample solution obtained in the step (6) to pass through an ion exchange column at the flow rate of 1 mL/min;

(9) eluting the column with 6 × 20mL of 9mol/L hydrochloric acid, and discarding the effluent;

(10) eluting the column with 8mol/L ammonium nitrate-0.1M nitric acid mixed solution until iron is eluted, placing a small beaker at the lower end of the column to collect eluate, and dropwise adding ammonium hydrogen sulfate into the eluate until no iron is detected;

(11) desorbing U in the column by using 0.1mol/L nitric acid, and collecting about 70mL of desorption solution by using a beaker;

(12) adding 1mL of concentrated sulfuric acid (18mol/L) into the desorption solution obtained in the step (11), placing on an electric hot plate, heating and steaming until white smoke is exhausted, taking down and cooling to room temperature, adding ammonia water to adjust the pH value to be about 2.2, transferring to an electrodeposition device, washing the beaker containing the original sample with a solution with the pH value of 2.2 for three times, transferring the washing solution to the electrodeposition device, and controlling the total volume to be 20-25 mL. Putting the electrodeposition device in a cold water bath, connecting a power supply and heating at 500-²And (4) electrodeposition (0.5h-3h) at the current density of (1). Adding 1mL of concentrated ammonia water (with mass percent concentration of 50-28%) into an electrodeposition device, continuing electrodeposition for 1min, cutting off a power supply, removing electrodeposition liquid, washing a plated sheet with distilled water and absolute ethyl alcohol in sequence, drying under an infrared lamp, and measuring on a low-background alpha spectrometer;

(13) calculation of the content of the U isotope in the tested sample: according to the tracer²³²Counting and tracing agent for U and detected nuclide²³²Known activity of UCalculating the measured sample²³⁸U、²³⁴U、²³⁵Activity concentration of U. The method comprises the following specific steps:

1)²³⁸activity concentration of U: according to²³⁸U and²³²u count ratio sum²³²U activity, calculating in the measured sample²³⁸U activity concentration, and the calculation formula is shown as formula (1):

wherein:

A_238U: in calcium fluoride slag sample to be measured²³⁸U activity concentration, unit Bq/g;

A_232U: tracer agent²³²U addition, unit: bq;

N_238U: on the plated sheet²³⁸Counting of U;

N_232U: on the plated sheet²³²Counting of U;

e: detecting efficiency;

y: recovery rate;

m: calcium fluoride slag volume in g.

2)²³⁴Activity concentration of U: according to²³⁴U and²³²u count ratio sum²³²U activity, calculating in the measured sample²³⁴U activity concentration, and the calculation formula is shown as formula (2):

wherein:

A_234U: in calcium fluoride slag sample to be measured²³⁴U activity concentration, unit Bq/g;

A_232U: tracer agent²³²U addition, unit: bq;

N_234U: on the plated sheet²³⁴Counting of U;

N_232U: on the plated sheet²³²Counting of U;

e: detecting efficiency;

y: recovery rate;

m: calcium fluoride slag volume in g.

3)²³⁵Activity concentration of U: according to²³⁵U and²³²u count ratio sum²³²U activity, calculating in the measured sample²³⁵U activity concentration, and the calculation formula is shown as formula (3):

wherein:

A_235U: in calcium fluoride slag sample to be measured²³⁵U activity concentration, unit Bq/g;

A_232U: tracer agent²³²U addition, unit: bq;

N_235U: on the plated sheet²³⁵Counting of U;

N_232U: on the plated sheet²³²Counting of U;

e: detecting efficiency;

y: recovery rate;

m: calcium fluoride slag volume in g.

The results are shown in Table 1 below.

TABLE 1 analysis of U isotope content in calcium fluoride slag samples

According to the analysis of the experimental data in the table 1, the method can be used for measuring the content of the U isotope in the calcium fluoride slag sample,²³⁸the content of Pu is 1.32 multiplied by 10^-2-4.50×10^-2Bq/g，²³⁵The content range of Pu is 0.66 multiplied by 10^-3-3.59×10^-3Bq/kg，²³⁴The U content is in the range of 1.89X 10^-2-1.20×10^-1Bq/kg。

In addition, the separation and purification effects of U are required to be noticed by adopting the method. Concrete examinationThe searching method comprises the following steps: taking an actual calcium fluoride slag sample as a detected sample, carrying out nuclide analysis according to the steps (1) to (13), identifying the removal effect of interfering nuclides through an alpha spectrogram measured by various U isotopes, and using a tracer²³²And judging the influence of the removal effect of the macroelements such as Fe on the measurement by the full width at half maximum of the energy peak of the Ualpha.

As can be seen from fig. 2:

(1) in the analysis of uranium isotopes in calcium fluoride slag samples, the types of uranium isotopes in the samples can be identified by an alpha spectrometer, including²³⁸U、²³⁵U、²³⁴U, can also be quantitatively analyzed and simultaneously give²³⁸U、²³⁵U、²³⁴U activity concentration.

(2) The resolution ratio of the U isotope alpha energy peak obtained by the method is good, only the alpha energy peak of the nuclide to be detected is left in the spectrogram, and other nuclides are completely removed, which indicates that the removal effect is very good.

(3) Tracer agent²³²Full width at half maximum (FWHM) of Ualpha energy peak is 26.3KeV, and nuclide to be detected²³⁸U、²³⁵U、²³⁴The full width at half maximum (FWHM) of U is 32.3KeV, 20.7KeV and 31.9KeV respectively, which shows that the resolution of the method is good, and the removal of the macroelements such as Fe is complete.

It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such 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 intended to include such modifications and variations. The foregoing examples or embodiments are merely illustrative of the present invention, which may be embodied in other specific forms or in other specific forms without departing from the spirit or essential characteristics thereof. The described embodiments are, therefore, to be considered in all respects as illustrative and not restrictive. The scope of the invention should be indicated by the appended claims, and any changes that are equivalent to the intent and scope of the claims should be construed to be included therein.