KR102464921B1 - Method for separating radiochemical nuclides from radioactive waste samples - Google Patents

Abstract

A method for rapid sequential and radiochemical separation of ^{238,239,240,241} Pu, ²⁴¹ Am ( ^242,244 Cm), ⁹⁹ Tc, ^89,90 Sr, ^93m,94 Nb, ⁵⁵ Fe and ^59,63 Ni isotopes contained in radioactive waste will be.
According to the present invention, since it is possible to separate alpha and beta emitting nuclides individually through a single sample pretreatment process and iron coprecipitation, the time required for separation can be greatly reduced.

Description

Method for radiochemical separation of radioactive waste samples {METHOD FOR SEPARATING RADIOCHEMICAL NUCLIDES FROM RADIOACTIVE WASTE SAMPLES}

The present invention provides regulated nuclides ^{238,239,240,241} Pu, ²⁴¹ Am ( ^242,244 Cm), ⁹⁹ Tc, ^89,90 Sr, ^93m,94 Nb, ⁵⁵ It relates to a method for sequentially separating Fe and ^59,63 Ni isotopes, and more particularly, ^{238,239,240,241} Pu, ²⁴¹ Am ( ^242,244 Cm), ⁹⁹ Tc, ^89,90 Sr, ^93m,94 Nb contained in radioactive waste, A method for the rapid sequential and radiochemical separation of ⁵⁵ Fe and ^59,63 Ni isotopes.

In order to efficiently manage radioactive waste, the stock of regulated nuclides such as ^{238,239,240,241} Pu, ²⁴¹ Am ( ^242,244 Cm), ⁹⁹ Tc, ^89,90 Sr, ^93m,94 Nb, ⁵⁵ Fe and ^59,63 Ni contained in radioactive waste should be reduced. It must be evaluated quickly and accurately. In order to accurately quantify the nuclides, desired nuclides should be selectively and completely separated from the component elements constituting the samples of various media as well as nuclides coexisting with the nuclides and then measured.

In the existing radionuclide analysis method for radioactive waste, methods for separating only specific nuclides from specific samples or dividing them into alpha-emitting nuclides (Pu, Am) or beta-emitting nuclides (Tc, Sr, Nb, Fe, Ni) are used. However, since radioactive waste samples are not physically and chemically homogeneous, reliable analysis results can be obtained only by sequentially separating the nuclides to be separated from one sample and measuring them individually. When separating a specific nuclide from a specific sample, evaporation of the solution, dissolution, and conversion to a suitable medium are necessary to make a medium solution suitable for each nuclide separation. In addition, when the amount of the analyte sample is small, it is difficult to obtain reliable analysis results for individual nuclide analysis due to the decrease in the amount of the analyte sample. Therefore, there is a need to develop a new separation method capable of overcoming the problems of the existing radioactivity analysis methods and quantifying the desired nuclides quickly and accurately.

Korean Patent Publication No. 10-1785501 (2017.09.29) Korean Patent Publication No. 10-1370573 (2014.02.27)

The present invention provides alpha and beta emitting nuclides [ ^{238,239,240,241} Pu, ²⁴¹ Am ( ^242,244 Cm), ⁹⁹ Tc, ^89,90 Sr, ^93m,94 Nb, ⁵⁵ Fe and ^{59, 63} Ni], and then to provide a method for sequentially separating nuclides using an ion exchange resin.

However, the technical problem to be achieved by the present invention is not limited to the above-mentioned problems, and other problems not mentioned will be clearly understood by those skilled in the art from the following description.

In the method for separating radiochemical nuclide from a radioactive waste sample according to an embodiment of the present invention, a first sample solution for separating Pu, Am, Tc and Sr by pretreating a radioactive waste sample containing alpha and beta nuclides with a strong acid and preparing a second sample solution for separating Nb, Fe and Ni; separating the precipitate and the supernatant by iron co-precipitating the first and second sample solutions at a pH of 8 to 11, respectively; and sequentially separating alpha nuclides of Pu and Am and beta nuclides of Tc, Sr, Nb, Fe and Ni from each of the precipitates and the supernatant.

In addition, according to an embodiment of the present invention, the strong acid includes concentrated nitric acid and concentrated hydrochloric acid, and the first and second supernatant liquids centrifuged after adding HCl solution to the sample obtained by adding the strong acid to evaporation to dryness It can be prepared by dividing the sample solution.

In addition, according to an embodiment of the present invention, the first sample solution is separated into a precipitate containing the alpha nuclides (Pu, Am) and a supernatant containing Tc and Sr by the iron coprecipitation, and the first sample After separation of Pu from the precipitate of the solution, Am may be sequentially separated, and after Tc separation from the supernatant of the first sample solution, Sr may be sequentially separated.

In addition, according to an embodiment of the present invention, the second sample solution is separated into a precipitate containing Nb and Fe and a supernatant containing Ni by the iron co-precipitation, and after separation of Nb from the precipitate of the second sample solution Fe may be sequentially separated, and Ni may be separated from the supernatant of the second sample solution.

In addition, according to an embodiment of the present invention, the HCl solution in which the precipitate of the first sample solution is dissolved is passed through an anion exchange resin column, and then the HCl and NH ₄ I mixed solution is passed through the anion exchange resin column to Pu is purified, and Am passed through the anion exchange resin column is dissolved with HNO ₃ and Al(NO ₃ ) ₃ solution and passed through the TRU-resin column, and then the HCl solution is passed through the TRU-resin column to obtain Am pure separation.

In addition, according to an embodiment of the present invention, the separated Pu or Am may be co-precipitated with an Nd carrier to prepare a sample for alpha-spectrometry measurement.

In addition, according to an embodiment of the present invention, the pH of the supernatant of the first sample solution is set to 2 or less and passed through a TEVA-resin column, and then the HNO ₃ solution is passed through the TEVA-resin column to separate Tc from pure water. In addition, the Sr that has passed through the TEVA-resin column is dissolved in HNO ₃ solution and passed through the Sr-resin column, and then the HNO ₃ solution is passed through the Sr-resin column to separate Sr from pure water.

In addition, according to an embodiment of the present invention, a sample for liquid scintillation counter measurement may be prepared by adding Ultima Gold AB cocktail to the separated Tc or Sr solution.

In addition, according to an embodiment of the present invention, the HCl solution in which the precipitate of the second sample solution is dissolved is passed through the anion exchange resin column, and then the HCl and HF mixed solution is passed through the anion exchange resin column to convert Nb into pure water. Separation, and passing the HCl solution through the anion exchange resin column, Fe can be separated into pure water.

Further, according to an embodiment of the present invention, pure Ni may be separated from the supernatant of the second sample solution by DMG precipitation using a dimethylglyoxime (DMG) solution.

In addition, according to an embodiment of the present invention, a sample for liquid scintillation counter measurement may be prepared by adding Ultima Gold AB cocktail to the separated Nb, Fe or Ni solution.

In the present invention, alpha and beta emitting nuclides [ ^{238,239,240,241} Pu, ²⁴¹ Am ( ^242,244 Cm), ⁹⁹ Tc, ^89,90 Sr, ^93m,94 Nb, ⁵⁵ Fe and ^59,63 Ni] were individually prepared in a single sample pretreatment process. Since it can be separated, the time required for separation can be greatly reduced, and the time for the analyst to be exposed to radiation can be reduced.

In addition, it is possible to separate desired nuclides with high efficiency using an ion exchange resin suitable for the characteristics of nuclide in each separation process. It can be usefully used to quantitatively evaluate the radioactivity concentration of each species.

1 is a schematic diagram showing the time required for separation of regulated nuclides according to the present invention compared with the conventional method.
2 is a schematic diagram showing the sequential separation of isotopes of egg separation regulation nuclide according to the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The following examples are presented to sufficiently convey the spirit of the present invention to those of ordinary skill in the art to which the present invention pertains. The present invention is not limited to the embodiments presented herein, and may be embodied in other forms. The drawings may omit the illustration of parts irrelevant to the description in order to clarify the present invention, and may slightly exaggerate the size of the components to help understanding.

Also, when a part "includes" a certain component, it means that other components may be further included, rather than excluding other components, unless otherwise stated.

In the following embodiments, terms such as first, second, etc. are used for the purpose of distinguishing one component from another, not in a limiting sense. The singular expression includes the plural expression unless the context clearly dictates otherwise.

The present invention relates to essential identified nuclides contained in radioactive waste: Pu ( ^239,240 Pu, ²³⁸ Pu, ²⁴¹ Pu), ²⁴¹ Am ( ²⁴² Cm, ²⁴⁴ Cm), ⁹⁹ Tc, Sr ( ⁹⁰ Sr, ⁸⁹ Sr), Nb ( ^93m Nb , ⁹⁴ Nb), ⁵⁵ Fe and Ni ( ⁵⁹ Ni, ⁶³ Ni) relates to a method for sequentially separating isotopes, and relates to iron coprecipitation and ion exchange resin (anion exchange resin, TRU-resin, TEVA-resin, Sr-resin) ) to a radioisotope separation assay that can quickly and simply isolate the above nuclides.

In the existing nuclide analysis for radioactive waste, a solvent extraction method using an organic solvent such as TBP or TOPO and a method using cation and anion exchange resins were used. There are problems that arise. The present invention relates to Pu ( ^239,240 Pu, ²³⁸ Pu, ²⁴¹ Pu), ²⁴¹ Am ( ²⁴² Cm, ²⁴⁴ Cm), ⁹⁹ Tc, Sr ( ⁹⁰ Sr, ⁸⁹ Sr), Nb ( ^93m Nb, ⁹⁴ Nb), ⁵⁵ Fe and Ni ( ⁵⁹ Ni, ⁶³ Ni) is first separated from the sample medium by sample pretreatment and iron coprecipitation before pure water separation The problem of the existing nuclide analysis method was solved by drastically reducing the steps and separating the desired nuclide with high efficiency.

In the case of conventional alpha and beta emitting nuclides [ ^{238,239,240,241} Pu, ²⁴¹ Am ( ^242,244 Cm), ⁹⁹ Tc, ^89,90 Sr, ^93m,94 Nb, ⁵⁵ Fe and ^59,63 Ni], nitric acid and / or in order to solve various problems caused by the use of strong acids such as hydrochloric acid, the inventors of the present invention reduce the pretreatment step without the need for individual pretreatment operations with a single sample pretreatment operation to significantly shorten the analysis time as well as reduce the amount of strong acid The analysis cost was also reduced.

In the method for separating nuclide according to the present invention, the sample pretreatment step can be performed by a single strong acid pretreatment operation without the need for an individual pretreatment operation. After sample pretreatment, a certain amount of the solution is taken, and ^Pu and Am isotopes are co-precipitated into iron at pH 9 to 11 using ammonia water. ⁹⁰ Sr is isolated sequentially. After dissolving the precipitate co-precipitated with Pu and Am isotopes in 8.0 to 10.0M HCl, ²³⁸ Pu, ^239,240 Pu are separated using an anion exchange resin column, and ²⁴¹ Am is sequentially separated using a TRU-resin column.

Nb and Fe isotopes are co-precipitated into iron at pH 9 to 11 using ammonia water for the remaining pretreatment solution used for the analysis of nuclide, and Ni isotopes are separated from the supernatant by a DMG (dimethylglyoxime) precipitation operation. The precipitate co-precipitated with Nb and Fe isotopes was prepared with 8.0 to 10.0 M HCl. After dissolving in the solution, ^{93m, 94} Nb and ⁵⁵ Fe are sequentially separated using an anion exchange resin column.

Hereinafter, a method for separating radiochemical nuclides from a radioactive waste sample according to the present invention will be described in detail.

In the method for separating radiochemical nuclide from a radioactive waste sample according to an embodiment of the present invention, a first sample solution for separating Pu, Am, Tc and Sr by pretreating a radioactive waste sample containing alpha and beta nuclides with a strong acid and preparing a second sample solution for separating Nb, Fe and Ni; separating the precipitate and the supernatant by co-precipitating the first and second sample solutions, respectively; and sequentially separating the alpha nuclides of Pu and Am and the beta nuclides of Tc, Sr, Nb, Fe and Ni from each of the precipitates and the supernatant.

Sample preparation

In the sample pretreatment according to the present invention, in the case of a solid sample, a strong acid including concentrated nitric acid and/or concentrated hydrochloric acid is added to a predetermined amount of the sample, and then evaporated to dryness slowly on a hotplate. By repeating this operation, the solid sample can be completely decomposed. After adding a certain amount of 0.1 to 2.0M HCl to the evaporated dry sample, centrifugation is performed to discard the precipitate and recover the supernatant. A small amount of the supernatant can be taken and analyzed for Sr, Fe, and Ni stable elements with inductively coupled plasma atomic emission spectroscopy (ICP-AES) to be used for recovery correction. The supernatant may be divided in half to prepare first and second sample solutions separately. The first sample solution is used for isotope analysis of Pu, Am, Tc and Sr, and the second sample solution is used for separation of Nb, Fe and Ni isotopes.

In the case of a liquid sample, the sample solution can be divided in half and used as the first and second sample solutions without special sample pretreatment.

1st sample solution iron coprecipitation

In the first sample solution, the alpha nuclides (Pu, Am) are co-precipitated with iron to separate Tc and Sr, and after Pu separation from the precipitate of the first sample solution, Am is sequentially separated, and in the supernatant of the first sample solution After Tc separation, Sr can be sequentially isolated.

Specifically, for iron co-precipitation, an iron carrier is added to the first sample solution, and then the pH is adjusted to 9 to 11 using ammonia water (NH ₄ OH), so that the Pu and Am isotopes are co-precipitated into iron to form a precipitate. When iron precipitation is formed, it can be left at room temperature after aging the iron precipitation by heating it on a hot plate. After iron coprecipitation, centrifugation is performed to separate the supernatant from Tc and Sr, and the precipitate can be used to separate Pu and Am.

At this time, in order to correct the chemical yield, 1mL of ²⁴² Pu (0.5 Bq/mL), ²⁴³ Am (0.3 Bq/mL), ^99m Tc (50 Bq/mL), and Sr (5mg/mL) was aliquoted before adding ammonia water and sampled. can be added to the solution.

Pu isotope separation

From the iron precipitate in which Pu and Am isotopes are precipitated, Pu isotopes ( ^239,240 Pu, ²³⁸ Pu, ²⁴¹ Pu) can be separated using an anion exchange resin column.

8.0 to 10.0M HCl and 0.01 to 0.3% H ₂ O ₂ solution may be added to dissolve the iron precipitate to prepare a Pu separation sample solution. Highly volatile H ₂ O ₂ can be freshly prepared every time Pu is separated. The disposable polyethylene column is filled with anion exchange resin and the height of the resin bed can be adjusted with distilled water to about 3 cm. After passing 8.0 to 10.0M HCl through the anion exchange resin column, the anion exchange resin column composition is the same as the Pu separation sample solution, and then the sample solution is passed through slowly.

After washing by adding 8.0 to 10.0M HCl and 0.01 to 0.3% H ₂ O ₂ to the centrifuge tube, the washing solution is passed through the column, and then 8.0 to 10.0M HCl can be added to wash the column. The filtrate and washing solution passing through the column can be used for Am separation.

By passing 8.0 to 10.0M HCl and 0.01 to 0.1M NH ₄ I solution through an anion exchange resin column, the Pu isotope ( ^239,240 Pu, ²³⁸ Pu) component is finally separated.

Am isotope separation

Am isotopes [ ²⁴¹ Am ( ²⁴² Cm, ²⁴⁴ Cm)] passed through an anion exchange resin column can be separated using a TRU-resin column.

The Am component that has passed through the anion exchange resin column is evaporated to dryness on a hot plate, and concentrated nitric acid is added to evaporate to dryness to remove the hydrochloric acid component. 1.0 to 3.0M HNO ₃ and 0.1 to 1.0M Al(NO ₃ ) ₃ solution may be added to dissolve the sample. If the sample does not melt well, the dried sample can be completely dissolved by heating it slowly on a hot plate.

When a certain amount of 0.1 to 1.0 M potassium thiocyanate is added to the Am separation sample solution and the color of the sample solution turns red, 0.5 to 1.5 M ascorbic acid is added to reduce Fe(III) to Fe(II). can do it If a precipitate is formed, it can be removed by centrifugation.

A disposable polyethylene column is filled with TRU-Resin, and 1.0 to 3.0 HNO ₃ solution is passed through the column to make the column the same as the composition of the Am separation sample solution, and then the Am separation sample solution is slowly passed through the TRU-resin column. The column is then washed with a 1.0-3.0 HNO ₃ solution. The above operation can be continued three or more times.

The Am isotope [ ²⁴¹ Am ( ²⁴² Cm, ²⁴⁴ Cm)] component is finally separated with a 3.0-5.0M HCl solution.

Preparation and measurement of Pu, Am measurement samples

The separated Pu and Am components may be co-precipitated with an Nd carrier to prepare a sample for alpha-spectrometry measurement. For both Pu and Am components, the measurement sample can be prepared in the same way as below.

After the solution containing the separated Pu or Am component is evaporated to dryness, a small amount of concentrated nitric acid is added to remove organic matter. After addition of Nd carrier (0.5 mg/mL) and 30-50% HF, it can be left for about 30 minutes.

After setting the pump and pressure reducing flask, raise the membrane filter, wash the filter with Nd-substrate solution, and drop the sample solution on the membrane filter one drop at a time. After washing the sample container and membrane filter with distilled water, the membrane filter was dried at room temperature to obtain Pu isotopes [ ^239,240 Pu, ²³⁸ Pu] or Am isotopes [ ²⁴¹ Am ( ²⁴² Cm, ²⁴⁴ Cm)] using an alpha spectrometer. can be quantified.

Meanwhile, after Tc separation from the supernatant of the first sample solution, Sr may be sequentially separated.

After the centrifugation, a small amount of the supernatant stored for the separation of Tc and Sr may be taken, and the element Sr may be quantified by inductively coupled plasma atomic emission spectroscopy (ICP-AES), and used for chemical yield calculation.

Tc separation and measurement

A small amount of concentrated nitric acid is added to the supernatant of the first sample solution to adjust the pH to 2 or less, and after adding a certain amount of 20 to 50% H ₂ O ₂ , it can be heated on a hot plate and left at room temperature.

After filling the disposable polyethylene column with TEVA-Resin and passing 0.01 to 0.2M HNO ₃ through the column to have the same composition as the Tc separation sample solution, the Tc separation sample solution is slowly passed through. The filtrate and washing solution of the Tc separation sample solution that has passed through the TEVA-resin column can be stored for use in Sr separation.

Here, 0.01 to 0.03 HNO ₃ and 0.1 to 1.0M HF solution may be passed through the column to remove the Th component. The column is then washed with 0.05-0.2M HNO ₃ .

7.0 to 9.0M HNO ₃ is passed through the column to separate the Tc component, collected in a liquid scintillation vial, and then ^99m Tc is measured with a gamma spectrometer to determine the recovery rate. After measuring the recovery rate, Ultima Gold AB cocktail can be added to the separated sample to measure ⁹⁹ Tc with a liquid scintillation counter.

Sr separation and measurement

After the filtrate and washing solution passed through the TEVA-resin column are evaporated to dryness on a hot plate, 7.0 to 9.0M HNO ₃ is added to dissolve the dry matter.

After filling the disposable polyethylene column with Sr-Resin and passing 7.0 to 9.0M HNO ₃ through the column to have the same composition as the Sr separation sample solution, the Sr separation sample solution is slowly passed through. Wash the beaker with 7.0-9.0M HNO ₃ and pass the wash solution through an Sr-resin column.

Here, 2.0 to 4.0M HNO ₃ and 0.01 to 0.1M oxalic acid are passed through the Sr-resin column to remove interfering elements (tetravalent nuclide), and 7.0 to 9.0M HNO ₃ is passed through the Sr-resin column. to remove oxalic acid and yttrium elements attached to the column.

Sr can be separated in the Sr-resin column by passing 0.01 to 0.1M HNO ₃ . After the separated Sr solution is evaporated to dryness, the weight is measured to calculate the Sr recovery rate, or a small amount of the separated Sr solution is taken and the Sr element is quantified with an inductively coupled plasma atomic emission spectrometer (ICP-AES) to obtain the chemical yield.

After transferring the Sr solution in which the Sr precipitate is dissolved using 0.1 to 2.0M HNO ₃ to a liquid scintillation vial, Ultima Gold AB cocktail is added to measure ⁹⁰ Sr with a liquid scintillation counter.

Nb, Fe, and Ni isotopes can be separated from the second sample solution prepared separately after pretreatment.

2nd sample solution iron coprecipitation

In the second sample solution, Nb and Fe are co-precipitated with iron to separate from Ni, and after Nb is separated from the precipitate of the second sample solution, Fe is sequentially separated, and Ni can be separated from the supernatant of the second sample solution.

Specifically, when the pH is adjusted to 9 to 11 using aqueous ammonia (NH ₄ OH) and iron precipitation is generated, the iron precipitate is aged by heating on a hot plate, and then left at room temperature for about 3 hours or more. After iron co-precipitation, centrifugation is performed, and the supernatant is used for Ni separation, and the iron precipitate can be used for Nb and Fe separation.

At this time, in order to correct the chemical yield, Nb (5mg/mL), Fe (10mg/mL), and Ni (5mg/mL) may be aliquoted and added to the sample solution before the addition of ammonia water.

Nb Isolation and Measurement

From the precipitate in which Nb and Fe isotopes are precipitated, Nb isotopes ( ^93m Nb, ⁹⁴ Nb) can be separated using an anion exchange resin column.

By adding 8.0 to 10.0M HCl, it can be dissolved by adding to the iron precipitate to prepare a Nb separation sample solution. The disposable polyethylene column is filled with anion exchange resin and the height of the resin bed can be adjusted with distilled water to about 3 cm. After passing 8.0 to 10.0M HCl through the anion exchange resin column, the anion exchange resin column composition is the same as the Nb separation sample solution, and then the sample solution is passed through slowly.

After washing by adding 8.0 to 10.0 M HCl to the centrifuge tube, the washing solution may be passed through an anion exchange resin column, and then 8.0 to 10.0 M HCl may be added to wash the column.

The Nb isotope ( ^93m Nb, ⁹⁴ Nb) component is finally separated by passing 5.0 to 7.0M HCl and 0.01 to 0.2M HF solution through an anion exchange resin column.

After the separated Nb solution is evaporated to dryness and dissolved in 0.1 to 2.0M HCl, a small amount is taken and the Nb element is quantified by inductively coupled plasma atomic emission spectroscopy (ICP-AES) to obtain the chemical yield.

After transferring the pure separated Nb solution to a liquid scintillation vial, ^93m Nb and ⁹⁴ Nb can be quantitatively measured with a liquid scintillation counter by adding Ultima Gold AB cocktail.

Fe separation and measurement

After eluting Fe from the anion exchange resin column with 0.01 to 0.2M HCl and collecting it in a centrifuge tube, a small amount of 0.1 to 1.0M ammonium phosphate is added.

By adjusting the pH to 2 to 4 using aqueous ammonia (NH ₄ OH), iron phosphate precipitates are formed, and the supernatant can be removed by centrifugation. Then, distilled water may be added thereto and centrifuged to remove the supernatant.

After dissolving the precipitate using HCl, the solution is transferred to a liquid scintillation vial, and a small amount is taken and the element of Fe is quantified by inductively coupled plasma atomic emission spectroscopy (ICP-AES) to obtain the chemical yield.

After transferring the pure separated Fe solution to a liquid scintillation vial, a small amount of concentrated phosphoric acid (H ₃ PO ₄ ) is added until the yellow color of the Fe solution disappears, and Ultima Gold AB cocktail is added to quantify ⁵⁵ Fe with a liquid scintillation counter. can be measured

Meanwhile, Ni can be separated from the supernatant of the second sample solution by using DMG precipitation.

After the centrifugation, a small amount of the supernatant stored for Ni separation may be taken and the Ni element may be quantified with an inductively coupled plasma atomic emission spectrometer (ICP-AES), and used for chemical yield calculation.

Ni separation and measurement

The pH is adjusted to 1 to 3 using concentrated hydrochloric acid in the supernatant of the second sample solution. At this time, the blue color of the solution disappears. Then, the solution is cooled by heating on a hot plate, and then the pH is adjusted to 7 to 8 using HCl and aqueous ammonia (NH ₄ OH).

After adding 1 to 10 ml of 0.1 to 2.0M ammonium citrate dibasic solution, the pH is adjusted to 7 to 9 with aqueous ammonia (NH ₄ OH). After adding 1 to 10 ml of 1% DMG (dimethylglyoxime) solution, the mixture is stirred to ripen the pink precipitate (Ni-DMG). In order to remove impurities contained in Ni, 8.0 to 10.0 M HCl is added to Ni-DMG precipitation to dissolve the precipitate, and then 0.1 to 2.0 M ammonium citrate solution may be added. Again, after adjusting the pH to 7 to 9 with ammonia water, 1 to 10 mL of 1% DMG solution is added and stirred to repeat the precipitation (Ni-DMG) operation, so that only the Ni component can be separated from pure water.

Nickel-DMG precipitates are separated using a filtering device equipped with a PP filter (polypropylene filter), and the precipitate can be washed by adding a washing solution to the filtering device.

The PP filter (polypropylene filter) and the precipitate can then be heated in an electric furnace to convert the precipitate chemical form from Nickel-DMG to Nickel Oxide.

After dissolving the nickel oxide precipitate using dilute hydrochloric acid, take a small amount and quantify the Ni element with inductively coupled plasma atomic emission spectroscopy (ICP-AES) to obtain the chemical yield.

⁵⁹ Ni and ⁶³ Ni can be quantified by liquid scintillation counter by adding Ultima Gold AB cocktail to Ni sample.

The sequential nuclide separation method of radioactive waste according to the present invention significantly shortens the time required for nuclide analysis compared to the existing individual nuclide analysis method, and uses a simple ion exchange resin to accurately separate desired nuclides from interfering elements with high yield. It is possible to dramatically reduce the amount of waste generated in the process of separating nuclides.

Hereinafter, it will be described in more detail through preferred embodiments of the present invention.

Example

Radioactive waste samples containing alpha and beta emitting nuclides (Pu, Am / Tc, Sr, Nb, Fe, Ni) were separated according to the above-described method for separating nuclides of the present invention.

<Sample pretreatment>

1 to 10 g of a solid sample was placed in a beaker, 1 mL of concentrated nitric acid (HNO ₃ ) and 3 mL of concentrated hydrochloric acid (HCl) were added, and then slowly evaporated to dryness on a hot plate. After adding 22mL of 0.5M HCl to the evaporated dry sample, centrifugation discards the precipitate and recovers the supernatant, 2mL is for recovery correction, 10mL of the first sample solution for Pu, Am, Tc and Sr isotope analysis, and Nb , was prepared as a second sample solution 10mL for Fe and Ni isotope analysis.

<First sample solution iron coprecipitation>

To calibrate the chemical yield, 1 mL of ²⁴² Pu (0.5 Bq/mL), ²⁴³ Am (0.3 Bq/mL), ^99m Tc (50 Bq/mL) and Sr (5 mg/mL) were added in aliquots to the first sample solution, respectively. did.

For iron co-precipitation, 1 mL of an iron carrier (10 mg/mL) is added to the sample solution, and then the pH is adjusted to 9-10 using 15 M aqueous ammonia (NH ₄ OH) to produce iron precipitate, and heated to 60°C on a hot plate. After aging, it was left at room temperature for at least 3 hours.

<Pu and Am separation>

Dissolve by adding 15mL of 9M HCl / 0.1% H ₂ O ₂ to the centrifuged precipitate, and a disposable polyethylene column filled with 2mL of anion exchange resin (Bio-Rad AG 1x8) (separation tube size: filling height 70mm, inner diameter 4mm) After passing 10mL of 9M HCl, 20mL of 9M HCl / 0.05M NH ₄ I was passed through the column to separate the Pu component.

The Am component sample passed through an anion exchange resin column for Pu separation was evaporated to dryness, and 5 mL of concentrated nitric acid was added to remove the hydrochloric acid component. 2M HNO ₃ / 0.5M Al(NO ₃ ) ₃ 10mL was added to dissolve the sample, and 1 drop of 0.5M potassium thiocyanate and 6 drops of 1M ascorbic acid were added to reduce Fe(III) to Fe(II). After passing the sample solution through a disposable polyethylene column filled with TRU-Resin ^TM 3.5mL (2g) and washing three times, 4M HCl 10mL was added to elute and separate Am.

After adding 1 mL of Nd transporter (0.5 mg/mL) and 1 mL of 40% HF to the separated Pu and Am solutions, leave them for 30 minutes, and quantify the Pu and Am components using a 0.45 μm pore size membrane filter and alpha spectrometer, respectively. measured.

<Separation of Tc and Sr>

On the other hand, to separate Tc, the supernatant of the first sample solution is adjusted to pH 1, 30% H ₂ O ₂ 5mL is added to the sample solution, heated on a hot plate at 60°C for about one hour, and then at room temperature for about 30 minutes was left After passing 0.1M HNO3 5mL through a disposable polyethylene column filled with TEVA _- Resin ^TM _3.5mL (2g) to make the column the same as the sample solution composition, slowly pass the sample solution through the TEVA resin column, 0.02M HNO3 / 5mL of 0.5M HF was passed through to remove Th component. After passing 8M HNO ₃ 10mL, Tc was separated from the column and collected in a liquid scintillation vial. Then, the recovery rate was measured by measuring ^99m Tcm with a gamma spectrometer.

After evaporating the filtrate and washing solution that passed through the TEVA resin column to dryness, 8M HNO ₃ 10mL was added to dissolve the dry matter. After passing the sample solution through a disposable polyethylene column filled with Sr-Resin ^TM _3.5mL (2g), the beaker was washed using 5mL of 8M HNO3, and the washing solution was passed through the column, _and 15mL of 3M HNO3 / 0.05M oxalic acid was added. It was passed through a column to remove tetravalent radionuclides interfering elements. Then, 8M HNO ₃ 10 mL was passed through the column to remove oxalic acid and yttrium elements attached to the column.

Sr was separated from the column by passing 10mL of 0.05M HNO3 _. Sr recovery was calculated by transferring the separated Sr solution to a 1/8 inch stainless steel planchet cleaned with alcohol, and measuring the weight after evaporation to dryness.

<Second sample solution iron coprecipitation>

In order to correct the chemical yield, 1 mL of Nb (5 mg/mL), Fe (10 mg/mL) and Ni (5 mg/mL) were added to the second sample solution in aliquots.

The pH was adjusted to 9-10 with 15M aqueous ammonia (NH ₄ OH), and when iron precipitation was formed, it was aged by heating at 60° C. and left at room temperature for 3 hours or more.

<Separation of Nb and Fe>

15mL of 9M HCl was added to the centrifuged precipitate to dissolve the precipitate, and 10mL of 9M HCl was passed through a disposable polyethylene column filled with 2mL of an anion exchange resin (Bio-Rad AG 1x8), and then the sample solution was passed through. After washing with 10 ml of 9M HCl, the washing solution was passed through the column, and then 9M HCl The column was washed by adding 10 ml.

6M HCl / 0.1M HF 10mL was passed through the column to separate the Nb component. The separated Nb solution was evaporated to dryness, dissolved in 5 mL of 1M HCl, 1 mL was taken, and the chemical yield was obtained by quantifying Nb with ICP-AES, and 15 mL of Ultima Gold AB cocktail was added to the Nb solution to quantify the isotope with a liquid scintillation counter. .

Then, for Fe extraction, 20 mL of 0.1M HCl was added to an anion exchange resin column to elute Fe, and after collecting in a centrifuge tube, 2.0 mL of 0.5M ammonium phosphate was added. The pH was adjusted to 3 using ammonia water, and an iron phosphate precipitate was generated, followed by centrifugation, and the supernatant was discarded. 20 mL of distilled water was added to the centrifuge tube, followed by centrifugation, and the supernatant was discarded again.

Dissolve the precipitate in 3mL of 5M HCl, transfer the solution to a liquid scintillation vial, wash the beaker using 2mL of 0.1M HCl, transfer the solution to the liquid scintillation vial, take 1mL, and quantify Fe element by ICP-AES Thus, the chemical yield was obtained. After adding a few drops of concentrated phosphoric acid (H ₃ PO ₄ ) until the yellow color of the separated Fe solution disappeared, 15 mL of Ultima Gold AB cocktail was added, and ⁵⁵ Fe was quantified with a liquid scintillation counter.

<Ni separation and measurement>

1 mL of the centrifuged supernatant of the second sample solution was taken and Ni element was quantified by ICP-AES and used for chemical yield calculation.

Concentrated hydrochloric acid was used in the supernatant to adjust the pH to 2, and after the blue color disappeared, the sample solution was heated and allowed to cool. The pH was adjusted to 7-8 using hydrochloric acid and aqueous ammonia, 5 mL of 1M ammonium citrate solution was added, and then the pH was adjusted to 8 with aqueous ammonia. Then, 5 mL of 1% DMG solution was added and stirred to mature the precipitate (Ni-DMG). To remove impurities contained in Ni, add 5 mL of 9M HCl to Ni-DMG precipitation to dissolve the precipitate, add 5 mL of 1M ammonium citrate solution, adjust the pH to 8 with ammonia water, add 5 mL of 1% DMG solution, and stir to precipitate (Ni-DMG) operation was repeated to separate pure Ni components only.

Ni-DMG precipitates were separated using a 25 mm filtering device equipped with a polypropylene filter having a 0.1 μm pore size.

After washing the beaker with 95% ethyl alcohol, the washing solution was added to the filtering device to wash the precipitate.

The polyethylene filter and the precipitate were placed in a glass vial (20 mL) and heated in an electric furnace at 550° C. for more than 4 hours to convert the chemical form of the precipitate from Ni-DMG to Ni-oxide. After dissolving the Ni-oxide precipitate using 5 mL of 0.1M HCl, 1 mL was taken, and Ni was quantified by ICP-AES to determine the chemical yield. ⁵⁹ Ni and ⁶³ Ni were quantified using a liquid scintillation counter by adding 16 mL of Ultima Gold AB cocktail to a glass vial containing the separated Ni sample.

As in the above-described embodiment, after separating the radioactive waste containing alpha and beta emitting nuclides (Pu, Am / Tc, Sr, Nb, Fe, Ni) in 4 repetitions by the method of separating nuclides of the present invention, the recovery rate is Measured and the average and standard deviation of the recovery rate are shown in Table 1 below.

Analytical nuclide Recovery (%) Recovery Measuring Instrument alpha emitting nuclide Pu 91.2 ± 5.7 Alpha Spectrometer Am 73.4 ± 2.4 Alpha Spectrometer beta-emitting nuclide Tc 89.5 ± 4.1 Gamma Spectrometer Sr 80.5 ± 4.9 Inductively Coupled Plasma Atomic Emission Spectroscopy Nb 94.7 ± 5.2 Inductively Coupled Plasma Atomic Emission Spectroscopy Fe 92.3 ± 6.1 Inductively Coupled Plasma Atomic Emission Spectroscopy Ni 78.2 ± 8.2 Inductively Coupled Plasma Atomic Emission Spectroscopy

As a result of using the nuclide separation method presented in the present invention for radioactive waste, the average recovery rate for alpha and beta nuclides is mostly 70% or more and the standard deviation is also calculated within 10%. accuracy could be ensured. The sequential nuclide separation method of radioactive waste according to the present invention significantly reduces the time required for nuclide analysis compared to the existing individual nuclide analysis method, and can be usefully used as a tool to quickly and accurately evaluate the content of nuclides to be analyzed. was found to be

In the foregoing, exemplary embodiments of the present invention have been described, but the present invention is not limited thereto, and those of ordinary skill in the art will not depart from the concept and scope of the following claims. It will be appreciated that various modifications and variations are possible.

Claims (11)

Preparing a first sample solution for separating Pu, Am, Tc and Sr and a second sample solution for separating Nb, Fe and Ni by pretreating a radioactive waste sample containing alpha and beta nuclides with a strong acid;
separating the precipitate and the supernatant by iron co-precipitating the first and second sample solutions at a pH of 8 to 11, respectively; and
Including; sequentially separating the alpha nuclides of Pu and Am and the beta nuclides of Tc, Sr, Nb, Fe and Ni from each of the precipitates and the supernatant;
The second sample solution is separated into a precipitate containing Nb and Fe and a supernatant containing Ni by the iron co-precipitation,
After separation of Nb from the precipitate of the second sample solution, Fe is sequentially separated, and Ni is separated from the supernatant of the second sample solution,
A radiochemical separation method of radioactive nuclides from a radioactive waste sample in which Ni is purely separated by DMG precipitation using a dimethylglyoxime (DMG) solution from the supernatant of the second sample solution. According to claim 1,
The strong acid includes concentrated nitric acid and concentrated hydrochloric acid, and the supernatant solution centrifuged after adding HCl solution to the sample evaporated and dried by adding the strong acid is divided into the first and second sample solutions. Radiation of radioactive waste samples Methods for chemical separation of nuclides. According to claim 1,
The first sample solution is separated into a precipitate containing the alpha nuclides (Pu, Am) and a supernatant containing Tc and Sr by the iron coprecipitation,
A method for separating radiochemical nuclides from a radioactive waste sample, characterized in that after Pu separation from the precipitate of the first sample solution, Am is sequentially separated, and Sr is sequentially separated after Tc separation from the supernatant of the first sample solution. delete 4. The method of claim 3,
After passing the HCl solution dissolving the precipitate of the first sample solution through the anion exchange resin column, the HCl and NH ₄ I mixed solution is passed through the anion exchange resin column to separate Pu as pure water,
After dissolving Am passing through the anion exchange resin column with HNO ₃ and Al(NO ₃ ) ₃ solution and passing it through a TRU-resin column, the HCl solution is passed through the TRU-resin column to separate Am from pure radioactive waste A method for separation of radiochemical nuclides from a sample. 6. The method of claim 5,
A method for separating radiochemical nuclides from radioactive waste samples, characterized in that the separated Pu or Am is co-precipitated with an Nd carrier to prepare a sample for alpha-spectrometer measurement. 4. The method of claim 3,
The pH of the supernatant of the first sample solution is set to 2 or less and passed through a TEVA-resin column, and then the HNO ₃ solution is passed through the TEVA-resin column to separate Tc into pure water,
Radiochemical separation method of radioactive waste samples in which Sr that has passed through the TEVA-resin column is dissolved in HNO ₃ solution and passed through the Sr-resin column, and then the HNO ₃ solution is passed through the Sr-resin column to separate Sr into pure water. . 8. The method of claim 7,
A method for separating radiochemical nuclides from a radioactive waste sample, characterized in that the sample for liquid scintillation counter measurement is prepared by adding Ultima Gold AB cocktail to the separated Tc or Sr solution. According to claim 1,
After passing the HCl solution in which the precipitate of the second sample solution is dissolved through an anion exchange resin column, the HCl and HF mixed solution is passed through the anion exchange resin column to separate pure Nb,
A radiochemical nuclide separation method of a radioactive waste sample in which pure Fe is separated by passing an HCl solution through the anion exchange resin column. delete According to claim 1,
A radiochemical separation method of radioactive waste samples, characterized in that by adding Ultima Gold AB cocktail to the separated Nb, Fe or Ni solution to prepare a sample for liquid scintillation counter measurement.

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