KR20040074514A - Method for reducing radioactive waste matter in the decontamination of radioactive contaminated soil - Google Patents

Abstract

PURPOSE: A method is provided to reduce radioactive waste materials by treating the waste solution generated after decontamination of radioactive contaminated soil, through the use of ion exchange resin. CONSTITUTION: A method comprises a first step of treating the radioactive contaminated soil by using a decontaminating agent; and a second step of treating the waste solution generated after decontamination by using an ion exchange resin. The ion exchange resin contains the decontaminating agent used in the first step. The decontaminating agent is selected from the group consisting of EDTA, DTPA, NTA, citric acid, oxalic acid, formic acid, and acetic acid.

Description

METHOOD FOR REDUCING RADIOACTIVE WASTE MATTER IN THE DECONTAMINATION OF RADIOACTIVE CONTAMINATED SOIL}

The present invention relates to a method for reducing waste generated after decontamination of radioactive contaminated soil, and more specifically, the present invention is to treat radioactive contaminated soil with decontamination agent, and to treat radioactive waste solution generated after decontamination treatment with ion exchange resin for radioactivity. The present invention relates to a method for reducing waste generated after decontamination of contaminated soil.

Radioactively contaminated soils can directly damage humans and terrestrial animals and plants. Secondly, they can pollute the groundwater flowing through the soil and adversely affect the entire environment such as the marine and atmospheric environments. Treatment is required. The method of treating radioactive contaminated soil is to measure the radioactive contamination level of the soil, and then transfer the radioactive contaminated soil to a radioactive waste disposal site for long-term storage or to treat the radioactive contaminated soil with decontamination agents according to the measured radioactive contamination degree. Remove radionuclides. If the measured levels of radioactive contamination are very low, it is efficient to treat them as decontaminated soil by treating them with decontamination agents without the need for long-term storage of radioactive soils at radioactive waste disposal sites.

However, when radioactive contaminated soils are treated with decontamination agents, radionuclides can be removed from radioactive contaminated soils, but the resulting waste liquid contains a large amount of radionuclides. In addition, the use of a large amount of decontamination solution in solution produced a considerable amount of waste, which required a high cost. In order to solve this problem, a technique for treating waste generated after decontamination of radioactively contaminated soil has been developed.

In Japanese Patent No. 123293 (1998), a technique for chemical decontamination method and its apparatus is known. The patent relates to a method that can reduce the amount of waste by destroying oxalic acid after decontamination is completed by using oxalic acid and a reducing agent to decontaminate the inside of a nuclear power plant system and installing an ultraviolet irradiation unit. The patent can reduce the amount of waste by destroying oxalic acid, but it cannot be used to regenerate oxalic acid.

In patent application No. 3-41937 (1991), a technique for treating decontamination waste liquor is known. The patent process a neutralizing agent after processing, Ce ⁴⁺ ions to the acid treatment separately from the adsorption ion exchange resin, desorption of ion Ce ⁴⁺ to Ce ⁴⁺ ions waste generated after processing of radioactive contaminated soil with an ion exchange resin To re-use Ce ⁴⁺ ions. The method allows the use of regenerated Ce ⁴⁺ ions but requires separate acid treatment and neutralizer treatment.

The US DOE reported on the use of mixtures of EDTA and ammonium carbonate as decontamination agents and how to recover them. The report describes the use of a mixture of EDTA and ammonium carbonate as a decontaminant to reduce the radioactive levels of radioactive contaminants themselves to levels that can be recycled. However, the above method makes it impossible to regenerate and use the decontamination agent by using and disposing of the decontamination agent several times.

Research by Atomic Energy Canada Limited has known techniques for minimizing waste and improving groundwater quality. The study found that large amounts of contaminated Cd, U, Pb, Fe, Ca, Sr-90, Cs-137 and benzene trichloroethylene contained in groundwater through continuous chemical treatment, filtration and dehydration of low temperature evaporation. In addition to minimizing groundwater volume, the present invention relates to purifying the water quality of groundwater.

In Japanese Patent No. 2002071895A2 (2002), a technique related to a device for reducing the volume of radioactive waste is known. The patent reduces the amount of radionuclides moving downwards and reduces radioactive waste by installing cyclones between the plasma processing vessel to reduce the volume of radioactive waste and the discharge device for depressurizing the plasma processing vessel. An apparatus for facilitating management of a processing apparatus.

Japanese Patent No. 3264897A2 (1991) discloses a technique for treating high level radioactive waste. The patent removes Cs, water and nitric acid by heating, and heats the material generated during the heating process in the absence of oxygen to synthesize the Cs-fixed solid material, which is then heated to form a solid material in the calcined form. will be. In this patent, the amount of waste can be reduced by converting Cs to a solid material, but the decontamination agent cannot be regenerated and used again.

In Japanese Patent No. 63224786A (1987), a technique related to a liquid waste concentrator is known. The patent concentrates the liquid waste in the liquid waste concentrator to reduce the volume of the waste and inputs the liquid waste volume and concentration into the signal of the discharge regulator during the concentration of the liquid waste so that the waste remains at a constant concentration regardless of the type of liquid waste. It is. In this patent, the amount of waste can be reduced by concentrating the liquid waste, but the decontamination agent used cannot be separated and used.

Japanese Patent No. 2001239138A2 (2001) discloses a technique related to an apparatus for treating liquid waste. The patent is to reduce the amount of waste by mounting a filtration membrane that can adsorb ions and remove fine particles in the liquid waste treatment apparatus. In this patent, ions having decontamination efficacy are also removed through the filtration membrane, so that the decontamination agent cannot be regenerated and used.

As described above, in the conventional method of treating radioactive contaminated soil with decontamination agent and treating waste generated therefrom, the amount of waste generated can be reduced. However, the decontamination agent used in the treatment of waste cannot be recycled and reused, which requires excessive disposal costs. Therefore, the amount of waste generated after decontamination of radioactively contaminated soil can be reduced, and at the same time, a method for regenerating and using the decontamination agent used is required.

The present invention is designed to meet the above demands, and an object of the present invention is to treat wastes generated after treating radioactively contaminated soils with decontamination agents to reduce wastes and to treat large amounts of waste liquids. It is to be able to re-use used decontamination agent.

1 shows the concentration of Cs ⁺ ions flowing out according to the waste liquid volume passing through the cation exchange resin when the waste liquid optionally prepared in Experimental Example 1 was treated with a cation exchange resin containing ammonium ions,

2 shows the concentration of Fe ³⁺ ions flowing out according to the waste liquid volume passing through the anion exchange resin when the waste liquid optionally prepared in Experiment 2 is treated with an anion exchange resin containing oxalate ions,

3 is a comparative comparison of the amount of waste generated according to the form of the decontamination agent according to the present invention in Experimental Example 3 and the amount of waste generated by the conventional method.

In order to achieve the above object, the present invention provides a method for reducing waste generated after decontamination of radioactively contaminated soil consisting of treating the radioactively contaminated soil with a decontamination agent and then treating the generated waste liquid with an ion exchange resin.

Hereinafter, the present invention will be described in detail.

The present invention

(1) treating radioactive contaminated soil with decontamination agent (step 1); and

(2) Provides a method for reducing the waste generated after decontamination of radioactive contaminated soil comprising the step (step 2) of treating the waste liquid generated after the treatment with the decontamination agent with an ion exchange resin.

(1) Step 1

Step 1 is a step of treating radioactive soil with decontamination. Specifically, after radioactively contaminated soil is dried, the radioactive contaminated soil is separated by particle size. The decontamination solution containing the decontamination agent is added to the separated soil to bring the decontamination solution into contact with the fine soil having a high radioactive level, so that radionuclides of the radioactive contaminated soil are eluted into the decontamination solution. A decontamination solution containing radionuclides becomes a waste solution.

Radioactively contaminated soils are soils contaminated with radionuclides such as Cs-134, Cs-137, Sr-90 and Co-60. The radionuclides are known to be Co-60 and Cs-137 in Korea. The radioactive contaminated soil is treated with a decontamination agent, which may be an organic acid decontamination agent or an ion exchange decontamination agent depending on a method of removing radionuclides.

Organic acid decontamination agent is selected from the group consisting of ethylenediaminetetraacetic acid (EDTA), DTPA, NTA, citric acid, oxalic acid, formic acid and acetic acid, the organic acid decontamination agent It can be used at 0.0001 to 1.0M for radioactively contaminated soil. When the radioactive contaminated soil is treated with the organic acid decontamination agent, the anion contained in the organic acid decontamination agent forms a complex with the radionuclide so that the radionuclide can be removed from the radioactive contaminated soil.

In addition, the ion exchange decontamination agent is a salt containing a cation selected from the group consisting of ammonium ions and metal ions such as barium ions, cerium ions, vanadium ions, copper ions, sodium ions and iron ions, Decontamination agents can be used in 0.0001 to 1.0M for radioactive soils. When the radioactive contaminated soil is treated with the ion exchange decontamination agent, ion exchange between the ammonium ions and the metal ions and the radionuclide occurs to remove the radionuclide from the radioactive contaminated soil. The performance of the decontamination agent may vary depending on the concentration of the decontamination agent, the acidity, and the contact time for the radioactive soil.

Wastewater generated after decontamination contains metal ions such as iron, calcium, aluminum, magnesium, and silicon. Therefore, after decontaminating radioactive soils, the metals contained in the wastewater must be removed and reused. . Otherwise, a significant volume of waste will be generated.

(2) Step 2

Step 2 is a step of treating the waste liquid generated after the decontamination agent in step 1 with an ion exchange resin.

The ion exchange resin contains ions constituting the decontamination agent of step 1.

The ion exchange resin is a cation or anion adsorbed on the inner surface of the resin, the cation exchange resin or anion exchange resin is used in the present invention.

The cation exchange resin may be a cation exchange resin including H ⁺ ions, but preferably a cation exchange resin including ions constituting the decontamination agent of step 1 in place of the H ⁺ ions.

The cation exchange resin including ions constituting the decontamination agent of step 1 in place of the H ⁺ ions may be purchased by using a cation exchange resin containing Na ⁺ ions, or a cation containing H ⁺ ions or Na ⁺ ions. It is prepared by treating an exchange resin with a decontamination agent, and specifically contains a cation selected from the group consisting of metal ions such as ammonium ions and barium ions, cerium ions, vanadium ions, copper ions, sodium ions and iron ions. It is produced by treating the decontamination agent. The decontamination agent is used at 0.1 to 2.0 M per 100 g of cation exchange resin containing H ⁺ ions or Na ⁺ ions. Preferably, the 0.2 M decontamination solution is placed in a cation exchange resin containing H ⁺ ions or Na ⁺ ions and left for 30 minutes to replace the H ⁺ ions or Na ⁺ ions with cations in the decontamination solution.

If the generated waste liquor is treated with a cation exchange resin containing H ⁺ ions, the waste can be reduced, but the decontaminant regenerated is very small. However, when the waste liquid generated is treated with a cation exchange resin containing ions constituting the decontamination agent of step 1, waste can be reduced, and the decontamination agent used can be regenerated and used again.

Specifically, in the cation exchange resin containing the ions constituting the decontamination agent of the step 1 instead of the H ⁺ ions, the cation shown above is adsorbed on the resin surface. When the waste liquid generated after treating the radioactive contaminated soil with the decontamination agent is treated with the cation exchange resin, the radionuclides contained in the waste liquid are exchanged with the cations adsorbed on the surface of the resin to be removed from the waste liquid. The cation of the decontamination agent is released. Therefore, the waste generated during the decontamination of radioactive soil is changed to the cation exchange resin to which the radionuclide is adsorbed, thereby reducing the weight and volume of the waste and reusing the cation of the decontamination agent flowing out of the cation exchange resin into the decontamination agent. have.

The anion exchange resin may be an anion exchange resin containing OH ⁻ or Cl ⁻ ions, but preferably an anion exchange including ions constituting the decontamination agent of step 1 in place of the OH ⁻ or Cl ⁻ ions. Resin is used.

The OH ^- ions or Cl ^- ions instead of an anion exchange resin containing ions that make up the decontamination agent in the step 1 is OH ^- ions or Cl ^- prepared by treating the anion exchange resin zero decontamination of step 1 including the ion Specifically, it is prepared by treating a decontamination agent selected from the group consisting of EDTA, DTPA, NTA, citric acid, oxalic acid, formic acid and acetic acid. The decontamination agent is used at 0.1 to 2.0 M per 100 g of anion exchange resin containing OH ^- or Cl ^- ions. Preferably, the 0.2 M decontamination solution is placed in an anion exchange resin containing OH ⁻ or Cl ⁻ ions and left for 30 minutes to replace the OH ⁻ or Cl ⁻ ions with anions in the decontamination solution.

If the waste generated is treated with an anion exchange resin containing OH ^- ions or Cl ^- ions, the waste can be reduced, but the decontaminant regenerated is quite minimal. However, when the waste liquid generated is treated with an anion exchange resin containing ions constituting the decontamination agent of step 1, waste can be reduced, and the decontamination agent used can be regenerated and used again.

Specifically, the anion exchange resin including the ions constituting the decontamination agent of step 1 can not only remove radionuclides contained in the waste liquid generated after treating the radioactive contaminated soil with the decontaminant, but also decontaminate the radioactive contaminated soil. Zero treatment can also remove metal ions such as iron, calcium, aluminum, magnesium, and silicon from the soil. That is, when the waste liquid generated after treating the radioactive contaminated soil with the decontamination agent is treated with the anion exchange resin, radionuclides and metal ions contained in the waste liquid as an anion complex are exchanged with anions adsorbed on the resin surface. Can be removed. Therefore, the waste is changed to an anion exchange resin to which radionuclides and metal ions are adsorbed, thereby reducing the weight and volume of the waste.

On the other hand, by treating the waste liquid generated during decontamination with an anion exchange resin, the anion with decontamination efficacy remaining in the waste liquid can be recovered from the effluent and used again as a decontamination agent.

Hereinafter, the present invention will be described in detail by Examples and Experimental Examples.

However, the following examples are merely to illustrate the invention, but the content of the present invention is not limited by the following examples.

<Example 1>

50 g of radioactive contaminated soil was mixed with 500 ml of 0.5 M ammonium nitrate solution for 24 hours and 400 ml of waste solution was obtained by removing radioactive contaminated soil particles and suspended solids.

An H ⁺ cation-exchange resin containing ion (Samyang Corporation, Rohm and Haas Co.) was treated with a 0.2M ammonium nitrate solution 200㎖ 30g contained in the cation exchange resin, H ⁺ ions were transformed into ammonium ions. The column was filled with a cation exchange resin substituted with ammonium ions and passed through the waste solution to obtain an effluent. Regeneration of ammonium nitrate was confirmed by confirming that ammonium ions were detected from the effluent using conventional methods. When a volume of effluent passed through the ion exchange resin capacity, iron, magnesium, and radionuclide cesium and cobalt ions were detected.

Experimental Example 1

When the waste liquid was treated with a cation exchange resin according to the present invention, the concentration of radionuclides in the effluent was measured according to the volume of the waste liquid passing through the cation exchange resin.

Specifically, the ion type of the cation exchange resin was transformed into ammonium ions to prepare a cation exchange resin to which ammonium ions were adsorbed, and the waste liquid thus produced was passed through the cation exchange resin to which the ammonium ions were adsorbed. And by measuring the concentration of radionuclides flowing out therefrom, the concentration of radionuclides contained in the effluent was measured according to the volume of the waste liquid passing through the cation exchange resin.

The experimental method is as follows.

H commonly used⁺Ion 3 g of cation exchange resin (Samyang, Rohm and Haas) was treated with 50 ml of a 0.2 M ammonium nitrate solution.⁺The ions were transformed into ammonium ions. And 0.1M NH₄ ⁺Ion, 0.001M Cs⁺Ion, 0.001M Fe³⁺A waste liquid containing ions was optionally prepared, and the waste liquid prepared above was passed through a cation exchange resin. Cs contained in the effluent from the cation exchange resin depending on the volume of the waste liquid passing through the cation exchange resin⁺The concentration of ions was measured.

The results are shown in Figure 1;

As shown in FIG. 1 , it can be seen that Cs ⁺ ions were detected in the effluent when the volume of the waste liquid passed through was 25 times the bed volume. Therefore, according to the present invention, a considerable amount of Cs ⁺ ions are adsorbed to the cation exchange resin by treating the waste liquid with a cation exchange resin. Conversely, ammonium ions used as ion exchange decontamination agents flow out through a cation exchange resin. Accordingly, the present invention can be seen that with the effect that the waste is reduced thereby changing the waste solution containing the Cs ⁺ ion as a cation exchange resin is adsorbed Cs ^+.

In addition, since the concentration of Cs ⁺ ions contained in the waste liquid arbitrarily prepared in Experimental Example 1 is 20 times or more than the concentration of Cs ⁺ ions contained in the actual waste, a considerable amount of waste is treated when the actual waste is treated with a cation exchange resin. I can cleanse it.

In addition, the solution that flowed out of the cation exchange resin before the Cs ⁺ ions flow out of the cation exchange resin contains ammonium ions having decontamination efficacy and can be regenerated and used again as a decontamination agent.

Experimental Example 2

When the waste liquid was treated with an anion exchange resin according to the present invention, the concentration of metal ions contained in the effluent was measured according to the volume of the waste liquid. The metal ions are ions desorbed from the soil during the decontamination of the radioactive contaminated soil and exist in a state in which they are combined with ions having decontamination efficacy.

Specifically, the ion type of the anion exchange resin was transformed into oxalate ions, and the optionally produced waste liquid was passed through an anion exchange resin to which the oxalate ions were adsorbed. Then, by measuring the concentration of radionuclides flowing out therefrom, the concentration of metal ions contained in the effluent flowing out of the anion exchange resin was measured according to the volume of the waste liquid passing through the anion exchange resin.

The experimental method is as follows.

OH commonly used^-Ion 3 g of an anion exchange resin (Samyang, Rohm and Haas) was treated with 100 ml of a 0.2 M aqueous solution of oxalic acid to obtain OH in the anion exchange resin.^-The ions were transformed into oxalate ions. And 0.1M oxalic acid, 0.002M Fe³⁺A waste liquid containing ions was optionally prepared, in which³⁺Ions form complexes in the form of anions with oxalate ions. The waste solution prepared above was passed through the prepared anion exchange resin. Fe contained in the effluent flowing out of the anion exchange resin according to the volume of the waste liquid passing through the anion exchange resin³⁺The concentration of ions was measured.

The result is shown in Fig.

As shown in FIG. 2 , it can be seen that Fe ³⁺ ions were detected in the effluent when the volume of the waste liquid passed through the anion exchange resin became 80 times the filling volume. Therefore, when the waste liquid is treated with an anion exchange resin, the complex compound containing Fe ³⁺ ions is adsorbed and removed by the anion exchange resin, and the oxalate ions contained in the waste liquid flow out through the anion exchange resin.

In addition, the effluent flowing out of the anion exchange resin before the Fe ³⁺ ions flow out of the anion exchange resin contains oxalate ions having decontamination efficacy and can be used as a decontamination agent so that the decontamination efficacy can be continuously maintained.

Experimental Example 3

According to the present invention, the amount of waste generated when the waste liquid generated by decontamination of radioactive contaminated soil was treated with an ion exchange resin was compared with the amount of waste generated when the waste liquid was treated by the conventional method. Decontamination agents used were citric acid, oxalic acid, salts containing ammonium ions, salts containing sodium ions and salts containing barium ions.

The experimental method is as follows.

(1) 3 g of anion exchange resin containing OH- was treated with 50 ml of 0.2 M citric acid solution to transform OH ^- ions contained in the anion exchange resin into citrate ions. Radioactively contaminated soil was treated with citric acid solution, which is a decontamination agent, and the resulting waste solution was treated with an anion exchange resin containing the citrate ions. The amount of waste generated therefrom was obtained.

(2) 3 g of anion exchange resin containing OH ^- ions was treated with 50 ml of a 0.2 M oxalic acid solution to transform OH ^- ions contained in the anion exchange resin into oxalate ions. Radioactive soil decontamination was treated with oxalic acid as the decontamination agent, and the resulting waste solution was treated with an anion exchange resin containing the oxalate ions. The amount of waste generated therefrom was obtained.

(3) 3 g of a cation exchange resin containing H ⁺ ions was treated with 50 ml of a 0.2 M ammonium nitrate solution to transform the H ⁺ ions contained in the cation exchange resin into ammonium ions. Radioactively contaminated soil was treated with an ammonium nitrate solution, which is a decontamination agent, and the waste solution generated during the decontamination treatment was treated with a cation exchange resin containing ammonium ions. The amount of waste generated therefrom was obtained.

(4) 3 g of a cation exchange resin containing H ⁺ ions was treated with 50 ml of a 0.2 M sodium nitrate solution to transform H ⁺ ions contained in the cation exchange resin into sodium ions. Radioactively contaminated soil was treated with sodium nitrate solution, a decontamination agent, and the resulting waste solution was treated with a cation exchange resin containing the sodium ions. The amount of waste generated from this was calculated.

(5) 3 g of a cation exchange resin containing H ⁺ ions was treated with 50 ml of a 0.2 M barium nitrate solution to deform the barium ions with H ⁺ ions contained in the cation exchange resin. Radioactively contaminated soil was treated with a barium nitrate solution, which is a decontamination agent, and the resulting waste solution was treated with a cation exchange resin containing the barium ions. The amount of waste generated therefrom was obtained.

(6) After treating radioactively contaminated soil with the decontamination agent according to the conventional method, the generated waste solution was treated with a cation exchange resin or an anion exchange resin which was not substituted with decontamination ions. The amount of waste generated therefrom was obtained.

The amount of waste generated in (6) was 100, and the amount of waste generated in (1) to (5) was converted to compare the amount of waste generated in (1) to (6).

The result is shown in Fig.

As shown in FIG. 3 , when the citric acid, oxalic acid, ammonium nitrate solution and sodium nitrate solution were treated with the decontamination agent according to the present invention, the amount of waste generated was 38, 43, 22, and 12, respectively. Showed. When the barium nitrate solution was treated with the decontamination agent, the amount of waste generated was 95, which was insignificant.

The method for reducing the waste generated after the decontamination of the radioactively contaminated soil of the present invention by the above configuration has the following effects.

First, in the method of the present invention, by treating the waste liquid generated during the decontamination of radioactive contaminated soil with an ion exchange resin, the waste liquid can be separated into an effluent liquid containing an ion exchange resin and a decontamination agent containing radionuclides to reduce waste. .

Second, in the method of the present invention, when the ion exchange resin contains constituent ions of the decontamination agent treated with the radioactive soil, the decontamination agent may be regenerated from the effluent and used again.

Third, the method of the present invention can purify a considerable amount of waste liquid.

Claims (11)

(1) treating radioactive contaminated soil with decontamination agent (step 1); and (2) a method for reducing waste generated after decontamination of radioactively contaminated soil comprising the step (step 2) of treating the waste liquid generated after the decontamination treatment with an ion exchange resin. The method for reducing waste generated after decontamination of radioactively contaminated soil according to claim 1, wherein the ion exchange resin contains ions constituting the decontamination agent of step 1. The decontamination agent according to claim 1 or 2, wherein the decontamination agent is selected from the group consisting of EDTA, DTPA, NTA, citric acid, oxalic acid, formic acid and acetic acid, and is used at 0.0001 to 1.0M. How to reduce waste generated. The decontamination agent according to claim 1 or 2, wherein the decontamination agent comprises a cation selected from the group consisting of ammonium ions and metal ions such as barium ions, cerium ions, vanadium ions, copper ions, sodium ions and iron ions, A method for reducing waste generated after decontamination of radioactively contaminated soil, characterized by being used at -1.0 M. The method for reducing waste generated after decontamination of radioactive contaminated soil according to claim 1 or 2, wherein the ion exchange resin is a cation exchange resin or an anion exchange resin. A method according to claim 5, wherein the cation exchange resin is prepared by treating a cation exchange resin containing H ⁺ ions or Na ⁺ ions with a decontamination agent. 7. The radioactivity according to claim 6, wherein the decontamination agent contains a cation selected from the group consisting of ammonium ions and metal ions such as barium ions, cerium ions, vanadium ions, copper ions, sodium ions and iron ions. A method for reducing waste generated after decontamination of contaminated soil. 7. A method according to claim 6, wherein said decontamination agent is used at 0.1 to 2.0 M per 100 g of cation exchange resin containing H ⁺ ions or Na ⁺ ions. A method according to claim 5, wherein the anion exchange resin is prepared by treating a decontamination agent to an anion exchange resin containing OH ^- or Cl ^- ions. 10. The method of claim 9, wherein said decontamination agent is selected from the group consisting of EDTA, DTPA, NTA, citric acid, oxalic acid, formic acid and acetic acid. 10. The method according to claim 9, wherein the decontamination agent is used at 0.1 to 2.0 M per 100 g of anion exchange resin containing OH ^- or Cl ^- ions.