JPH01313800A - Oxidation decomposition processing method for radioactive ion exchange resin - Google Patents

Abstract

PURPOSE:To obtain a high decomposition rate by executing an oxidation decomposition processing by adding oxalate at the time of decomposing a mixed ion exchange resin of weak acidic and weak basic ion exchange resins by using hydrogen peroxide, and iron ion and copper ion as oxidizer, and catalyst, respectively. CONSTITUTION:A water solution containing an iron ion and a copper ion is led into a reaction tank 1 from a catalyst supply port 6, and hydrogen peroxide water is supplied into the reaction tank 1 from a supply port 4. Also, the water solution of oxalate is supplied. In this state, when a single or mixed resin of a weak acidic radioactive ion exchange resin and a weak basic radioactive ion exchange resin is brought to oxidation decomposition by using hydrogen peroxide, and an iron ion and a copper ion as an oxidizer, and a catalyst, respectively, it is executed under the coexistence of an oxalic acid ion. In such a way, from the hydrogen peroxide and the catalyst, an OH radical is generated, oxalate reacts with the generated OH radical and the generation of an organic radical is quickened, the resin is attacked and the structure of the resin is broken down, and a high decomposition rate can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for oxidatively decomposing used ion exchange resin (waste resin) generated from nuclear facilities using hydrogen peroxide as an oxidizing agent and a catalyst.

[Conventional technology]

Among the various solid wastes generated from nuclear power plants, there is ion exchange resin that is discarded after being used in liquid purification processes such as condensate purification system filtration and condensate purification system debasing. These waste resins must be subjected to volume reduction treatment from the viewpoint of space, equipment, environment, etc. This volume reduction treatment method includes combustion method and thermal decomposition method.

Oxidative decomposition methods are known, but each has advantages and disadvantages, and at present it is difficult to determine whether these methods are superior or inferior.

In addition, to reduce the volume of waste resin, hydrogen peroxide (l
There is also a method of decomposing waste resin using a catalyst. This method will be described below. For example, there is a method of decomposing iron at a temperature of about 100°C with hydrogen peroxide using iron as a catalyst. Studies have been conducted on methods for efficiently decomposing ion exchange resins, anion exchange resins, or mixed resins thereof.

Although FIG. 1 is an external view showing the main parts of a laboratory scale continuous decomposition treatment apparatus for explaining this method, a batch type decomposition treatment apparatus may also be used. The apparatus and processing method will be described below with reference to FIG. In Fig. 1, most of the lower part of the reaction tank 1 is inside the water bath 2, and the upper part is rounded by a flange! 3, and connect the hydrogen peroxide supply port 4 to this dome 3. Resin supply port 5. A catalyst supply port 6 is provided, and a cooling pipe 7 is connected thereto. Cooling water enters from a cooling water port 8 as shown by the arrow and is discharged from a cooling water outlet 9. The upper end of the cooling pipe 7 has a gas discharge port 10. A magnetic cooler 11 is provided at the bottom of the water bath 2.

The decomposition treatment of ion exchange resin using this equipment is as follows.For example, the ionic substance ferrous sulfate (
An aqueous solution of FeSO*) and copper sulfate (CuSOa) is introduced into the reaction tank 1 from the catalyst supply port 6 via piping from a storage tank (not shown), and the mixed resin is dispersed and suspended in water. The resin is introduced from the storage tank into the reaction tank l through the resin supply port 5 via piping.

Similarly, a fixed amount of hydrogen peroxide solution is continuously supplied into the reaction tank 1 from the supply port 4, but there is no need to particularly limit the hydrogen peroxide concentration, and a concentration of 30% or 60% of the usual hydrogen peroxide concentration is used. In addition, the capacity of the reaction liquid in the apparatus shown in Fig. 1 is suitably about 10 to 50 d/g of dry resin.The reaction liquid is stirred using a magnetic stirrer 11, and the temperature is controlled by a water bath 2. Decomposition is possible at a constant 0 reaction temperature in the range from room temperature to 100°C, but in order to obtain a high decomposition rate, it is better to keep it at 90°C or higher.The highly concentrated catalyst solution should be diluted with hydrogen peroxide solution. The concentration is kept almost constant. Either the method of keeping the catalyst concentration constant to some extent as described above, or the method of setting the concentration at the beginning and then not changing the concentration can be used. A decomposition reaction occurs, and carbon dioxide gas produced by the decomposition is discharged from the gas outlet 10 of the cooling pipe 7.

After completion of decomposition, remove the waste liquid remaining in reaction tank 1.
Since this waste liquid is strongly acidic, it is neutralized with an alkali such as caustic soda (Mail), and then dried and solidified.

This method of decomposing a mixed resin using iron and copper as catalysts and hydrogen peroxide as an oxidizing agent can achieve high decomposition efficiency, but it appears that this value has already reached its limit, and currently decomposition Volume reduction, which is the original purpose of waste resin processing, is attracting more attention than efficiency. However, at present, strongly acidic cation exchange resins containing sulfone groups (<Sa+) are generated as waste resin, so even if a high decomposition rate can be obtained by the above method, the weight decreases because these heavy sulfone groups remain. Increasing the ratio, that is, becoming an obstacle to volume reduction.

Therefore, there is currently a tendency to use weakly acidic cation exchange resins and weakly basic ion exchange resins that do not have sulfonic groups in place of strong acid and strong base mixed resins.

[Problem to be solved by the invention]

However, when decomposing weakly acidic ion exchange resins and weakly basic ion exchange resins, a problem arises in that it is much more difficult to decompose compared to mixed resins of strong acids and strong bases.

Therefore, the object of the present invention is to decompose mixed waste resins produced when weakly acidic cation exchange resins and weakly basic anion exchange resins are used, using iron ions and copper ions as catalysts and hydrogen peroxide as an oxidizing agent. The object of the present invention is to provide a treatment method that provides a high decomposition rate.

[Means to solve the problem]

In the present invention, a weakly acidic radioactive ion exchange resin and a weakly basic radioactive ion exchange resin, alone or in combination, are oxidized and decomposed using hydrogen peroxide as an oxidizing agent and iron ions and copper ions as a catalyst in the coexistence of oxalate ions. This is a decomposition treatment method performed in

[Effect]

The method of the present invention uses hydrogen peroxide as an oxidizing agent and iron ions and copper ions as catalysts to decompose a mixed ion exchange resin of weakly acidic and slightly basic properties. Oxalate is added to perform oxidative decomposition treatment, and OH is removed from hydrogen peroxide and a catalyst.
A high decomposition rate can be obtained by generating radicals, which react with oxalate to promote the generation of organic radicals, which attack the resin and destroy its structure.

〔Example〕

The apparatus for decomposing a weakly acidic and weakly basic ion exchange resin used in the method of the present invention and its treatment procedure are basically the same as those explained in FIG. Since the only difference is that the resin is additionally charged into the reaction tank 1 and the resin is oxidized and decomposed, a description of the apparatus and processing procedure will be omitted.

Here is a weakly acidic cation exchange Fl! Table 1 shows the results obtained by decomposing M fat. Although sodium oxalate was used as the oxalate, other substances such as oxalic acid and calcium oxalate can also be used.As for the resin, a mixed resin of a weakly acidic cation exchange resin and a weakly basic anion exchange resin can also be used. Similar results can be obtained.

For comparison, Table 1 also shows the results of decomposition treatment without adding sodium oxalate.

Table 1 The HzOz/resin ratio in Table 1 is 1g of dry blast resin.
It represents the ratio of the amount (g) of hydrogen peroxide added to As shown in Table 1, when no oxalate is added, the decomposition rate is 5%, whereas in the present invention with the addition of oxalate, a high decomposition rate of 70% is obtained.

〔Effect of the invention〕

The method of decomposing radioactive ion exchange resin waste using hydrogen peroxide as an oxidizing agent and a combination catalyst of iron and copper is effective, but weakly acidic cation exchange #M as the base resin is effective.
When fatty or weakly basic anion exchange resins were used, it was difficult to decompose these waste resins using this method, but in the present invention, oxalate is added during the decomposition reaction and allowed to coexist in the reaction solution. Therefore, oxalate ions contribute to oxidative decomposition even in the case of a weakly acidic cation exchange resin and a weakly basic anion exchange resin alone or in a mixture thereof, and a high decomposition rate can be achieved.

[Brief explanation of the drawing]

FIG. 1 is an external view of the main parts for explaining an apparatus for oxidatively decomposing an ion exchange resin. 1: reaction tank, 2: water bath, 3: dome, 4: hydrogen peroxide supply port, 5: resin supply port, 6: catalyst supply port, 7:
Cooling pipe, 10: Gas outlet, ll: Magnetic stirrer. Figure 1

Claims (1)

[Claims] 1) Water in which radioactive ion exchange resin is dispersed and suspended, hydrogen peroxide water as an oxidizing agent, an aqueous solution of an ionic substance containing iron ions as a catalyst, and an aqueous solution of an ionic substance also containing copper ions are poured into a reaction tank. In oxidizing and decomposing the radioactive ion exchange resin at a predetermined temperature, a weakly acidic cation exchange resin and/or a weakly basic anion exchange resin is used as the radioactive ion exchange resin, and an aqueous solution of oxalic acid or oxalate is used. A method for oxidative decomposition treatment of a radioactive ion exchange resin, which is carried out by charging the resin into the reaction tank.