JPS58161898A - Chemical decomposition of radioactive ion exchange resin - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method for chemically decomposing a used radioactive ion exchange resin, and more particularly to a method for oxidatively decomposing the resin with hydrogen peroxide in an aqueous ferric sulfate solution. .

[Technical background of the invention]

A variety of solid wastes are generated at nuclear power plants, but as the final disposal method for most of them has not yet been established and the waste is in flux, it is mainly stored in tanks and the like. Therefore, reducing the amount of waste generated is an important and urgent issue in storage management. Among these solid wastes, used radioactive ion exchange resins are the main ones, and reducing their volume will greatly contribute to reducing the amount of waste generated.

As a method for chemically decomposing an ion exchange resin to reduce its volume, there are incineration methods, thermal decomposition methods, chemical decomposition methods, and the like. Incineration is literally a method of burning, and many methods are under development. However, when incinerating in an incinerator, thermal violet control is required, so pretreatment such as drying and a method for supplying resin must be devised, making operations and equipment complicated.

In addition, harmful gases such as 80x and NOx are generated as incineration gas, so post-treatment called waste gas treatment is required, and these gases are highly corrosive, making it difficult to select equipment materials. However, since raw materials are processed in a high-temperature environment, there is a problem unique to the handling of radioactivity: radioactive components volatilize and migrate to the gas side, so-called nuclide migration.

The thermal decomposition method is a method of thermally decomposing the resin by cutting off the supply of oxygen, and because the resin component is thermally decomposed at high temperatures in an inert gas atmosphere, it has the advantage of generating less soot and dust compared to the incineration method. have However, this method requires an extra step of burning the decomposed gas, and, like the incineration method, there are problems with the generation of harmful gases, corrosion of equipment materials, and transferability of radioactive nuclear harvest.

The chemical decomposition method oxidizes and decomposes the resin through a chemical reaction with a chemical, mainly using hot concentrated sulfuric acid (130°C to 300°C).
It is known to oxidize and decompose nitric acid with hydrogen peroxide by carbonizing the resin, but the major problem with this method is that the strong acid and oxidizing agent must be handled at extremely high temperatures. ,!
i! The selection of materials is extremely difficult. At present, glass is used for laboratory scale -t'', and tantalum is used in actual equipment, but not all material issues have been resolved with tantalum as well.

In addition to methods using concentrated sulfuric acid and nitric acid or hydrogen peroxide,
Oxide exchange with hydrogen peroxide in ferric nitrate # solution64)
1! It has been confirmed that L cannot be processed.

In addition, as an organic analysis reagent, there is also the Tzenton reagent method, in which hydrogen peroxide is added to an aqueous ferrous sulfate solution to decompose organic substances, and the solvent component is dissolved in an alkaline solution while heating with hydrogen oxide. Although decomposition methods have been reported, there is no mention of whether these methods can decompose ion exchange resins.

[Purpose of the invention]

The present invention has been made in view of the above points, and by contacting a radioactive ion exchange resin with hydrogen peroxide in an aqueous ferric sulfate solution, it is possible to improve not only a cation exchange resin but also an anion exchange resin using conventional techniques. In contrast, the present invention aims to provide a chemical decomposition method for radioactive ion exchange resins that can be easily oxidized and decomposed at low temperatures.

[Embodiments of the invention]

An embodiment of the present invention will be described below.

Add the ion exchange wIAWI to be decomposed to the ferric sulfate aqueous solution, then add hydrogen peroxide solution and leave it at room temperature while stirring. Decomposes into residues. In this case, it is possible to decompose the ion exchange resin dried in reaction #11 in which the Fes+ concentration is about 0.03 mol/1 or more and the hydrogen peroxide concentration is 8% or more into about 501 parts or more.

Although the above example adopted a batch method, the decomposition process is not limited to this example, and it is also possible to perform the decomposition process in a semi-batch method or a continuous method.

In this case, a method of continuously adding potassium while dropping hydrogen peroxide solution at a constant flow rate over time, a method of dropping a ferric sulfate aqueous solution in the same way, or a method of adding hydrogen peroxide solution and ferric sulfate water bath One possible method is to drop both liquids continuously. In the method of continuously supplying hydrogen peroxide solution, 11
It has been experimentally confirmed that the tree can be disassembled using less electricity than in the case of a split method.

Also, sulfur # in the reaction solution! The concentrations of ferric iron and dihydrogen peroxide are not limited to the one-time conditions of the example, but can take a wider range of fIk degrees.

In addition, although the oxidation reaction proceeds at room temperature, slight heating (
The temperature of the reaction solution is 100°C or lower), which increases the N reaction rate and allows for faster oxidation. and the method q) of the present invention, the better one is i:j(')
, mark the book with an X to indicate the difference.

〔Effect of the invention〕

As is clear from the above explanation, the chemical decomposition method of the present invention has the following advantages compared to conventional methods.

b) Since room temperature is sufficient at the start of the reaction, the decomposition operation is easy and there is less burden on equipment and equipment materials.

-) Since the only decomposition product is 1,000 sulfuric acid, the resin can be decomposed by recovering the salt and sulfuric acid (in some cases, without recovery), which simplifies the equipment. can.

c) Since both cation exchange resin and anion exchange resin can be decomposed under the same reaction conditions, it is easy to set the conditions.

2) Since the reaction is exothermic, there is no need to forcibly maintain the reaction temperature.

e) of the reaction by monitoring the temperature of the reaction solution.

You can be sure of the ending point.

f) Ferrous sulfate aqueous solution is unstable and not suitable for long-term storage, but ferric sulfate aqueous solution is stable, so vI! Suitable for occasional use.

Representative Patent Attorney Su Yamasa - 591-

Claims (1)

[Scope of Claims] 1. A method for chemically decomposing a radioactive ion exchange resin, which comprises bringing the radioactive ion exchange resin into contact with hydrogen peroxide in an aqueous ferric sulfate solution to oxidize and decompose the resin. 2. A method for chemically decomposing a radioactive ion exchange resin according to claim 1, wherein the oxidation is carried out at room temperature.