JPS6262299A - Method of processing 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 (Industrial Application Field) The present invention relates to a method for stabilizing used ion exchange resins stored in nuclear facilities.

(Prior Art) As a method for disposing of used ion exchange resins (hereinafter simply referred to as @fat), various techniques have been proposed, such as those described below, although there are still no examples of long-term application.

(13 Incineration method: This is a method of incinerating resin, but if the radioactivity level contained in the resin is high, the amount of radioactivity contained in the combustion exhaust gas will also increase, so excessive radioactivity removal performance is required of the exhaust gas treatment equipment. In other words, the exhaust gas treatment equipment becomes complicated and large-scale.Furthermore, the radioactive concentration of the incinerated ash is high, making it difficult to handle it.

(2) Pyrolysis method; thermal decomposition at high temperature in an inert atmosphere,
This method then combusts the cracked gas.

This method has the advantage of producing less dust compared to the incineration method, but has the disadvantage of requiring an extra thermal decomposition step, and is similar to the combustion method in that the radioactivity concentration of the product is high.

(3) Chemical decomposition method: This method involves acid decomposing the resin through a chemical reaction with chemicals, but since strong acids and oxidizing agents are handled at high temperatures, corrosion of the equipment constituent materials becomes a problem. Furthermore, the radioactivity level is high and maintenance is difficult.

(4) Direct assimilation method: This is a method in which resin is directly solidified with cement, asphalt, or plastic, but because the resin has a high radioactivity level, the resin suffers radiation deterioration during long-term storage, resulting in a decrease in - Damage to the solidified material due to the generation of gas,
This will eventually lead to damage to the container (drum).

(Problems to be Solved by the Invention) The present invention is designed to elute (separate) radioactive substances adsorbed to the resin when acid decomposing a resin at a relatively high level.
By doing so, the resin can be treated as a low-level substance, and when the resin is subjected to acid decomposition, the contamination level of the equipment can be kept low, maintenance is easier, and operation is improved, while the resin can be treated as a low-level substance. The separated nuclides pass through a diffusion dialysis tank and are concentrated to provide a method for treating radioactive ion exchange resins that can be solidified.

(Means for Solving the Problems) In the treatment of radioactive ion exchange resins, the present invention uses an eluent (alkaline solution or acid solution) to remove radionuclides with medium to long half-lives that are adsorbed on the radioactive ion exchange resin. The ion exchange resin from which the nuclide was eluted was treated by an acid decomposition method, and the eluent from which the nuclide was eluted was passed through a diffusion dialysis tank to form a radioactive nuclear mecondensate and a regenerated eluent. This is a method for treating radioactive ion exchange resin, which is characterized by separating the resin, reusing the latter in the system, and concentrating and solidifying the former.

That is, in the present invention, nuclides with medium to long half-lives (Co-60, 0s-434, -137, 5r-
90, etc.) is eluted from the resin using Ha+, Ni+, or Cod ions in an alkaline solution such as NaOH, KOH or an acid solution such as H2S04, the resin can be used as a low-level radioactive material. This makes it possible to maintain low contamination levels in conventional acid decomposition equipment and facilitate maintenance.

In addition, the alkaline solution or acid solution used for elution is passed through a diffusion dialysis tank, and the nuclide in the solution is separated into a concentrated nuclide solution and a regenerated eluent, and the latter is used again to elute the nuclide from the resin. However, the former is concentrated and solidified. As a result, secondary waste can also be reduced.

Semipermeable membranes are generally used as membranes in diffusion dialysis tanks, but when the eluent is an acid solution, anion exchange membranes such as Selemion, Neocepta, and Unirex (all trade names) are used. It is preferable to use

Hereinafter, one embodiment of the present invention will be described.

FIG. 1 shows a flow for implementing the method of the present invention.

First, a fixed amount of resin is taken out from the waste resin storage tank 1 (in this process, 0.25 door 37 times) and filled into the resin processing tank 2. Next, pump 4 H2S04 at a constant concentration (approximately 9%).
) Pour the liquid through. At this time, the nuclides are eluted in the resin treatment tank 2, and the cod is adsorbed. (H2S04 is consumed).

A diffusion dialysis tank 3 is installed downstream of this tank 2, and an anion exchange membrane 3' is provided inside the tank 3 to divide the cypress 3 into a left ventricle and a right ventricle. Now, if the eluent containing nuclides is passed in an upward flow to the left chamber, while pure water is passed in a downward flow to the cloth chamber, during this time, in the cypress 3, the HBO in the eluent is mixed with cod and SO. It dissociates into the SO knee, passes through the anion exchange membrane 3', and moves to the right ventricle. On the other hand, the eluted nuclides (Cjo”, CjB+
) are ionically repulsed by each other and do not move to the right ventricle. From this, the acid (H2S04) and the nuclide can be separated. The recovered acid is used again as an eluent.

By separating and recovering the nuclide and the eluent in this way, it is possible to reduce the amount of secondary waste. The liquid containing the nuclide is concentrated in a small evaporator 6 and then directly converted into an assimilate 8.

On the other hand, the resin from which the radionuclides have been extracted is led to the acid decomposition tank 5. Here, H2O2-Fe system or H2BO
The resin is chemically decomposed with a chemical solution such as 3-HNO. Although this decomposed liquid contains some undecomposed substances, its radioactivity level is sufficiently low and is therefore treated with the existing waste liquid treatment system. After passing through the existing evaporator 9, it is led to the solidification device 10. By performing this operation, two types of solidified bodies are created: the assimilated body of the nuclide and the solidified body from the existing solidification equipment, which can also be used for separate management.

General acid decomposition conditions are shown in the table below.

However, method A: H2So4+ HNO3 mixture B:
H2SO4 + H2O2 mixture C: H2O + H2O2 (Fe catalyst) mixture Above, we have explained the case where acid (H2S04) is used as the eluent, but when using alkali as the eluent, a semipermeable membrane is used as the diaphragm of the diffusion dialysis tank. Almost the same result can be obtained by doing this.

(Effect of the invention) Because the nuclide is removed from the resin, 1) The dose of acid decomposition equipment can be kept low.

2) Therefore, maintenance of the device becomes easier, which in turn leads to improved operability.

3) Also, the solidified material can be divided into high and low levels, and can be used for separate management.

[Brief explanation of the drawing]

FIG. 1 shows a 70- for carrying out the method of the invention. Among the sub-agents: 1) Akira Sub-agent Ryo Hagi Hara - Sub-agent Atsuo Annishi

Claims (1)

[Claims] When treating radioactive ion exchange resins, radionuclides with medium and long half-lives adsorbed on the radioactive ion exchange resins are eluted using an eluent consisting of an alkaline solution or an acid solution.
The ion exchange resin that has eluted the nuclide is treated with an acid decomposition method, and the eluate that has eluted the nuclide is passed through a diffusion dialysis tank and separated into a radionuclide concentrate and a regenerated eluate, with the latter being reused in the system. However, the former is a method for processing radioactive ion exchange resin, which is characterized by concentration and solidification.