JPH0843595A - Method for separating radionuclide from used ion exchange resin - Google Patents

Abstract

PURPOSE:To make it possible to effectively separate radionuclides even though much clad adheres to waste resins, and thereby, to perform the stabilizing treatment of waste resins. CONSTITUTION:Heated nitric acid 12 and waste resins 14 (used ion exchange resins containing radioactive nuclides) are poured into a nuclide separation container 10 and are stirred by a stirrer 16. After the completion of stirring, batch processing operations to draw out waste fluids of nitric acid are repeated many times to separate radionuclides from the used ion exchange resins. In this process, the temperature of nitric acid is set at 80 to 90 deg.C, and it is desirable to stir nitric acid and waste resins for about one hour in a batch processing operation. Especially, it is recommendable to use 2-normal nitric acid, pour the same quantity of it as that of the used ion exchange resins and repeat batch processing operations ten to fifteen times.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for separating a radionuclide from a used ion exchange resin (hereinafter referred to as "waste resin") by a nitric acid immersion / temperature rising stirring method. This method can be used as a measure for reducing the volume of used ion exchange resin generated from a nuclear power plant or the like.

[0002]

2. Description of the Related Art As a part of volume reduction measures for waste resin containing a relatively large amount of γ nuclides generated from nuclear power plants, etc., radioactive nuclides are separated from the waste resin, and the separated resin is incinerated and reduced in volume by an existing incinerator. However, it is considered that the waste liquid containing the radionuclide is concentrated and reduced in volume so that both of them are finally made into stable solidified bodies. As a method for separating the radionuclide from the waste resin, a method has been developed in which about 2N sulfuric acid is continuously passed through a resin tower filled with the waste resin at room temperature.

[0003]

For example, in the case of a new-type converter Fugen power plant, in the reactor coolant purification system (including system decontamination waste resin), the reactor is cooled by boiling light water and the granular ion exchange resin is used. Since the coolant is purified by using, the waste resin of the reactor coolant purification system contains clad radionuclides to the same extent as ionic radionuclides. Generally, in boiling water nuclear power plants, the amount of waste resin clad adhered is large. Therefore, when treating the waste resin generated from these nuclear power plants, it is necessary to efficiently remove the clad component.

However, the method of passing sulfuric acid at room temperature through a resin tower filled with waste resin is not so effective for waste resin having a relatively large amount of clad deposits. Therefore, the amount of sulfuric acid used becomes enormous, and the volume reduction effect becomes small.

An object of the present invention is to provide a method capable of efficiently separating a radionuclide even with a waste resin having a large amount of clad deposits, thereby stabilizing the waste resin.

[0006]

According to the present invention, heated nitric acid and waste resin (a used ion exchange resin containing a radionuclide) are put in a nuclide separation container and stirred, and a nitric acid waste liquid is added after the stirring is completed. Is a method of separating the radionuclide from the used ion-exchange resin by repeating a batch treatment operation for extracting the radioactivity. Here, the temperature of nitric acid is preferably set to 80 to 90 ° C., and stirring is preferably performed for about 1 hour per batch treatment. In particular, 2N nitric acid was used, and its injection amount was made equal to that of the used ion-exchange resin, and the batch processing operation was carried out for 10 to 15
It is good to repeat it once.

[0007]

[Function] By dipping in nitric acid and stirring at elevated temperature, radioactive nuclides can be efficiently separated even with waste resin having a large amount of clad deposits, and the amount of waste liquid generated can be reduced. The DF (decontamination factor) increases as the nitric acid temperature increases. The separation effect improves as the nitric acid concentration increases, but when compared with DF at the same amount of nitric acid used, the case of 2 N is the best.

[0008]

EXAMPLE FIG. 1 is an operation explanatory view of a method for separating radionuclides according to the present invention. The heated nitric acid 12 and the granular waste resin 14 are put in the nuclide separation container 10 and stirred by the stirring device 16. During the stirring process operation, the inside of the nuclide separation container 10 is maintained at a predetermined temperature rising state by the outer heater 18. Then, after the stirring is completed, the nitric acid waste liquid is stored in the waste liquid tank 2
Extract to 0. That is, nitric acid is intermittently injected, a stirring operation is performed, and the waste liquid is intermittently discharged. This batch processing operation is repeated many times. As a result, the radionuclide can be efficiently separated from the waste resin.

The waste resin used in the experiment is the one actually used in the system at the new converter Fugen power plant, and is the waste resin for purifying the reactor used for purifying the primary cooling water of the nuclear reactor. This is what is commonly called granular ion exchange resin,
The particle size is about 0.3 to 1.3 mm. There are powder ion exchange resins finer than that, and no experiment has been conducted therefor, but it is considered that the method of the present invention is applicable in principle. The radionuclide adsorbed on the waste resin is mainly cobalt 60, and the concentration is about 1 × 10 ⁶ Bq / cc-Resi.
n.

In the present invention, the use of nitric acid instead of sulfuric acid or hydrochloric acid has been found to have a higher radionuclide separation efficiency than sulfuric acid, and avoids the adverse effect of chlorine ions derived from hydrochloric acid on structural materials. This is because. As for the concentration of nitric acid, the higher the effect, the more effective it is as a result of the tests of 0.5N, 1N, 2N, and 4N.
Comparing with F, the result that the case of 2 rules was the highest was obtained. From this, the optimum acid concentration is 2N.

The temperature of nitric acid is raised because the efficiency of separation is improved by raising the temperature. The temperature dependence of DF is as shown in FIG. The test conditions are as follows. -Sample: Waste resin for system decontamination-Treatment time: 0.1 hour / batch-2N nitric acid usage: 10 BV In the test at treatment temperature from room temperature to 90 ° C, 90 ° C is most effective, and room temperature There is a difference of about 10 times or more. Therefore, especially 80-90 degreeC is preferable. The reason why the upper limit is set to 90 ° C is that treatment at the boiling point (86 ° C with concentrated nitric acid) is a good idea in terms of system configuration.

Regarding the separation treatment method, a method using ultrasonic cleaning in combination and a continuous liquid passing method were also examined.
It was found that the nitric acid dipping in which an equal amount of waste resin and 2N nitric acid are stirred per batch was performed. The temperature rising stirring method (batch processing time: 1 hour / batch) was found to be most suitable. The stirrer used in the experiment is of a type that is stirred by a blade (two blades), and the rotation speed is 500 rpm. This value of 500 rpm is
It is almost the maximum number of rotations at which the liquid does not scatter.

As a result of separating the radionuclide from the actual waste resin by the separation method obtained from the above basic experimental results, FIG.
As shown in Fig. 2, the concentration of cobalt 60 remaining in the resin was adjusted to 7 times with 2N nitric acid which was 10 times the volume of the resin.
kBq / cc-Resin could be reduced to below, and the desired target was achieved. The test conditions are: treatment temperature: 90 ° C. treatment time: 1 hour / batch.

By the way, as a result of comparison between the conventional normal temperature continuous liquid flow method and the immersion / temperature rising stirring method of the present invention, the treatment method using 2N nitric acid (provided that a laboratory level with several ml of waste resin is used). Test result), the conventional method was able to obtain only 12 with DF even when 50 times the amount of waste resin was passed, but with the method of the present invention, DF1 was obtained with 7 to 9 times the amount.
A value of 00 or more was obtained. However, in the scaled-up test, the treatment performance is slightly deteriorated, so that 10 to 15 times the amount of the waste resin is actually required. However, it can be seen that the method of the present invention nevertheless requires a significantly small amount of waste liquid.

FIG. 4 shows an example of a radionuclide separating apparatus for carrying out the method of the present invention. Nuclide separation container 30
To supply the waste resin. 2 in the nitric acid storage tank 32
Normalized nitric acid is heated to 80 to 90 ° C. through the heater 34 and injected into the nuclide separation container 30. The injection amount is the same as the waste resin. A heater 36 is provided outside the nuclide separation container 30.
To keep warm throughout the batch processing operation. Here, when the nitric acid is injected, the heater 34 preheats only the heater 36 of the nuclide separation container 30 to reduce the temperature of nitric acid at room temperature to 8%.
This is because it takes too long to raise the temperature to 0 to 90 ° C. The nuclide separation container 30 is provided with a stirrer 38, and the stirring operation is continued for 1 hour per batch, and the temperature is kept at 80 to 90 ° C. by the heater 36 during that period. The generated gas is processed by a gas processing system.

After completion of one batch process (stirring process for 1 hour), the waste liquid in the nuclide separation container 30 is extracted and sent to the waste liquid tank 40. Then, again, the nitric acid from the nitric acid storage tank 32 is heated to 80 to 90 ° C. by the heater 34 and supplied into the nuclide separation container 30, and the stirring operation is performed. This operation 10
Repeat 15 times. Waste resin after processing is stored in the resin storage tank 4
The waste liquid in the waste liquid storage tank 40 is stored in the waste liquid storage tank 40 and processed by the waste liquid processing system. Filters 44 and 45, which have finer meshes than the granular resin, are installed at the bottoms of the nuclide separation container 30 and the resin storage tank 42, and the treated resin is rotated in the clockwise direction by starting the pump 46. By circulating the liquid, the liquid can be transferred from the nuclide separation container 30 to the resin storage tank 42.

[0017]

INDUSTRIAL APPLICABILITY As described above, according to the present invention, the heated nitric acid and the used ion-exchange resin containing the radionuclide are put in the nuclide separation container and stirred, and the nitric acid waste liquid is extracted after completion of the stirring. Because it is a method to repeat the operation many times,
As a result, the radionuclide can be efficiently separated from the waste resin having a relatively large amount of clad deposits, and the amount of nitric acid used can be small. By this method of separating radionuclides, when treating a waste resin containing a relatively large amount of γ-nuclide, the γ-nuclide is separated from the waste resin, the separated resin is incinerated and volume-reduced, and the waste liquid is concentrated and volume-reduced. Will be able to effectively implement the disposal method to make stable solidified bodies.

[Brief description of drawings]

FIG. 1 is an operation explanatory view of a method for separating a radionuclide according to the present invention.

FIG. 2 is a graph showing the temperature dependence of DF.

FIG. 3 is a graph showing the results of a radionuclide separation test.

FIG. 4 is an explanatory view showing an example of a radionuclide separating apparatus for carrying out the method of the present invention.

[Explanation of symbols]

 10 Nuclide Separation Container 12 Nitric Acid 14 Waste Resin 16 Stirrer 18 Heater 20 Waste Liquid Tank

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Yuichi Tsukamoto Inventor Yuichi Tsukamoto 3 Myojin-cho, Tsuruga City, Fukui Prefecture Power Reactor / Nuclear Fuel Development Corp. New Converter Reactor Fugen Power Plant (72) Inventor Mitsumori Shimizu Myojin-cho, Tsuruga City, Fukui Prefecture 3 Power Reactor / Nuclear Fuel Development Agency New Converter Reactor Fugen Power Station Premises Incorporated Company Tsuruga Nuclear Service Office

Claims (4)

[Claims] 1. A batch treatment operation in which a heated nitric acid and a used ion-exchange resin containing a radionuclide are put in a nuclide separation vessel and stirred, and a nitric acid waste liquid is extracted after the stirring is repeated many times. Method for separating radionuclides from used ion-exchange resins. 2. The separation method according to claim 1, wherein nitric acid at 80 to 90 ° C. is used and stirring is performed for about 1 hour per batch treatment. 3. The separation method according to claim 2, wherein 2N nitric acid is used and the injection amount thereof is the same as that of the used ion exchange resin. 4. The separation method according to claim 3, wherein the batch processing operation is repeated 10 to 15 times.