JPS6151598A - Method of reducing radioactive waste - 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 [Field of Industrial Application] The present invention relates to a method for regenerating an ion exchange resin in an ion exchange device containing radioactive substances.

[Prior art]

Conventionally, for example, in a condensate purification system in a nuclear power plant, that is, a condensate desalination device, ion exchange was performed at a point when the ion load in the ion exchange resin was extremely low in order to prevent ore and seawater leakage and to ensure the purity of the outlet water. As the resin is being regenerated, unreacted chemicals (caustic soda or sulfuric acid) remain in the regenerated waste liquid that is generated at this time in an amount of 90% or more of the amount passed.

The recycled waste liquid of the ion exchange resin containing unreacted chemicals is sent as is to the waste treatment system, where it is evaporated and concentrated and finally solidified as sodium sulfate in a drum with asphalt or cement. However, these solidified wastes are radioactive and cannot be easily disposed of, so they are currently accumulating inside power plants, and the disposal of these radioactive wastes is not an environmental issue. This is one of the important issues.

[definition of invention]

The present invention is a method for regenerating an ion exchange resin obtained by ion-exchanging a liquid containing radioactive ions, in which approximately 1/2 the amount of chemical solution passed in the first half of the previous ion exchange resin f') was used in the second half of half an hour. This method of reducing radioactive waste during ion exchange resin regeneration is characterized by using a newly prepared chemical solution for approximately 1/2 volume of the chemical solution passed through the back half of the heel.

Since the disposal method of radioactive waste has become a serious social issue, the people of Kienori and others believe that even if the disposal method cannot be completely solved, if the amount of waste to be disposed of is reduced,
Is the recycled waste liquid discharged during ion exchange resin regeneration because it can reduce the storage volume of waste? The present invention was developed while conducting various studies on ways to reduce this.

The present invention reduces the amount of radioactive waste accumulated as a solidified product by reducing the amount of unreacted chemicals in the regeneration waste liquid that must be discarded during the regeneration of ion conversion resins.

The ion load during normal operation at nuclear power plants, etc. is
The demineralization tower is operated at 45000 fiθ/crrcm per tower, and therefore the ion load on the ion exchange resin must be small during the regeneration of the ion exchange resin. Usually, the waste of the regeneration agent in 8 H2BO3 and 4 H Naou is small, and a large amount of unreacted agent, ie sulfuric acid or caustic powder, is present in the regeneration effluent.

The following table shows the relationship between the amount of drug in the regeneration drug solution (drug passing amount) and the amount of unreacted drug present in the regeneration waste liquid during normal ion exchange resin regeneration.

As shown in the table above, the regenerated waste liquid contains a large amount of unreacted regenerant, so it is conceivable that the regenerated waste liquid 1&: may be used repeatedly, but the K in the regenerated waste liquid contains
In addition, the regeneration level of the ion exchange resin will not only decrease, but also the regeneration level of the resin will vary as the Irs or Ct' in the regeneration solution becomes concentrated when used repeatedly. This is not preferable in terms of desalting operations.

Therefore, when the ion exchange resin to be regenerated was treated with the recycled waste liquid and then treated with the newly prepared regenerating liquid, when a relatively small amount of the newly prepared regenerating liquid was used, the regeneration level of the ion exchange resin was completely different from that in the conventional method. I found scales that regenerate to a similar level.

In order to maintain the regeneration level of the ion exchange resin at a constant value and perform continuous regeneration, the first half of the regeneration must be preceded by the "full regeneration" process used in the second half of the previous ion exchange resin regeneration. Regeneration is performed using a chemical solution corresponding to about 1/2 of the liquid, and then regeneration is performed using a newly prepared chemical solution corresponding to about 1/2 of the total regeneration solution. By discarding only the chemical solution used in the first half and storing the newly prepared chemical solution used in the second half for use in the next regeneration, the regeneration level of the ion exchange resin can be maintained at the same level as the conventional method. However, f[tl of the regenerated waste liquid to be discarded can be reduced to about 1/2 of that of the conventional method.

EXAMPLE An ion exchange resin regeneration treatment experiment was conducted using a model plant of a condensate desalination equipment at a nuclear power plant.

The mixed ion exchange resin to be regenerated is first led from the demineralization tower to the cation exchange resin regeneration tower, separated into negative and positive ion exchange resin layers according to a conventional method, and then the anion exchange resin is led to the anion exchange resin regeneration tower. Both ion exchange resins were then regenerated, respectively.

First, after washing the cation exchange resin with water under reverse conditions, it was washed with H, So4 regenerating solution in an amount equivalent to about 1/2 of the total amount of regenerating solution used in the latter half of the previous cation exchange resin regeneration. process,
Then, the second half was treated with a freshly prepared H2So4 regenerating solution in an amount equivalent to about 1/2 of the total regenerating solution. In this case, the recycled waste liquid used in the first half was sent to the waste treatment line, and the recycled liquid used in the second half was stored in a storage tank for use in the first half of the next cation exchange resin regeneration.

For anion exchange resin, 5-fiber NaO is also used as a regenerating liquid.
It was regenerated in the same manner as the cation exchange resin regeneration described above except that H water bath solution was used. The regenerated both ion exchange resins were mixed according to a conventional method, temporarily stored, and then sent to a desalination tower for desalination of condensate.

The regeneration level of ion exchange cutting by the above method is exactly the same as when using regeneration 'tL with newly adjusted total and discharge, and under exactly the same conditions as regeneration using the conventional method except for the regeneration method. During the operation, there was no difference in the quality of the condensate or anything else compared to the conventional method.

〔Effect of the invention〕

In the present invention, when regenerating the ion exchange resin, the regeneration level is the same as that of the conventional method by providing a storage tank for regeneration liquid equivalent to about 1/2 of the total amount of regeneration liquid used in the latter half and piping to the nuclide. It becomes possible to reduce the amount of regenerated waste liquid to about 1/2 of that of the conventional method while maintaining the regenerated waste liquid, and therefore, it becomes possible to reduce the volume when solidifying and storing the regenerated waste liquid to 1/2.

Claims (1)

[Claims] 1. In a method for regenerating an ion-exchange resin obtained by ion-exchanging a liquid containing radioactive ions, about 1/2
An ion exchange method characterized by using the chemical solution used in the second half of the previous ion exchange resin regeneration for two amounts of the chemical solution, and using the newly prepared chemical solution for about half the amount of the chemical solution passed in the second half. Method for reducing radioactive waste during resin regeneration. 2. The 1/2 amount of the chemical solution passed in the first half is discarded, and the approximately 1/2 amount of the chemical solution passed in the second half is temporarily stored for use in the first half of the next ion exchange resin regeneration. range 1
Described radioactive waste reduction method.