JP2992377B2 - Treatment of radioactive liquid waste - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating radioactive waste liquid generated from nuclear facilities, and more particularly to a method for treating low-level radioactive waste liquid having low radioactivity such as washing water for washing clothes, hand washing and shower water.

[0002]

2. Description of the Related Art At a nuclear facility, particularly a nuclear power plant, waste water such as washing water for washing clothes used by workers, hand washing, and showers is generated. Such wastewater has a very low radioactivity concentration, contains a lot of suspended components such as detergent components, lint, hair and dust, and has a high chemical oxygen demand (COD) due to detergent components, shampoos and the like. In the case of treating these waste liquids, conventionally, after removing large waste such as lint with a strainer, the radioactivity is measured, and it is confirmed that the radioactivity is less than the specified concentration and released to the environment. .

[0003]

However, in this method, it is almost impossible to remove fine suspended suspended substances in the waste liquid, substances such as detergents, oils, etc., which cause chemical oxygen demand. Not preferred for conservation. Therefore, a treatment method for removing substances such as a fine suspended suspended substance and a detergent which is a source of chemical oxygen demand contained in these wastewaters was attempted.

As a method for removing suspended suspended substances in wastewater, there are a filtration method using a filter medium such as diatomaceous earth, a hollow fiber membrane filter, and a method using a ceramic filter. As a method for removing detergents and the like, there is a method using activated carbon. These methods have the following disadvantages.

[0005] In the method of pre-coating suspended suspended solids with diatomaceous earth, the used diatomaceous earth is slightly discarded because of the presence of radioactivity, as in general industry. Since diatomaceous earth is an inorganic substance, it cannot be incinerated. On the other hand, non-filter material type filters, such as hollow fiber membrane filters and ceramic filters, are not suitable because of the nature of these wastewaters that the processing capacity is significantly reduced due to clogging during filtration.

[0006] As a method of removing a detergent, which is a main substance of the chemical oxygen demand, adsorption by activated carbon is generally known. However, this method of removing with activated carbon requires regeneration and replacement of the activated carbon when the adsorbing power of the activated carbon is reduced. There is a problem that the regeneration and replacement of activated carbon is not as easy as in general industry.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and provides a method for treating a radioactive waste liquid capable of efficiently removing suspended suspended substances and chemical oxygen demanding substances from a low-level radioactive waste liquid. It is in.

[0008]

According to the present invention, a low-level radioactive waste liquid such as a washing waste liquid or a shower drain waste liquid generated in a nuclear facility is passed through a filter filled with polymer fibers as a filter medium. After removing suspended suspended substances in the radioactive liquid waste, the filtrate is passed through an electrolysis tank to remove chemical oxygen demanding substances.

[0009]

[Function] Suspended suspended substances in low-level radioactive waste liquid are easily captured by a polymer fiber filter medium, and substances that mainly cause chemical oxygen demand such as detergents are easily decomposed by electrolysis, Oxygen demand is reduced.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method for treating radioactive waste liquid according to the present invention will be described with reference to FIG. FIG. 1 shows a system diagram of an apparatus for carrying out the method of the present invention.

In FIG. 1, reference numeral 1 denotes a liquid supply tank, and a low level radioactive test waste liquid 2 is stored in the liquid supply tank 1. At the bottom of the supply tank 1 is connected a waste liquid outlet pipe 3, the waste outlet pipe 3 is connected to the pump 4 via a valve V _1. A waste liquid supply pipe 6 connected to a filter 5 filled with polymer fibers as a filter medium is connected to the discharge side of the pump 4. The outlet side of the filter 5 supplies the filtrate filtrate transport pipe 8 is connected via a valve V ₂ on the electrolytic cell 7. A description will be given of the result of performing the purification treatment of the radioactive waste liquid using the apparatus having the above configuration. As the radioactive waste liquid, a washing waste liquid discharged from a nuclear power plant is used as a test waste liquid, and the composition of the test waste liquid is as shown in Table 1.

[0012]

[Table 1]

The test waste liquid having the above composition is supplied to the liquid supply tank 1, and the pump 4 is operated to open the valves V ₁ and V ₂ ,
Water is passed through the filter 5 and the electrolysis tank 7. That is, the test waste liquid 2 in the liquid supply tank 1 is discharged by the pump 4
And, it flows into the filter 5 through the waste liquid supply pipe 6. The filtrate filtered by the filter 5 flows into the electrolysis tank 7 through the filtrate transport pipe 8 to be electrolyzed. Electrolyzed effluent is discharged from the discharge pipe outlet S _2. The decomposition conditions in the electrolysis tank 7 are as shown in Table 2.

[0014]

[Table 2] Table 3 shows the results obtained by measuring the suspended suspended solids and the chemical oxygen demand concentration at the outlet S ₁ of the filter 5 and the outlet S ₂ of the electrolysis tank 7 by the above operation.

[0015]

[Table 3]

As is clear from Tables 1 and 3, the suspended suspended substance was reduced from 40 ppm in the feed tank 1 to 6 ppm at the outlet S ₁ of the filter 5. The chemical oxygen demand (COD) of was 48ppm in the liquid supply tank 1, it is observed to decrease to 4ppm in outlet S ₂ of the electrolysis tank 7. Thus, the present invention can reduce suspended suspended solids in the filter 5 and decompose the chemical oxygen demand in the electrolysis tank 7.

[0017]

According to the present invention, the treatment of low-level radioactive liquid waste having a very low radioactivity concentration and a relatively high chemical oxygen demand concentration, such as washing water, hand washing, and showers, of clothes generated in a nuclear facility can be performed. It can be done easily.

[Brief description of the drawings]

FIG. 1 is a system diagram showing an example of an apparatus for explaining a method for treating a radioactive waste liquid according to the present invention.

[Explanation of symbols]

1 ... supply tank, 2 ... test waste liquid, 3 ... waste liquid outflow pipe, 4 ...
Pump, 5 ... filter, 6 ... waste supply pipe, 7 ... electrolytic cell, 8 ... filtrate transport tube, V _1, V ₂ ... valve.

Claims (1)

(57) [Claims] 1. A low-level radioactive waste liquid such as a washing waste liquid or a shower drain waste liquid generated in a nuclear facility is passed through a filter filled with polymer fibers as a filter medium to form a suspended suspension in the radioactive waste liquid. A method for treating a radioactive liquid waste, comprising removing a substance and then passing the filtrate through an electrolysis tank to remove a chemical oxygen demanding substance.