JP3194549B2 - 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 low-level radioactive liquid waste (aqueous solution) or concentrated liquid waste generated in a controlled area such as a nuclear power plant that handles radioactive materials. The present invention relates to a treatment method for converting radioactive laundry waste liquid or its concentrated waste liquid generated after washing working clothes or protective gear worn by the company into a solid matter that can be easily handled and that can be incinerated.

[0002]

2. Description of the Related Art For radioactive waste generated from nuclear facilities, development of volume reduction processing technology according to the form has been promoted, and a part thereof has already been put into practical use.

For example, radioactive waste liquid among these radioactive wastes is separated and collected according to its properties, and the following processing is performed. A waste liquid having a low soluble salt content is subjected to a filtration treatment using a hollow fiber membrane filter or the like and a desalination treatment using an ion exchange resin, and the treated water is used as makeup water in a nuclear power plant. Further, radioactive waste liquid unsuitable for desalination treatment and regenerated waste liquid generated during the regeneration treatment of the above-mentioned ion exchange resin were subjected to evaporation and concentration in a concentrator, and the condensed water generated was subjected to desalination treatment as necessary. It is also reused as make-up water in nuclear power plants. On the other hand, the concentrated waste liquid remaining in the concentrator is temporarily stored and, after the radioactivity is attenuated, dried and pulverized by a vertical thin film dryer.

[0004] As for radioactive waste, combustible miscellaneous solid waste such as paper and cloth generated during work in a controlled area has been put into practical use by a combustion treatment technique using an incinerator.

Further, the radioactive waste processed into powder or pellets generated by the above-mentioned treatment is mixed with a solidifying agent such as cement or plastic in a solidified container and solidified in preparation for final disposal. Has been established.

On the other hand, as a method for cleaning work clothes or protective gear worn by workers in a controlled area where radioactive materials such as a nuclear power plant is handled, there is a dry cleaning method using a solvent such as Freon. With the dry cleaning of the work clothes and the like, radioactive waste liquid containing a solvent, a detergent, and dirt comes out. As a method for treating the remaining radioactive sludge obtained by recovering and recycling the solvent from the waste liquid by distillation, Japanese Patent Laid-Open No.
JP-A-79297 proposes a processing method in which a gelling agent is added to the radioactive sludge to convert the radioactive sludge into a gel-like semi-solid having no fluidity. As the gelling material, a 10% to 20% solution of sibensilden D-sorbitol in N or the like is used. N-dimethylformamide; N-dimethylacetamide, dimethylsulfoxide and the like are used.

[0007]

As a method of cleaning working clothes or protective gear worn by workers in a controlled area handling radioactive materials such as a nuclear power plant, there is a dry cleaning method using a solvent such as chlorofluorocarbon. Has been described above.
However, in response to global environmental problems such as depletion of the ozone layer, the use of detergents for washing and washing has been reconsidered as the use of CFCs has become more restricted. However, in the case of this washing and washing method, the generated washing waste liquid is an extremely low-level radioactive waste liquid.However, since it is necessary to minimize the radioactivity released to the environment outside a nuclear facility, the above-described conventional treatment of the radioactive waste liquid is performed. The technology has to be applied, and the installation of the water treatment apparatus and the vertical thin-film dryer has a drawback that a large facility cost is required.

When the conventional radioactive waste liquid treatment technology is applied to radioactive washing waste liquid or its concentrated waste liquid, when powder is dried by a vertical thin-film dryer, detergent, oil and salt, etc. are contained in the waste liquid. There are the following problems from inclusion.

(1) When the radioactive washing waste liquid or its concentrated waste liquid is dried and powdered by a vertical thin film dryer, foaming occurs in the dryer, so that a special operation is required. For this reason, mixing with ordinary low-level radioactive waste liquid other than the radioactive laundry waste liquid cannot be performed, so that a dedicated powder drying facility is required.

(2) When the dried powder obtained by treating the radioactive laundry waste liquid is solidified with cement or plastic for final disposal, it is considered that organic matter such as detergent remains in the solidified body. Therefore, if stored for a long period of time, it may be decomposed and decomposed, and may not meet the conditions for final disposal.

[0011] As described above, when a washing and washing method using a detergent is used to wash work clothes or protective gear worn by workers in a controlled area of a radioactive material such as a nuclear power plant, an extremely low level is generated. The problem was how to easily treat the radioactive liquid waste.

On the other hand, the treatment method described in Japanese Patent Application Laid-Open No. 60-79297 is not intended for radioactive washing waste liquid generated by a washing washing method. Further, when the gel-like semi-solid is incinerated, N.I. N-dimethylformamide; N-dimethylacetamide, dimethylsulfoxide, and the like generate NOx, which is a harmful substance, and thus have a problem of polluting the environment.

An object of the present invention is to provide a method for treating a radioactive waste liquid which is easy to handle and can be incinerated by converting the radioactive waste liquid into a solidified substance, and which does not pollute the environment even when incinerated. It is to be.

[0014]

In order to achieve the above-mentioned object, the treatment method of the present invention is used by a worker in a nuclear facility.
That occur after washing working clothing or personal protective equipment
The radioactive waste liquid or the concentrated waste liquid is mixed with a water absorbing material that is flammable and does not generate harmful substances even when burned, and the water is absorbed into the water absorbing material to convert the radioactive waste liquid into a solidified substance. Convert and convert this
To incinerate .

In the above treatment method, the water absorbing material be burned and flammable generates no harmful substances, acrylic acid-vinyl alcohol copolymer, acrylic acid polymers, in pump I in salt acrylate graft There is a polymer moisture absorber of any of a polymerized starch-based polymer and a cellulose-based polymer obtained by graft-polymerizing an acrylate or the like to carboxyl cellulose or the like.

Further , in order to achieve the above object, the present invention
In the treatment method, work clothes worn by workers at nuclear facilities
Radioactive washing waste liquid generated after washing of protective equipment
Alternatively, the concentrated waste liquid is converted into polyethylene oxide
Mix and stir with adult to form modified polyethylene oxide
Radioactive waste by absorbing water in radioactive waste liquid
The liquid is converted to a solid and the converted is incinerated .

[0017]

[0018]

According to the present invention, radioactivity utilizing the water retention of a water absorbing material is used .
This is a method of solidifying the washing waste liquid or its concentrated waste liquid . It
By mixing and stirring the al radioactive waste and moisture absorbing material,
The water absorbing material swells in a few minutes while absorbing the water in the radioactive liquid waste. At this time, the present inventors have found that the water absorbing material has an advantageous effect of also capturing dissolved components in the radioactive waste liquid. The thus obtained swollen water-absorbing material having no free water is in the form of an easily solidified substance, and the radioactive waste liquid is converted into the solidified substance.

At room temperature, the obtained solidified product maintains a stable state without releasing the retained radioactive waste liquid against external impact or pressure. As a result, it is possible to fill a container such as a drum can, and handling such as subsequent transportation and storage in a warehouse becomes easy.

The obtained solidified product is finally incinerated. At this time, water, which is a large part of the volume, is removed, and the water absorbing material itself burns. It becomes possible. Further, since the moisture absorbing material does not generate harmful substances when burned, it does not pollute the environment. Moreover, after incineration, a mineralized residue is obtained, so that a treatment suitable for final disposal becomes possible.

In order to obtain a solid without free moisture,
It is important how to set the optimal mixing ratio between the radioactive liquid waste and the water absorbing material. Of course, if the proportion of the water absorbing material is increased, it is possible to obtain a solid without free moisture.However, since the amount of the water absorbing material increases, the cost increases, and the solidified material generated is increased. The disadvantage is that the volume increases. The optimal mixing ratio of radioactive liquid waste and water absorbing material is
Although it depends on the type of the water absorbing material and the component and concentration of the waste liquid, it can be easily obtained experimentally.
As a water absorbing material, as an example, when using a high molecular weight water absorbing material, for example, a poly (sodium acrylate) polymer among acrylic acid polymers, for a waste liquid close to fresh water, the mixing ratio of the radioactive waste liquid and the water absorbing material is adjusted. The amount can be about 1000 times, but it is possible to obtain a solidified product free of free water at a ratio of 10 to 100 times with respect to radioactive washing waste liquid containing detergent, oil and salt, and the like.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. FIG. 1 shows a system configuration of a solidification processing apparatus that employs the present invention for processing radioactive washing waste liquid in a nuclear power plant.

In FIG. 1, radioactive washing waste liquid generated in a nuclear power plant is first collected in a collecting tank 1, and thereafter, the waste liquid is treated batchwise. The collected radioactive laundry waste liquid is passed through an activated carbon filter 2 to remove non-soluble solids in the waste liquid and a surfactant contained in the detergent, and is guided to the concentration device 3. The radioactive washing waste liquid is heated and evaporated by the concentrating device 3, the generated steam is cooled by the condenser 4, and the condensed water is collected in the condensed water collecting tank 5, and then subjected to desalination treatment or the like as necessary, and Reused as make-up water in the power plant. On the other hand, the concentrated waste liquid of the radioactive washing waste liquid remaining in the concentration device 3 is collected in the concentrated waste liquid tank 6. The concentrated waste liquid 8 and a water absorbing material 9 made of, for example, a sodium polyacrylate polymer among acrylic acid polymers
Are respectively metered and supplied to the mixing tank 10 and then stirred and mixed. After confirming that the water in the mixing tank 10 has been exhausted, the solidified material 11 is filled in a drum 12.

The filled drum 12 is capped, transported to a solid waste storage, and stored. This solidified product is finally incinerated in an incinerator to reduce the volume, and the residue after incineration is solidified by a solidifying agent such as cement or plastic for final storage, enabling a significant volume reduction. .

FIG. 2 is a detailed view of a portion in which radioactive laundry waste liquid and a water absorbent are mixed and temporarily stored in a drum.

The radioactive washing waste liquid or the concentrated waste liquid 8 is supplied to the mixing tank 10 by the supply pump 13. On the other hand, a water absorbing material 9 made of a sodium polyacrylate polymer or the like is supplied from a hopper 7 to a mixing tank 10. The supply amounts of the radioactive laundry waste liquid or the concentrated waste liquid 8 and the water absorbing material 9 are measured by the flow meter 14 and the measuring device 15, respectively, and are controlled so that the mixing ratio between the waste liquid and the water absorbing material is optimized. In the mixing tank 10, the waste liquid and the water absorbing material are stirred and mixed for several minutes so that the water absorption is promoted and uniform. Then, after confirming that the water in the mixing tank has been exhausted, the electric shutter-type opening / closing valve 16 is opened, and the obtained simple-shaped solid product 11 is filled into the drum 12 from below the mixing tank. The drum 12 in which the solidified material 11 is completely filled is capped, transported to a solid waste storage, and stored.

According to the present embodiment configured as described above,
It becomes possible to solidify radioactive laundry waste liquid that is not suitable for drying into powder from radioactive waste liquid. That is, the radioactive waste liquid is converted into a solidified substance having no moisture, so that the drum 12
Can be handled in the same manner as other combustible solid waste generated in nuclear power plants, making transport and storage in solid waste storage easier. Become.

As the water absorbing material, for example, a combustible substance such as a sodium polyacrylate polymer of an acrylic acid polymer which does not generate harmful substances such as NOx when burned is used. As a result, water occupying most of the volume is removed, and the water absorbing material itself burns without generating harmful substances, so that the volume can be significantly reduced without polluting the environment. Moreover, after incineration, a mineralized residue is obtained, so that a treatment suitable for final disposal becomes possible.

In view of the whole system, the dryer required in the prior art is not required, so that the initial equipment cost can be reduced. Further, the amount of waste generated at the stage where the radioactive waste liquid is subjected to the solidification treatment according to the present embodiment is larger than that of the powder drying treatment of the prior art, but since the incineration treatment described above is possible, the final amount is small. Specifically, it is possible to achieve the same volume reduction as in the powder drying treatment.

Although the above embodiment is directed to the treatment of radioactive waste liquid in a nuclear power plant, it is natural that the same treatment as described above can be applied to other radioactive waste liquid.

[0031]

According to the present invention, since a such infusible radioactive laundry waste suitable for drying powdered of radioactive waste into a free solidified moisture, be handled and filled in containers drums etc. It becomes possible, and handling such as transportation and storage in a solid waste storage is facilitated.

Further, since a substance which is flammable and does not generate harmful substances even when burned is used as the water absorbing material, the volume can be significantly reduced without polluting the environment by burning in an incinerator. . Moreover, after incineration, a mineralized residue is obtained, so that a treatment suitable for final disposal becomes possible.

Further, since the dryer required in the prior art is not required, the initial equipment cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a method of treating a radioactive waste liquid according to an embodiment of the present invention.
FIG. 1 is a diagram showing a system configuration of a processing apparatus that performs the processing .

FIG. 2 is a detailed view of a main part of the processing apparatus shown in FIG.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Akihiro Komatsu 3-2-1, Sachimachi, Hitachi City, Ibaraki Prefecture Inside Hitachi Engineering Co., Ltd. (56) References JP-A-62-160187 (JP, A) JP-A Sho 63-59385 (JP, A) JP-A-52-44399 (JP, A) JP-A-62-172299 (JP, A) JP-A-4-239087 (JP, A) JP-A-52-37699 (JP, A) A) JP-A-53-62100 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C02F 1/00 G21F 9/16 C02F 11/00 B01J 20/00

Claims (3)

(57) [Claims] (1) There is a work clothes worn by a worker in a nuclear facility.
Or radioactive laundry wastewater generated after washing
Alternatively, the concentrated waste liquid is mixed with a water-absorbing material that is flammable and does not generate harmful substances when burned, and is stirred.The water-absorbing material absorbs the water in the radioactive waste liquid to convert the radioactive waste liquid into a solidified substance . A method for treating a radioactive waste liquid, comprising incinerating the converted product . 2. A have your <br/> the method for treating a radioactive liquid waste according to claim 1, wherein the moisture absorbing material, acrylic acid-vinyl alcohol copolymer, acrylic acid polymers, in pump do the acrylate A method for treating a radioactive waste liquid, comprising using a polymer water absorber of a starch-based polymer obtained by graft-polymerization of styrene or the like, or a cellulose-based polymer obtained by graft-polymerizing an acrylate or the like to carboxyl cellulose or the like. 3. Working clothes worn by workers in a nuclear facility
Or radioactive laundry wastewater generated after washing
Or the concentrated waste liquid is converted to polyethylene oxide
Mix with body and release to modified polyethylene oxide
Radioactive waste liquid by absorbing water in radioactive waste liquid
Is converted to a solidified product and incineration of the converted product is
A method for treating radioactive waste liquid .