JPS58157999A - Electrolytic polishing and decontaminating device - Google Patents

Abstract

PURPOSE:To prevent the generation of electrolyte mists in the stage of decontaminating the metallic parts contaminated with radioactive materials by electrolytic polishing by providing an air permeable defoaming layer consisting of a specific material on the surface of the electrolyte in an electrolytic cell. CONSTITUTION:Metallic parts 3 contaminated with radioactive materials are immersed in the electrolyte 2 in an electrolytic cell 1, and voltage is impressed between said parts and an electrode 5 to remove the contaminating materials on the surfaces of the parts 3 by electrolytic polishing. Electrolyte mists are generated by the gases consisting essentially of oxygen and hydrogen generated from both electrodes 3, 5 in this stage, and scatter from the surface of the electrolyte to pollute the working environment and to corrode the device. In order to prevent the generation of such mists, an air permeable defoaming layer 7 constituted of wire-net-like or floatable granular materials made of a material having high corrosion resistance such as ''Teflon '', PVC, PE or the like is placed on the surface of the electrolyte 2. The generation of the electrolyte mists is suppressed by the layer 7.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to an electrolytic polishing device for electrolytically polishing piping, equipment, etc. of nuclear power generation equipment, and in particular to suppressing the generation of mist due to bubbles generated during electrolytic polishing. The present invention relates to an electrolytic polishing device equipped with a mechanism. - [Technical background of the invention and its problems] At a nuclear power plant, it is necessary to remove surface contamination from radioactive materials from equipment used to reduce the air dose rate inside the reactor building.

In particular, during safety inspections, workers often work close to various reactor equipment installed in the reactor building, so it is important to remove surface contamination from the reactor equipment in advance.

On the other hand, it is important to remove surface contamination from radioactive materials and reduce the radioactivity level of metal waste, etc. whose surface has been contaminated by radioactive materials, in order to carry out subsequent handling and processing operations.

Currently, the amount of radioactive metal waste whose surface has been contaminated by radioactive materials is gradually increasing.

However, surface decontamination techniques can be very effective in reducing the amount of radioactive waste if the surface contaminants are completely removed, allowing treatment similar to general metal waste. It is.

Electrolytic polishing has begun to be used to remove surface contamination because it is capable of removing radioactive substances that have entered the interior of metal crystal structures, and it is easy to control the amount of polishing.

This technology is expected to contribute to the reduction of radioactive metal waste when nuclear reactors are decommissioned in the future.

By the way, when electrolytically polishing nuclear reactor piping, various nuclear reactor equipment, tools, etc. that are contaminated with radioactive substances, a mist of electrolyte is generated by the gas generated from both electrodes.

The gases generated are mainly oxygen and hydrogen, so ventilation is necessary to avoid the risk of explosion.

At this time, the electrolyte mist containing radioactive substances is carried along with the gas, so it is necessary to remove the mist or suppress its generation in order to protect against air pollution and prevent deterioration of the ventilation system due to the electrolyte.

[Purpose of the invention]

The present invention has been made based on the above circumstances, and its purpose is to provide an electrolytic polishing decontamination device that suppresses or removes the electrolyte mist generated when electrolytically polishing metal objects contaminated with radioactive substances. It is to be.

[Summary of the invention]

That is, the present invention includes an electrolytic cell storing an electrolytic solution, an electrolyte contaminated with radioactive substances and an electrode immersed in the electrolytic solution, and a power source that applies a voltage between the electrolyte and the electrode. In the electrolytic polishing decontamination apparatus equipped with the above, an air-permeable defoaming layer made of at least one of Teflon (tetrafluoroethylene copolymer), polyvinyl chloride, polyethylene, and vopropylene is provided on the upper surface of the electrolyte. This is an electrolytic polishing decontamination device featuring:

[Embodiments of the invention]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an electrolytic polishing decontamination apparatus according to the present invention will be described below with reference to FIG. 1 and the accompanying drawings.

In FIG. 1, an electrolytic solution 2 is stored in an electrolytic cell 1, and an object 3 to be decontaminated is immersed in the electrolytic solution 2. As shown in FIG.

The object to be decontaminated 3 to which the conductor 4 is connected and the electrode 5 immersed in the electrolyte 2 are each connected to a power source 6.
voltage is applied between the object to be decontaminated 6 and the electrode 5.

A breathable defoaming layer 7 is provided on the upper surface of the electrolyte 2 of the device.

The object 6 to be decontaminated is miscellaneous solid waste.

As the defoaming layer 7, a multi-layer mesh wire mesh 7a shown in FIG. 2 i1) and -) or a floating granular material 7b shown in FIG. 3 is used.

In addition, (a) in FIG. 2 is a top view, and (a) is a cross-sectional view.

Examples of the materials forming the defoaming layer 7 include Teflon (tetrafluoroethylene polymer), polyvinyl chloride,
At least one type of material having corrosion resistance and heat resistance, such as polyethylene and PP propylene, is used.

〔Effect of the invention〕

In this electrolytic polishing decontamination apparatus, when decontamination was performed using iron piping as the object to be decontaminated 3, as shown in FIG. Surface contamination decreased and became below pack ground level B.

The total amount of mist generated at this time was as shown in Figure 5, and it was found that the case where the antifoaming layer 7 was provided (indicated by the broken line d) was significantly reduced compared to the case where it was not provided (indicated by the line C). .

This eliminates the need to install a mist separator or the like, or even if a mist separator is installed, the service life is significantly extended.

An electrolytic polishing decontamination device provided with an antifoaming layer in this manner has great effects, such as ease of maintenance of the device and a significantly extended lifespan.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view showing a partial block diagram of an embodiment of the device according to the present invention, and FIGS. 2 and 3 are top views showing a specific example of the defoaming layer used in the device shown in FIG. 4 is a diagram showing the relationship between the polishing time and the amount of surface contamination in the device shown in FIG. 1. FIG. 5 is a diagram showing the relationship between the polishing time and the total amount of mist generated in the device shown in FIG. 1. . 1... Electrolytic cell 2... Electrolyte 3... Electrolyte 4... Conductor wire 5... Electrode 6...・Power supply 7 ..... Patent attorney representing anti-foaming layer Sasu Suyama - Figure 1 (α) (b) A large number of dangerous structures

Claims (1)

[Claims] 1. An electrolytic cell storing an electrolytic solution, an electrolyte contaminated with a radioactive substance immersed in the electrolytic solution and an electrode, and a voltage applied between the electrolyte and the electrode. In an electrolytic polishing decontamination device equipped with a power source, Teflon (tetrafluoroethylene polymer), vinyl chloride,
An electrolytic polishing decontamination device characterized by having an air-permeable defoaming layer made of at least one of polyethylene and polypropylene. 2. The electrolytic polishing decontamination device according to claim 1, wherein the antifoaming layer is made of a multilayer mesh or a spongy body. 3. The electrolytic polishing decontamination apparatus according to claim 1, wherein the antifoaming layer is made of floating granular material.