Patent Number: 053023242
Section: summary

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for the decontamination of a substance contaminated with radioactivity produced in a nuclear power station or the like, and to a method and an apparatus for the decontamination of a material used for said decontamination. 2. Description of the Prior Art Heretofore, in a nuclear power station, with the passage of time substances contaminated with radioactivity are produced due to contact of apparatus and the parts thereof with radioactivity. Such contaminated apparatus or parts are generated as replaced or disposed forms at the time when the apparatus are subjected to routine inspection or overhaul. Otherwise, there occurs no replacement of the part, however, some apparatus contaminated are generated to be necessarily coated. The degree of contamination of these contaminated substances can be out of the specified range according to safety standards. To dispose of these substances large size substances are cut into small size substances, contained in metal drums, and then they are usually confined in abandoned mines or the like, or kept or dumped in storage places which are constructed in regions with few inhabitants located apart from urban areas. In the present invention, said terms "keeping and dumping" are unified as one word "dumping" for convenience. The amount of substances contaminated with radioactivity stated above increases every year by the operation of nuclear power stations, resulting in lack of places to dump these substances. New waste-dumping places, therefore, become necessary. Then when a new waste-dumping place is selected, however, the inhabitants near the place tend to make an opposition movement leading to social problems. The present invention is intended to solve such troubles. The object of the invention is to provide a method and an apparatus for the decontamination of substances contaminated with radioactivity which comprises decontaminating substances contaminated with radioactivity as mentioned above, enabling the decontaminated substances to have less radioactivity than that required by safety standard, therefore, allowing the substances to be dealt with as general industrial wastes, and enabling the use of a greatly reduced area of waste-dumping place. Another object of the invention is to to provide a method and an apparatus for the decontamination of materials used for the decontamination of the substance mentioned above which comprise decontaminating fully said materials, regenerating the materials, and permitting the re-use thereof. BRIEF SUMMARY OF THE INVENTION The present invention is directed to provide a method for the decontamination of substance contaminated with radioactivity which comprises applying shotblast or sandblast to the substance to remove matters adhered to the surface of the substance, then cleaning the surface of the substance using liquid, washing the grit of said shotblast or sandblast with an organic solvent, filtering the organic solvent used for the washing, vaporizing the organic solvent comprising residue removed by heating, liquefying and recovering the vaporized solvent, and washing the washed grit with a solution containing a chelate compound. In addition, as far as the decontaminating apparatus of the present invention is concerned, it is an apparatus for the decontamination of the substance contaminated with radioactivity comprising means for shotblasting or sandblasting; means for washing the grit of the shotblast or sandblast with an organic solvent; means for filtering washing liquid used for the washing; means for purifying which comprises heating said filtered washing liquid, liquefying and purifying by cooling; and means for washing using a liquid containing chelate compound. Further, a method for decontaminating the material used for the decontamination mentioned above which comprises washing the grit of shotblast or sandblast, being applied to the substance contaminated with radioactivity, with an organic solvent, filtering the organic solvents used for the washing, vaporizing the filtered organic solvent by heating, liquefying and purifying the vaporized organic solvent by cooling, and washing said washed grit with a liquid containing chelate compound. Further, as for a decontaminating apparatus for the material used for the decontamination of the substance contaminated with radioactivity, the apparatus comprising means for filtration being made corresponding to a means for washing the grit of shotblast or sandblast; means for purifying organic solvent which comprises evaporizing the organic solvent by heating and liquefying the solvent by cooling; and means for washing a chelate liquid using a solution containing chelate compound. Further, a method of the decontamination of substances contaminated with radioactivity which comprises washing said substance by the use of a washing apparatus containing a liquid as well as having means for ultrasonic vibration. Further, an apparatus for the decontamination of substances contaminated with radioactivity comprising a vessel containing a liquid as well as having means for ultrasonic vibration.