Method of removing radioactive contaminations

Purpose: To conduct the decontaminating operation for radioactive contamination by distinctly indicating the contaminated range visually and while judging the residual range of the radioactive contamination visually. Method: Pigments are coated over a range where radioactive contaminations are detected and, after pigmenting the contaminated range, decontaminations are repeated by a wet decontaminating process till the pigments are reduced to a predetermined amount thereby eliminating the radioactive materials. The pigments within the grain size ranging from 1 to 10 μm is adequate, since this is substantially the same as the grain size of the radioactive cruds from nuclear power plant and exhibits the similar physical behaviors. Further, when an organic pigment is used in admixture with water, the pigments are not secured to the coating surface but can removed by waste cloth wiping easily. Thus, the radioactivity can be eliminated to a detectable limit by merely taking notice of the residual amount of the pigments thereby making it possible to improve the working efficiency, decrease the radiation dose and save the inspection frequency. (Kamimura, M.)