Method of decontaminating reactor components in a nuclear facility

Purpose: To provide a method of chemical decontamination by reducing corrosions and improving the decontamination effect in structural materials. Method: Surface of structural materials or equipments of a nuclear reactor to be decontaminated is, at first, exposed to an aqueous alkali solution containing 1 - 15 % by weight of potassium permanganate as a first solution at 70 - 900C for 1 - 6 hours and then well-washed with water, in which insoluble Cr+3 as a constituent element of spinel oxides formed on the surface of stainless steels is oxidized into insoluble Cr+6 and dissolved. Then, the surface is exposed to an aqueous solution containing 2 - 6 % by weight of citric acid, an amine or ammonium salt thereof and 1 - 3 % by weight of oxalic acid, amine or an ammonium salt thereof as a second solution at 50 - 800C for 0.5 - 1.5 hours, followed by water washing. Thus, the spinel oxides dissolved or rendered easily soluble by the first solution are rapidly removed. (Kamimura, M.)