| 摘要 |
PROBLEM TO BE SOLVED: To efficiently remove precipitated iron oxalate by decomposing a decontaminant to remove radioactive nuclides after decontaminating a region with a reductive decontaminant containing oxalic acid and adding an oxidant to a decontamination liquid to form an oxide film on the surface of a member. SOLUTION: Oxalic acid and hydrazine are poured from a chemicals tank 8 and a pH controlling tank 10 respectively into a region 1 to be decontaminated (hereinafter referred to as the region 1) by circularly passing water in the region 1 through the manipulation of a valve. With peroxide poured into a catalyst decomposition tower 6, subsequently, the passage of water through a cation resin tower 7 begins. After the concentration of the oxalic acid in a line becomes constant, decontamination is carried out by continuously pouring only hydrazine. Then, after reducing the quantity of poured peroxide and confirming that the concentration of oxalic acid and hydrazine respectively reaches a prescribed value, water is passed through a mixture floor resin tower 14 to clean the line with the water. Next, potassium permanganate is poured from a chemicals tank to decontaminate the region 1 by oxidation. Then, oxalic acid is poured to decompose ions of permanganic acid. Afterward, the same processes are repeated to clean the region until the electric conductivity of the water in the line becomes 1μs/cm or less.
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