Electrolytic Decontamination of Surface-Contaminated Metal by Alternating Electrolysis Using Square-Wave Current in a Neutral Salt Electrolyte

Alternating square-wave current electrolysis using a Na₂SO₄ electrolyte was studied as a removal method for radioactive contaminated oxidation film on metal surfaces. After the oxidation film was selectively removed using the Na₂SO₄ electrolyte, base metal was removed. Based on a diffusion model in which the removal rate of the surface oxidation film depends on the diffusion rates of O^2- and Fe²⁺ ions in the film, the optimum cycle of the alternating square current was estimated to be 90 s (the square widths of the negative and positive currents were 60 and 30 s, respectively). The theoretical estimation was in good agreement with the experiment results. Using this decontamination method, decontamination factors of 10¹ to 10⁴ were obtained for stainless steels of a boiling water reactor coolant system and radioactive simulated samples.