Chemical decontamination method and chemical decontamination apparatus

Abstract

Provided is a chemical decontamination method that shortens the decomposition time of a reduction decontamination agent. An oxidization decontamination, a decomposition of an oxidization decontamination agent, and reduction decontamination using an oxalic acid aqueous solution are performed on a target piping of a BWR plant. After that, the oxalic acid is decomposed (S). That is, a part of the oxalic acid is decomposed by irradiating the oxalic acid aqueous solution with ultraviolet rays upstream of a decomposition device (S), and Fein the aqueous solution is converted to Fe. Hydrogen peroxide is supplied to the decomposition device (S). In the decomposition device, the oxalic acid is decomposed by a catalyst and hydrogen peroxide, Feand hydrogen peroxide react to produce Feand OH*, and the oxalic acid is decomposed by OH*. A corrosion potential of the aqueous solution flowing out from the decomposition device is measured (S). A concentration ratio calculation device obtains Fe/Fe(concentration ratio) based on the corrosion potential (S), and A control device controls the supply amount of hydrogen peroxide to the decomposition device based on Fe/Fe(Sand S).).