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概要

Noble metal chemical addition (NMCA) technology has been widely adopted for BWR plants in the US as a means to mitigate stress corrosion cracking (SCC). Dose rate of the reactor water recirculation system piping of some BWR plants that apply a combination of NMCA and zinc injection technology have gradually decreased. Chemical decontamination removes 60Co, but also the noble metal from the piping surfaces. Thus, effect of dose rate reduction by NMCA is decreased in the plant operating period after chemical decontamination. We considered that platinum deposition treatment just after chemical decontamination before plant operation would be effective to prevent redeposition of the 60Co. In this platinum deposition treatment process, Sodium hexahydroxyplatinate (IV), hydrazine and ammonia are used as the treatment chemicals. A 60Co deposition reduction effect of 1/2 compared to non-treatment is confirmed for up to 1,000 hours by laboratory experiments.

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