Durability evaluation of steels for reactor pressure vessel/primary containment vessel

Nakano, Junichi; Tsukada, Takashi; Yamagata, Ryohei

The seawater was injected into the reactor cores in the Fukushima Daiichi Nuclear Power Plant. Dose in primary containment vessels (PCV) increased since the fuel debris fallen from Reactor Pressure Vessels (RPV) and fission products emitted radiation. Since oxygen, hydrogen peroxide, radicals etc. are produced by water radiolysis, it is considered that corrosion on the PCV and RPV steels would be caused. Corrosion tests in diluted artificial seawater at 50C were performed under rays dose rate of 4.4 kGy/h and 0.2 kGy/h, and unirradiation. Hydrazine (NH) of 10 mg/L and 100 mg/L were added to the flasks to evaluate the effects of NH on corrosion under rays irradiation. In situation without NH, weight losses of the specimens irradiated with 0.2 kGy/h were similar to those of the unirradiated specimens. Weight losses of the specimens irradiated with 4.4 kGy/h were approximate 1.7 times those of the unirradiated specimens.