原子炉容器鋼の腐食抑制対策に向けた線照射下での腐食試験

Corrosion tests under rays irradiation to examine measures for corrosion inhibition of reactor vessel steels

中野 純一; 山本 正弘 ; 塚田 隆 ; 山縣 諒平

Nakano, Junichi; Yamamoto, Masahiro; Tsukada, Takashi; Yamagata, Ryohei

東京電力福島第一原子力発電所では、炉心冷却の緊急措置として海水の注入が行われた。燃料デブリおよび核分裂生成物により、原子炉格納容器内は高い放射線量となっている。水の放射線分解生成物により格納容器鋼および圧力容器鋼の腐食が加速することが懸念されている。線照射下の希釈人工海水中での鋼材の腐食試験を行った。非照射と線量率0.2kGy/h以下では腐食減量が同程度だが、線量率0.6kGy/h以上では非照射よりも腐食減量が増加した。照射下において、大気雰囲気よりもN雰囲気において腐食減量が低下した。また、大気雰囲気でのNH添加は効果がないが、N雰囲気でのNH添加は腐食減量の低下に有効であった。

In the Fukushima Daiichi Nuclear Power Station, seawater was injected into the reactor cores as an emergency measure for the core cooling. Radiation dose is high in the primary containment vessels (PCVs) because of the fuel debris and the fission products. It is considered that corrosion of the PCVs and the reactor pressure vessels is accelerated by the products of water radiolysis. Corrosion tests were conducted in diluted seawater at under -rays irradiation. Weight loss in the diluted seawater irradiated with dose rates 0.2 kGy/h was comparable with that without irradiation. Weight loss in the diluted seawater irradiated with dose rates 0.6 kGy/h was higher than that without irradiation. Under irradiation, weight loss in N atmosphere was lower than that in air atmosphere. To reduce weight loss, hydrazine (NH) addition in air atmosphere was not effective while NH addition in N atmosphere was effective.