線照射下希釈海水中における原子炉容器用鋼の腐食試験,1; 50Cでのヒドラジン添加の影響

Corrosion tests of vessel steels in diluted seawater under rays irradiation, 1; Effects of hydrazine addition at 50C

中野 純一; 塚田 隆 

Nakano, Junichi; Tsukada, Takashi

東京電力福島第一原子力発電所では、海水が炉心に注入された。炉心損傷により格納容器内が極めて高い放射線量となった。このため、格納容器及び圧力容器鋼の腐食が水の放射線分解により生じる酸素,過酸化水素などにより加速されることが懸念される。水の放射線分解が腐食に及ぼす影響と腐食抑制対策を探索するため、希釈人工海水中、50Cでの腐食試験を線照射下で行った。4.4kGy/h及び0.2kGy/hの線量率、及び非照射下での腐食試験を行った。ヒドラジンを10mg/L及び100mg/Lを添加し、線照射下での腐食に及ぼす影響を評価した。NH無添加の場合、0.2kGy/hと非照射下での腐食減量はほぼ同等であり、4.4kGy/hでの腐食減量は非照射下での1.7倍程度であった。

The seawater was injected into the reactor cores in the Fukushima Daiichi Nuclear Power Plant. Dose in primary containment vessels increased due to the core damage. Under high dose situations, oxygen, hydrogen peroxide, etc. are produced by water radiolysis. It is considered that effects of corrosion on steels would be assisted. To investigate effects of water radiolysis on corrosion of steels and countermeasure for the degradation of the steel components, corrosion tests in diluted artificial seawater at 50C were performed under rays irradiation and unirradiation. Flasks for corrosion tests were located on the positions of 4.4 kGy/h and 0.2 kGy/h. Hydrazine (NH) of 10 mg/L and 100 mg/L were added to the flasks. In situation without NH, weight loss of specimens irradiated with 0.2 kGy/h was equivalent to that of unirradiated specimens. Weight loss of specimens irradiated with 4.4 kGy/h was about 1.7 times that of unirradiated specimens.