ガンマ線照射下におけるヒドラジン添加希釈海水中での炭素鋼および低合金鋼の腐食

摘要

Seawater was injected into reactor cores of Units 1,2, and 3 in the Fukushima Daiichi nuclear power station as an urgent coolant. It is considered that the injected seawater causes corrosion of steels of the reactor pressure vessel and primary containment vessel. To investigate the effects of gamma-rays irradiation on weight loss in carbon steel and low-alloy steel, corrosion tests were performed in diluted seawater at 50℃ under gamma-rays irradiation. Specimens were irradiated with dose rates of 4.4 kGy/h and 0.2 kGy/h. To evaluate the effects of hydrazine (N_2H_4) on the reduction of oxygen and hydrogen peroxide, N2H4 was added to the diluted seawater. In the diluted seawater without N_2H_4, weight loss in the steels irradiated with 0.2 kGy/h was similar to that in the unirradiated steels, and weight loss in the steels irradiated with 4.4 kGy/h increased to approximate 1.7 times of those in the unirradiated steels. Weight loss in the steels irradiated in the diluted seawater containing N_2H_4 was similar to that in the diluted seawater without N_2H_4. When N_2 was introduced into the gas phase in the flasks during gamma-rays irradiation, weight loss in the steels decreased.%ガンマ線照射下，50℃において200倍希釈人工海水中腐食試験を実施し，炭素鋼および低合金鋼の腐食に及ぼすガンマ線照射の影響およびN_2H_4添加が及ぼす放射線分解水質に対する影響を検討した。N_2H_4添加に加え，気相部をN_2雰囲気にした腐食試験も実施した。その結果，以下のことが明らかになった。