Lessons Learned from the Process Focusing on Achieving the State of Cold Shutdown of Fukushima Daiichi Nuclear Power Plant Accident

Abstract

Fukushima Daiichi Nuclear Power Plant caused a severe accident which released a large amount of radioactivity triggered by the Great East Japan Earthquake. The existing investigation reports of the accident prepared by several institutions pay attention only to the process which caused the accident but not much to the accident mitigation or the recovery process. This study focused on Unit 3 of Fukushima Daiichi Nuclear Power Plant, including its recovery process from the accident. Based on the public data, the time sequences for the recovery process between the accident occurrence and the state of cold shutdown were classified. Then, the groups of actions were sorted out in terms of ergonomics viewpoint. The important responses in the recovery process were identified and analyzed referring to the m-SHEL model. As a result, new lessons were learned from the accident case regarding the actions required for recovering from the accident. 東京電力㈱福島第一原子力発電所は，東日本大震災による電源喪失等によって，放射性物質を大量に放出 する過酷事故に至ったが，その後冷温停止状態を達成した．しかし，福島第一原子力発電所事故に関するさ まざまな機関による調査報告書は，事故に至った過程に着目している一方で，事故の拡大の防止や被害の減 少についてはほとんど着目していない．本研究は，福島第一原子力発電所の3号機における，冷温停止状態達 成までの過程に着目した．公開データに基づき，事故の発生から冷温停止状態達成に至るまでの時列を整理し， それらを人間工学的視点によって行為群を分類した上で，状況の回復に重要な意味をもつ対処をm-SHELモ デルを援用して分析した．このようなアプローチにより，状況の回復に必要な行為に関する新たな教訓を得た． (キーワード：福島第一原子力発電所事故，3号機，事故調査，回復，高濃度汚染水，循環注水冷却，冷温 停止状態，人間工学，社会技術システム，m-SHELモデル)