Abstract
The Fukushima Daiichi Nuclear Power Plant Unit 5 lost all AC power at 15:40 when tsunami struck triggered by the Great East Japan Earthquake on March 11, 2011. After a 9 day struggle, cold shutdown was achieved. This paper focuses on the processes of the Unit 5 recovery in consideration of important events that took place in the field. In particular, the actions of on site personnel who responded to the accident have been reviewed in light of resilience engineering concepts and guidelines. A hypothesis of time-flow structure of Responding, which is one of the four cornerstones of resilience engineering, was developed based on previous researches. This hypothesis was verified through an analysis of the path to cold shutdown of the Unit 5. Finally, the necessity for new safety concept of "Safety-II", which aims not only to reduce risks but also to expand successes, was pointed out and lessons learned from the Fukushima accident spotlighted on the Unit 5 how to overcome emergency difficulties were presented.
