Current situation of decommissioning work in Fukushima Daiichi Nuclear Power Station

A very large earthquake of magnitude 9.0 caused huge tsunami along the Pacific coast of Japan on 11th March, 2011. The earthquake is the fourth largest ever recorded worldwide. Simultaneous move of several regions along the Japan Sea Trench with area of 500 km x 200 km caused massive tsunami. The tsunami significantly exceeded stations design bases to cause station blackout. Emergency diesels and even DC batteries were lost, and it caused core melt-down to release large amount of radio activities. Now damaged cores are stable and cooled by circulating water. Roadmap for decommissioning work has been set, and work is now in progress. Through the accident, numerous lessons were learned. Already many countermeasures have been implemented in existing nuclear power stations for higher safety. To be prepared for the unpredicted in more flexible way to give higher resilience even in case of beyond design basis is the key point to be prepared against large natural disaster including huge tsunamis. (author)