Fukushima Daiichi - A One Year Review

First of all, we deeply apologize to all residents of Fukushima Prefecture as well as broader society for the concern and anxiety that has arisen on account of the accident at Fukushima Daiichi Nuclear Power Station (NPS) due to the March 11, 2011 Tohoku - Pacific Ocean Earthquake.

The accident at Fukushima Daiichi NPS was caused by the loss of reactor core cooling functions and the prolonged simultaneous loss of all Alternate Current (AC) and Direct Current (DC) power due to the 13 meter-height tsunami brought about by the massive M9.0 earthquake.

What followed after was the extremely serious accident in which a series of explosions occurred at the reactor buildings and radioactive materials were released into the atmosphere and ocean.

Since then, we have been making a concerted effort to achieve a full recovery while receiving support from the government, relevant domestic and overseas organizations and manufacturers. As of December 2011, we have achieved conditions equivalent to a cold shutdown. This is the state where the inside reactor temperatures of Units 1 through 3 have decreased to approximately below 100 degrees C and the release of radioactive materials has been significantly suppressed and is being kept under control.

Currently, efforts to steadily cool down the reactors, control radioactive emissions into the atmosphere, and stop all radiation leakage into the ocean remain ongoing.

Hereafter, per the Mid-and-Long-term Plan prepared in conjunction with the government that was released in late December 2011, we will move forward with such activities including our primary mission to decommission Units 1 through 4.

In order to enable the evacuees to return home as soon as possible and restore peace of mind to all the citizens of Japan, we will do our best to maintain the cool state of the reactors and prevent further radioactive emissions.

In the following content, we will take a look back upon the tumultuous year that transpired at Fukushima Daiichi NPS and go over the many challenges we faced and how we dealt with them.

March, 2012


1. Accident Overview at Fukushima Daiichi NPS

The sequence of events leading to the loss of the reactor cooling function in the early stages of the accident

Implemented countermeasures to secure and continue reactor water injection

2. Present Status of Fukushima Daiichi NPS and Implemented Countermeasures

Achieved conditions equivalent to a cold shutdown in December, 2011.

Measures to control the release of radioactive materials into the atmosphere

Measures to prevent the outflow of radioactive materials into the ocean

Preventive measures against large earthquakes and tsunamis

Preventive measures against the outflow of contaminated water into the underground water Safety measures for workers

3. The Future Action Plans

3.1 Mid- and-long-term Plans

Current internal reactor status assessment and actions to be taken.

4. Conclusion

Appendix: Onsite Response Measures in the Early Stage of the Accident at Fukushima Daiichi NPS

Photo 1

Photo 1.Units 1-4 Reactor Building taken from the backside of the seismic isolated building
(photographed on January 9, 2012)