G101 Synopsis of the Accident at Fukushima Daiichi Nuclear Power Station caused by Earthquake and Tsunami

Fukushima Daiichi Nuclear Power Station lost all off-site power sources immediately after the earthquake which occurred at 14:46 on March 11, 2011.But the important safety features were retained for their safety functions with back-up power supply even after the earthquake. However the eventual flooding of the site caused by tsunami resulted in loss of all power sources, which led to the failure of cooling the reactor cores. As ad hoc measures such as alternative water injection using fire engines and primary containment vessel venting by assembling temporary equipment and manual operation were attempted. But core damage could not be prevented and hydrogen explosion occurred. Based on the identified lessons learned of the causes and issues that could not stop the accident, action plans are developed and are presented in this paper.