A study of fukushima nuclear power plant accidents by the viewpoint of PSA

Abstract

On 11th March, 2011, most sever nuclear power plant accidents in the history have been occurred at the Fukushima site due to the massive earthquake and subsequent large Tsunami. As the results of the loss of all AC power or station blackout, the reactor cores have melted down in Unit 1 through Unit 3. In the present study, the core damage probabilities for Units 1 through 3 have been evaluated by event tree analyses under the condition of the loss of all AC power or station blackout. The core damage probability at 168 hours (7 days) after the Tsunami are obtained as 0.80(Unit 1), 0.40(Unit 1) and 0.30 (Unit 3). The discussions are made based on the discrepancy between the analysis results and the actual situation, that is, all the three reactor cores have melted down.