Comprehensive safety assessments of MONJU taking into account the accident at Fukushima Dai-ichi Nuclear Power Station of Tokyo Electric Power Company

Fast Breeder Reactor Research and Development Center, Tsuruga Head Office

Comprehensive safety assessments of MONJU taking into account the accident at Fukushima Dai-ichi Nuclear Power Station of Tokyo Electric Power Company have been performed based on the request of Nuclear and Industrial Safety Agency on July 22, 2011. The assessments focus on earthquake and tsunami as natural phenomena as well as the loss of all alternating current power sources (SBO: Station Blackout) and loss of the ultimate heat sink (LUHS) as the loss of safety functions. Assessed systems are the reactor, the ex-vessel storage tank (EVST) and the spent fuel pool (SFP). The safety margins are assessed by evaluating the scale of events that the plant could withstand against the events beyond design basis without significant damage to the fuel. The ability of natural circulation in primary cooling systems and natural convection of air in the auxiliary air cooling system are taken into account in the assessment for the reactor and the EVST in SBO.