Abstract
The Fukushima Daiichi Nuclear Plant, Unit No.1, 2 and 3 which were under operation were automatically shut down when the earthquake occurred. After the earthquake, the tsunami reached the planst and all AC power was lost. This loss of AC power made it impossible to supply cooling water into the pressure vessel. After that, the water level in the pressure vessel became less and the meltdown occurred. But the loss of coolant and core uncovery process is unclear, because the plant parameters (water level, pressure, etc) could not be checked in the situation of loss of electric power. Now we are performing the numerical evaluation regarding to the core uncovery process in the Fukushima Daiichi Nuclear Plant Unit No.1 accident with the TRAC-BF1 code. In this study, the core uncovery process and the effect of isolation condenser for the reactor core cooling were investigated. This paper describes the results of the numerical evaluation on the core uncovery process.
