Behavior and Response Capability of CANDU 6 NPP at Shutdown Condition during Extended Loss of All AC Power

After the Fukushima accident, there has been a growing interest in countermeasures against station black out (SBO) in nuclear power plants. In particular, there have been needs to prepare a strategy for responding to power plants considering the loss of all the AC power, so called the Extended Loss of All AC Power (ELAP). It would be seemed that the current Emergency Operating Procedures (EOP) of domestic nuclear industry is not enough to deal with the ELAP accident. So the additional procedures or strategies for coping with ELAP situation have been required. The purpose of this study is to identify the behavior and response capacity of the CANDU 6 plant (Wolsong Unit 1,2,3,4) during shutdown operation for ELAP. In case of analysis for the full power condition, the fuel cladding and pressure tubes are damaged within 2 hours without the operator actions during ELAP. The analysis was performed to estimate the behavior and the response of CANDU 6 plant at shutdown operation mode 4 with ECCS blocked during ELAP accident. If there is no operator action in the accident, the damage of the pressure tube occurs within about 7 hours.