Transactions of the Korean Nuclear Society Virtual Autumn Meeting December 17-18 Evaluation for Accident Mitigation Effect of External Injection at WH600 using MELCOR

After the Fukushima nuclear power plant accident, the lesson was learned for the risk of the beyond design basis external event (BDBEE). In most existing accident management systems, if the engineering safety system becomes unavailable due to the BDBEE, there were no separate facilities and procedures and the accident could progress to a severe accident [1]. Hence, a multi-barrier accident coping strategy (MACST) was established to prevent that BDBEE proceeds into a severe accident. The MACST consists of three phases: using the facilities installed in the plant initially, using the MACST equipment, and using the off-site facilities with the MACST equipment in the long term [1]. The MACST includes mobile equipment such as power generation vehicles, external injection pumps, heat exchangers, etc. [2]. Besides, existing guidelines are being improved and MACST operating guideline is being developed [3]. The effectiveness of accident mitigation strategies may differ depending on the action taken by the operator and the strategies for MACST equipment have not been systematically established. Hence, it is necessary to evaluate the mitigation effect according to the procedure of strategy. Therefore, in this study, accident mitigation performance is evaluated for the external injection pumps. 2. Methods