Uncertainty Analysis for Station Blackout Scenario

In the wake of Fukushima Dai-ichi NPP accident, the diverse and flexible coping strategies (FLEX) have been proposed for advanced nuclear reactors to enhance the coping capability of extended station blackout. In this work, the uncertainty analysis is performed to analyze a station blackout for APR1400 nuclear reactor by calculating the key parameters and quantifying the safety margin. APR1400 model was generated using MARS-KS thermal-hydraulic code. 16 uncertain parameters were identified and an uncertainty analysis framework was developed by coupling MARS-KS and Dakota statistical tool. Afterwards, a sensitivity analysis is conducted with core exit temperature and peak cladding temperature selected as safety parameters. For the sensitivity analysis, the accident was split into two phases: before and after the alignment of the FLEX equipment. The major contributors to a higher core exit temperature are: initial pressurizer pressure, initial secondary pressure, reactor power, SIT inventory and SIT temperature. A high safety margin is quantified which demonstrates the robustness of the emergency procedures which contemplates the use of FLEX equipment and TDAFWP to cope with 72 hours of station blackout.