Evaluation of ECCS performance for an SBWR

A simplified boiling water reactor (SBWR), one of the next generation of light water reactors, is now under development. From the safety viewpoint, the SBWR is characterized by the adoption of a passive emergency core cooling system (ECCS) and a passive containment cooling system (PCCS). The ECCS network for an SBWR consists of depressurization valves (DPVs) and a gravity-driven cooling system (GDCS). The DPV and GDCS are designed to keep the core covered with water following any loss-of-coolant accident (LOCA) assuming a single failure in the ECCS. The SAPPHIRE code has been developed in order to evaluate the effectiveness of the ECCS of the SBWR. The SAPPHIRE code has been developed to calculate the short-term thermal-hydraulic phenomena simultaneously inside the contaminant including the RPV, drywell, and wetwell. The predictive capability of SAPPHIRE for SBWR LOCA analysis has been demonstrated by a comparison with the best estimate TRAC code. Both SAPPHIRE and TRAC codes indicate no core uncovery during a maximum drain line break