An alternative cooling solution during loss of coolant accident with emergency core cooling system failure in NUSCALE nuclear reactor

Emergency action by operator is required when an accident goes together with safety system failure. This study aims to discover an alternative way out for the event of loss of coolant accident (LOCA) that is followed by the emergency core cooling system (ECCS) failure in the NUSCALE reactor. Procedure being investigated is to use the steam generator (SG) as a means to remove heat in the primary system. Heat removal by the SG is modelled and solved numerically. The heat load of steam and the core's decay heat during the ECCS failure are determined based on open literatures. In addition, RELAP5 calculation is used for benchmarking the results. From the reactor condition analysis, it is revealed that the golden time is about 10.2 h. In optimizing water supply, a two-step cooling strategy is suggested. The first step is to quickly condense the steam so that the primary system pressure is reduced. This requires water flow injection of 6218.3 kg/s. Subsequent step is to maintain pressure and temperature remains low by removing the decay heat, which need about 8.0 kg/s. Discussion shows that the pressure of primary system can be brought low so that the steam leakage is ceased. This indicates that simple calculation is applicable for evaluating accident management measures during LOCA.