Design options for the safety injection system of Korean next generation reactor

Loss of coolant accident (LOCA) analyses for various con®gurations of safety injection system (SIS) are performed to optimize the emergency core cooling system (ECCS) perfor- mance for the Korean next generation reactor (KNGR). The KNGR is an advanced light water reactor (ALWR) adopting the advanced design feature of a direct vessel injection (DVI) con®guration and passive ¯uidic device in the discharge line of the safety injection tank (SIT). To determine the feasible SIS con®guration and the optimum capacities of the SIT and high pressure safety injection pump (HPSIP), licensing design basis and best estimate LOCA ana- lyses are performed for the limiting large break and small break spectrum, respectively. The analyses results show that the four-train DVI injection with the current system design is a more feasible con®guration than the other ones considered and the adoption of a ¯uidic device SIT enhances the ECCS performance for large break LOCA. For small break LOCA, in the case of cold leg break, the DVI4 con®guration is better than other con®gurations and also meets the EPRI ALWR requirement of no core uncovery for up to a 15.24 cm (6 in) diameter small break. However, in the case of DVI line break, slight core uncovery is pre- dicted and also the system behavior is signi®cantly a€ected by reactor vessel (RV) downcomer modeling. Therefore, the DVI4 con®guration is more feasible for KNGR ECCS performance, but further investigations are required to resolve the ECCS bypass issues for large break LOCA and to develop a proper RV downcomer model for analysis of DVI line break in small break LOCA