SBLOCA long term cooling procedure for the integral type PWR

An advanced integral-type pressurized water reactor (IPWR) with a maximum thermal power of 65 MW has been developed at the Korea Atomic Energy Research Institute (KAERI). This 65 MW IPWR enhances the safety and reliability by adopting inherent safety design characteristics and an advanced passive design feature. To identify the transient behavior and coolant distribution in the reactor coolant system (RCS) during a small break loss of coolant accident (SBLOCA), the break size spectrum analyses for the limiting break location are performed using a best-estimate code of MARS/SMR. The analysis results show that the safety systems of the 65 MW IPWR design adequately remove the core decay heat without causing a core uncovery for all the break cases. However, for some of the relatively large sizes of the breaks, the upstream region of the shutdown cooling system (SCS) suction pipe is completely voided after the break and it is not refilled with safety injection water throughout the transient, which prevents a proper operation of the normal SCS. Based on the results of this analysis, the 65 MW IPWR specific long term cooling (LTC) procedure, independent of a break size, is suggested instead of using the normal operation of the SCS.