Assessment on Recirculation Sump Performance for Pressurized Water Reactor Equipped with Incontainment Refueling Water Storage Tank

In 2003 USNRC (United State Nuclear Regulatory Committee) revised Regulation Guide 1.82 (RG. 1.82) to revision 3, and in 2004 issued generic Letter 2004-02 for PWRs (Pressurized Water Reactors). According to these regulatory actions sump blockage issue again has been placed on important safety problem. As a response of these USNRC's activities, NEI 04-07 was developed in order to evaluate the postaccident performance of a plant's recirculation sump, and has been used as a standard methodology. The baseline methodology of NEI 04-07 is composed of break selection, debris generation, latent debris, debris transport, and head loss. And the debris transport is evaluated using debris transport chart which is composed of blowdown transport, washdown transport, pool fillup transport, and recirculation transport. Such a debris transport chart was found suitable to PWR which is equipped with RWST (Refueling Water Storage Tank) outside the containment, and it was proposed that some improvement be required in order to apply to PWR which has IRWST (Incontainment Refueling Water Storage Tank). This paper discusses a full-scope evaluation method and gives evaluation results for APR1400 (Advanced Power Reactor 1400 MWe)