Thermal hydraulic phenomena related to small break LOCAs in AP1000

Since the TMI accident in 1979, a lot of attention in the nuclear engineering field has been drawn to the small break LOCA issue, around which plenty of work has been done both experimentally and theoretically. Subsequent reactor designs have also been greatly influenced. As a Generation III + reactor that received Final Design Approval by U.S. NRC, AP1000 employs a series of passive safety systems to improve its safety. However, the thermal hydraulic phenomena related to small break LOCAs in AP1000 have not been fully understood and further studies are still required. This paper investigated the available literature and information on thermal hydraulic phenomena that occur during small break LOCAs in AP1000, which included the critical flow, natural circulation, counter-current flow limiting, entrainment, reactor vessel level swell, direct contact condensation and thermal stratification. In particular, the physical phenomena, theoretical and experimental research conducted in the past few decades, and prediction models as well as their comparison and evaluation for the thermal hydraulic phenomena related to the small break LOCAs in AP1000 were concluded.