Effects of Multiple Pipes Break Accident in SMART-P Using RELAP5/SMR Code

SMART-P (System integrated Modular Advanced ReacTor) is an integral reactor being developed with indigenous technology and has many key design features that are highly unconventional in comparison to the commercially operating reactors. Such design features include self-pressurizing pressurizer, helically coiled once through steam generators, PRHRS (Passive Residual Heat Removal System), power operation under natural circulation, and twisted fuel rods of roughly square cross section. In SMART-P SAR (Safety Analysis Report), the SBLOCA (Small Break Loss Of Coolant Accident) analysis is restricted to only single pipe break. However, if there are some break accidents at an annular cap or a center cap, multiple pipes break accident is likely to happen in reality due to the dynamic effect from the broken pipe. Accordingly, in licensing review process, thermal-hydraulic behavior of multiple pipes break accident is requested in addition to that of single pipe break accidents such as SI pipe break accident and pressurizer-gas cylinder connection pipe break accident. The objective of this study is to analyze thermal hydraulic response for multiple pipes break to support the licensing review in KINS. And the calculation results of multiple pipes break accidents were compared with those of various small break LOCAs to investigate the effects of multiple pipes break