RELAP5/MOD3.2 sensitivity analysis using OECD/NEA ROSA-2 project 17% cold leg intermediate-break LOCA test data

Takeda, Takeshi ; Watanabe, Tadashi; Maruyama, Yu ; Nakamura, Hideo  

An experiment simulating a PWR cold leg IBLOCA with 17% break at cold leg was conducted. The post-test analysis by RELAP5/MOD3.2.1.2 code revealed that cladding surface temperature was underpredicted due to later major core uncovery. The post-test analysis conditions were considered as Base Case assuming the discrepancies were caused by uncertainties in the code predictability and input data. Key phenomena and related important parameters, which may affect the cladding surface temperature, were selected based on the LSTF test data analysis and post-test analysis results. Sensitivity analyses were performed by changing the parameters relevant to the key phenomena within the ranges to investigate influences of the parameters onto the cladding surface temperature. It was confirmed that both constant C of Wallis CCFL correlation at the core exit and inter-phase drag in the core are more sensitive to the cladding surface temperature.