Integrated thermal-hydraulic analysis using GOTHIC code during SBO for maanshan plant

This study employs the GOTHIC 8.2 code to simultaneously calculate the thermal-hydraulic behavior of the Nuclear Steam Supply System (NSSS) and containment of Maanshan 3-loop PWR Plant during the Station Blackout (SBO) event. The NSSS and the containment are modeled in a single GOTHIC model. The important features related to the SBO are considered in the model, such as reactor coolant pump (RCP) seal leakage, steam generator depressurization, and steam generator water makeup using a turbine-driven auxiliary feedwater system (TDAFWS). The RCP seal leakage flow depends on the pressure difference between reactor coolant system (RCS) and containment. Also, there is a sensible heat transfer between the RCS and containment. Thus, the NSSS and containment response are interactively calculated in a single code. This is different from the approaches which perform the analysis using two separate computer codes. The simulation results from two distinct SBO cases reveal critical insight into the effect of secondary depressurization and the availability of the TDAFWS. For the case with TDAFWS available but no manual depressurization for secondary system, the reactor will become uncovered within 8 h. The containment pressure and temperature will increase but remain below the respective design values. For the case with manual depressurization but no TDAFWS available, the RCS pressure will drop to the accumulator actuation setpoint, but accumulator is assumed unavailable in this analysis. The reactor core will become uncovered eventually. This study demonstrates that the thermal-hydraulic response for both NSSS and containment during SBO can be determined using a single GOTHIC code.