Integral Effect Test on Intermediate Break Loss-of-coolant Accident with Coupling RCS and Containment in ATLAS-CUBE Facility

Abstract

During an accident such as a loss-of-coolant accident (LOCA) or a steam line break (SLB), the released coolant from a reactor coolant system (RCS) increases a pressure and temperature (P/T) inside a containment, which is a crucial parameter to threaten an integrity of the containment wall and the equipment qualification (EQ). The ATLAS-CUBE integral effect test facility has been constructed to experimentally investigate the thermal hydraulic interaction between the RCS and the containment. This study focused on the C1.2 test in the OECD/NEA ATLAS phase 3 international joint project simulating an intermediate-break loss-of-coolant accident (IBLOCA) accident using the ATLAS-CUBE facility. The test result showed that the RCS was effectively cooled down during the transient by an activation of the safety injection system, which supplied the safety injection water to contribute the recovery of the coolant inventory in the reactor core. The mass and energy (M/E) supply from the RCS increased the pressure and the steam-gas mixture temperature of the containment, while the condensation of the steam on the passive heat sink wall contributed to cooling down the steam-gas mixture in the containment. The increasing rate of the containment pressure became smaller as the break flow changed to the two-phase flow with the subcooled liquid flow. The present integral effect test data can be used to evaluate the capability of thermal hydraulic safety analysis codes for the RCS and the containment, with considering the multi-dimensional or the multi-compartment models.