Investigation of the RCS-containment integral effect test on intermediate and small break loss-of-coolant accident (LOCA) transients

Considering the importance of the pressure build-up depending on the mass / energy (M/E) release from a reactor coolant system (RCS), the ATLAS-CUBE integral effect test facility was utilized to simulate the thermal–hydraulic interaction between a RCS and a containment. To investigate the effect of the break size on the pressure / temperature (P/T) build-up in a containment, this study focused on the integral effect tests for an intermediate-break loss-of-coolant accident (IBLOCA) and a small-break loss-of-coolant accident (SBLOCA). As the test results, the decrease of the coolant water level in the RCS according to the cold leg break induced the core heat-up and the reactor core was cooled down after the safety injection to the RCS. The P/T transient of a containment could be highly dependent not only on the break size, but also on the two-phase flow characteristics and the initial temperature of the steam-gas mixture in a containment.