Experimental investigation on thermal hydraulic interaction of RCS (reactor coolant system) and containment for intermediate break loss-of-coolant accident (IBLOCA) scenario in ATLAS-CUBE test facility

In order to experimentally investigate the thermal hydraulic interaction between the reactor coolant system (RCS) and the containment, the integral effect tests were conducted in a test facility, ATLAS-CUBE. Three tests for an intermediate-break loss-of-coolant accident (IBLOCA) were conducted for simulating the break of a cold leg or a direct vessel injection (DVI) nozzle. The effect of the mass/energy (M/E) supply from the break and the asymmetric phenomena inside the containment according to the break simulation position were investigated with considering its impact on the pressure/temperature (P/T) behavior inside the containment. As the test results, both of the RCS and the containment were effectively cooled down during the transient, by activation of the safety injection system and the containment spray system, respectively. The M/E supply from the RCS increased a pressure and a steam-gas mixture temperature of the containment, while a wall condensation on the passive heat sink and a spray injection contributed to cool down the steam-gas mixture. The two-phase flow characteristics of the break flow such as the quality or the subcooling of the liquid phase could highly affect the P/T build-up of the steam-gas mixture in the containment. The ATLAS-CUBE test data in this study will contribute to evaluate the thermal hydraulic safety analysis codes for the RCS and the containment.