Passive Containment Cooling System (PCCS) response with Drywell Gas Recirculation System (DGRS) activated during a severe accident scenario with release of non-condensable gas

The paper presents the experimental results of an integral containment test named T2.1 performed in the PANDA facility. Test T2.1 investigated the effect of a Drywell Gas Recirculation System (DGRS) activation on a Passive Containment Cooling System (PCCS), during a postulated severe accident with release of hydrogen later during the transient (in PANDA facility Helium is used to simulate hydrogen). The containment initial thermal-hydraulic conditions (e.g. temperature, pressure, gas composition, decay heat, etc.) in test T2.1 represent the situation predicted at 1 h after a Loss of Coolant Accident (LOCA) for a specific ESBWR design. Test T2.1 simulated the decay heat which would be released during a transient of about 12.5 h, including structural heat release in the early phase. Test T2.1 includes four main phases. The first phase, lasting for about 10,000 s simulated a LOCA 1 h after SCRAM. The second phase, helium was injected for about 7200 s and the DGRS was activated. The third phase was carried on from 17,200 s to about 43,200 s by keeping the DGRS in operation. In the fourth phase the DGRS was switched off and was observed the PCCS response.

► Passive condensers stabilize system pressure also in the presence of non-condensable light gas.
► The DGRS operation in PANDA test T2.1 mitigates the system pressure build-up.
► Non-condensable gas retention in the drywell with DGRS mitigates system pressure.