Pressure suppression containment system

A pressure suppression containment system 14 includes a containment vessel 24 surrounding a reactor pressure vessel 16 and defining a drywell 26 therein containing a non-condensable gas. An enclosed wetwell pool 28 is disposed inside the containment vessel 24, and a gravity driven cooling system (GDCS) pool 44 is disposed above the wetwell pool 28 in the containment vessel 24. The wetwell pool 28 includes a plenum 32 for receiving the non-condensable gas carried with steam from the drywell 26 following a loss-of-coolant-accident (LOCA). The wetwell plenum 32 is vented to a plenum 47 above the GDCS pool 44 following the LOCA for suppressing pressure rise within the containment vessel 24. A method of operation includes channeling steam released into the drywell 26 following the LOCA into the wetwell pool 28 for cooling along with the non-condensable gas carried therewith. The GDCS pool 44 is then drained by gravity, and the wetwell plenum 32 is vented into the GDCS plenum 47 for channeling the non-condensable gas thereto.