Abstract: An assembly includes a base grid configured to be disposed below a pressure vessel and spaced vertically above a floor of a containment vessel to define a sump therebetween. The assembly further includes an annular wall extending vertically upwards from the floor and laterally bounding the base grid and the sump. The wall separates the sump from a suppression pool, an inlet passage extending through the wall and providing flow communication between the sump and the suppression pool, and an outlet passage extending through the wall and providing flow communication between the sump and the suppression pool.

Abstract: Combination primary containment cooling system and residual heat removal steam condensers (PCCS-CND) operable in a containment cooling mode and in a reactor vessel cooling mode are described. In the containment cooling mode, the PCCS-CND interfaces with the primary containment vessel (PCV) through an isolation valve which can be normally closed or open. In the normally closed valve position, and upon receipt of a high drywell pressure signal, the valve opens allowing the steam in the PCV to flow to the PCCS-CND where it condenses, and the decay heat is transferred to the condenser pool. In the normally open valve position, the PCCS-CND is in the standby containment cooling mode of operation. In the reactor pressure vessel (RPV) cooling mode, the PCCS-CND interfaces with the RPV through isolation valves.