Gravity-driven core flooding system

The gravity-driven core flooding system consists of a pipe connecting the containment pool to the reactor cold leg coolant piping. A check valve permits the reactor to operate... 

To ensure long-term decay heat removal in the event of a piping breach within the containment building steam tunnel, the volume of the containment pool exceeds that of the steam tunnel. Because of the seal between the reactor and steam tonnel floor, coolant will accumulate within the steam tunnel, with steam condensed and retorned to the containment pool. With the steam tunnel filled with water from the containment pool, a sufficient level will remain in the containment pool to cover both the suppression nozzles and the gravity-driven core flooding system inlet pipe. This featore eliminates the need for an active pumping system and other related components (eg, sump strainers). 

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