Boiling water reactor plant with hybrid pressure containment cooling

Abstract

A nuclear energy plant housing a boiling water reactor utilizes an isolation condensers with nearly horizontal condenser tubes for both isolation condenser (IC) mode and passive containment cooling system (PCCS) mode, which is entered in response to a loss-of-coolant accident (LOCA). These tubes extend between a cylindrical distributor and a cylindrical collector. In either mode, the reactor vessel is coupled to the cylindrical distributor. Steam reaching the condenser is condensed to water, which flows back to the vessel, providing a cooling effect. In PCCS mode, gas exiting the tubes is trapped and diverted into a wet well. This diversion path is not avialable in IC mode. As a result water exits the tubes more slowly in IC modes in PCCS mode. The water remaining in the tubes during IC mode renders the condenser less efficient. This lower efficiency partially offsets the greater heat exchange in IC mode due to higher temperature differentials and the relatively absence of noncondensable gases. Accordingly, a larger percentage of the condenser area used during PCCS mode can also be used during IC mode. This amounts to a relatively thorough hybrid utilization of the condenser. The result is a dual-function condenser that is smaller, less expensive, more reliable, and more easily maintained than alternative dual-function condensers.