RELAP5-3D Simulation of Core Flow Paths during a Hypothetical Debris-Generated Core Blockage Scenario

摘要

The Emergency Core Cooling System (ECCS) of a Light Water Reactor is designed to supply cooling water for heat removal after the reactor scram during a Loss of Coolant Accident (LOCA). In a later phase of the Pressurized Water Reactor (PWR) accident, when the water of the Refueling Water Storage Tank (RWST) is depleted, cooling continues via recirculation of containment sump water that was discharged from both the break and sprays. This phase is often identified as long-term cooling. Debris created during the blow-down phase could reach to the containment sump and degrade ECCS long-term cooling capabilities . A set of sump screens is typically installed for each ECCS train to reduce debris transport to the primary system and to minimize associated downstream effects that could adversely impact core cooling. In particular, debris may be transported by the coolant inside the reactor vessel and reach the core. The accumulation of debris in the core may produce flow restrictions, additional pressure drops and coolant flow reduction, which, in turn, may degrade the core cooling capabilities.