Simulation of the loss of residual heat removal events during mid-loop operations

Over the years, a number of loss of decay heat removal events have occurred in different Pressurized Water Reactors (PWRs) in the US while the reactor coolant system (RCS) is partially drained to near mid-loop levels. This paper presents the results of the thermal-hydraulic analyses performed for Westinghouse PWRs to predict the RCS behavior following the loss of residual heat removal for various RCS configurations possible during these mid-loop operations. RCS configuration constraints, minimum equipment availability and other operational considerations necessary to ensure a coolable core geometry are also discussed