There is a concern that coolant containing debris, specifically crushed pieces of thermal insulation, paint chips, and chemical precipitates, generated in a loss of coolant accident, which is one of the design basis accidents of a PWR, will be fed into the reactor vessel during recirculation operations and the debris will block the cooling flow paths at the core inlet, resulting in an inhibition of the removal of core decay heat. Regarding this concern, the flow test was carried out by using a system with two full-scale fuel assemblies and it was verified that the effect of debris on the cooling flow path blockage was negligible, and subsequently conducted a thermal-hydraulic analysis based on the test results to clarify that sufficient coolant was supplied to the core and the core decay heat was properly removed.
