Assessment of head loss through LOCA-generated debris deposited in PWR fuel assemblies

•Debris flow resistance in fuel assemblies were experimentally studied.•The formation of debris bed in fuel assemblies were observed.•Experimental results were analyzed in details. A loss of coolant accident (LOCA) would generate debris from thermal insulation and other materials within the containment of a pressurized-water reactor (PWR). Some of the debris may pass through the strainer and accumulated on the fuel assembly (FA), causing resistance to flow for core cooling and could inhibit the LTCC capability of the plant. To address this safety issue, a quantitative assessment of the head loss across debris bed accumulated on a full-scale FA under limiting cases has been experimentally studied. Additionally, the formation of debris bed was also observed during tests to analyze its characteristics in different conditions. All tests results indicated that almost all debris was captured on the bottom nozzle (BN) and P-grid. Fiber acted as a critical role to form a filter bed. Fine particles include SiC particulate and chemical precipitate could make a “Compact effect” on debris bed, exerting a significant impact on pressure drop.