Experimental study of debris head loss through a pressurized water reactor recirculation sump screen after LOCA

A loss of coolant accident (LOCA) in a PWR (pressurized water reactor) would generate debris from thermal insulation and other materials in the vicinity of the break. A fraction of the LOCA-generated debris and pre-LOCA debris would be transported into the sump and accumulated on the sump screens resulting in adverse blockage effects that include decrease in net positive suction head (NPSH) margin. The NUREG/CR-6224 head loss correlation has been widely used to estimate debris-induced head loss across sump screens, but it has been recommended to be used for debris thicknesses less than 4 in. In order to extend the limit, head loss data are obtained over a wider range of bed thicknesses. Experimental results show that the NUREG/CR-6224 correlation conservatively predicts the head loss across NUKON™ debris beds with theoretical thicknesses up to 6 in. Head loss measurements in mixed debris beds show that fibrous debris with calcium-silicate and/or fine particulates such as coatings mainly deteriorates the NPSH.