In the event of a loss-of-coolant accident within the containment of a pressurized water reactor (PWR), piping thermal insulation and other materials in the vicinity of the break will be dislodged by break jet impingement. A series of tests was conducted on two different closed-loop test setups that were specifically designed to study the accumulation of debris and the consequent head loss across sump screens in PWRs. This paper addresses issues related to accumulation of transported debris on the sump screen and the consequent head loss. New test data that provide insights on head loss across a debris bed consisting of fragments of calcium silicate were generated.