Pressure Drop and Filtration through Fibrous Porous Media on the Sump Strainer of Light Water Reactors

Fibrous porous media has been found in a variety of industrial applications including filters and insulation materials. In nuclear power plants, fibrous media are found as insulation materials to prevent heat loss and protect the containment structures and other components from thermal effects. However, in spite of efficient thermal insulation, fibrous media have been focused on as a hazard in the Emergency Core Cooling Systems (ECCSs). Fibrous debris generated from fiberglass insulation materials during a Loss of Coolant Accident (LOCA) might accumulate on the containment sump strainer causing loss of Net Positive Suction Head (NPSH), called the upstream effect, or it might penetrate through the strainer becoming a source of clogging for flow channels in the core (downstream effect). In the present work, head loss through fibrous porous media made of the same fiberglass insulation material used in pressurized water reactors (PWRs) were experimentally investigated to study upstream effects. Porosity of fibrous porous media was also considered by measuring build-up of debris beds. In order to study downstream effects, quantity of debris bypass was examined by changing the type of water, concentration of debris, fluid approach velocity, and temperature. As results, a head loss model, a compression model, and a debris bypass model were proposed for the given conditions in this study. Additionally, a microscope system was developed to characterize size distribution of irregular-shaped fibrous debris. The methodology was applied to three samples and the maximum fraction of debris bypass was found in the size range of 10 to 250 ?m.