Experimental study of fibrous debris head loss through sump strainer

In a Loss of Coolant Accident (LOCA), fibrous debris produced during the blowdown phase is transported into the sump and becomes an important cause of head loss through the sump strainer affecting the Emergency Core Cooling System (ECCS) performance. In this study, a vertically installed strainer in horizontal flow loop system was designed to generate fibrous beds on the sump strainer and measure the head loss. Fifteen cases with different approaching velocities and quantities of debris were chosen based on the Double-Ended Guillotine (DEG) accident, 31 "pipe break, and RELAP5-3D simulation of a typical 4-loop Pressurized Water Reactor (PWR) to simulate several sizes of LOCA. NUKON fibrous insulation was used as the fibrous debris using Single shredded by commercial leaf shredder used in NUREG/CR-6224 report and Nuclear Energy Institute (NEI) debris preparation protocol. The experimental head loss results were compared to the head loss model in NUREG/CR-6224 report, and issues of porosity and bed thickness were found. For the vertically installed strainer, which has non-uniform debris bed thickness and less porosity than horizontally deposited beds, a modified head loss correlation is suggested. Also, two results from the NEI preparation were compared with the single shredded fibers.