Head Loss Through Fibrous Debris Bed with Different Types of Perforated Strainers



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Safety related issues in Nuclear Power Plants (NPPs) have always been of concern, especially those issues that are related to Light Water Reactors (LWRs) and their Design Basis Accidents (DBA). One of the ongoing issues that has been extensively studied is the Generic Safety Issue GSI-191, which is dedicated to study and resolve the issues that arise after a Loss-Of-Coolant-Accident (LOCA). Fibrous debris produced during the blow-down phase of Loss-of-Coolant Accidents 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. This study was dedicated to measure the pressure drop across randomly accumulated debris bed on the sump strainer along with measuring the debris bed thickness. Two different types of strainers were installed vertically, one at a time, in a horizontal flow loop and the debris bed thickness was measured during the bed build up process and after reaching steady state. Fifteen tests were conducted to determine the head loss difference between the two strainers and to study the characteristics of the debris bed accumulated on each strainer. The results from this experimental study were compared based on the approaching velocity, debris bed thickness, and strainer type. A realistic permeability model for the NUKON fiber glass insulation material was suggested, to be utilized in related applications, the suggested head loss model was compared to other head loss models developed in previous studies. The permeability model was developed from experimental data acquired from approaching velocities in the viscous region. There was no significant head loss difference between the two strainers for the minimum and intermediate range. Based on the experimental data, the head loss difference between the two strainers for the maximum range was about four times higher than the calculated head loss. The flow rate measurement uncertainty was main reason for the difference in the maximum range. There is a probability that the debris bypass could be different between the two strainers, thus, a debris bypass study is required to further investigate this difference.