United States Nuclear Regulatory Commission - Protecting People and the Environment

GSI-191: Experimental Studies of Loss-of-Coolant-Accident-Generated Debris Accumulation and Head Loss with Emphasis on the Effects of Calcium Silicate Insulation (NUREG/CR-6874, LA-UR-04-1227)

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Publication Information

Manuscript Completed: April 2004
Date Published:
May 2005

Prepared by:
C.J. Shaffer1, M.T. Leonard2, B.C. Letellier, D.V. Rao,
A.K. Maji3, K. Howe3, A. Ghosh3, J. Garcia3, W.A. Roesch,
J.D. Madrid

Principal Contractor:
Los Alamos National Laboratory
Los Alamos, New Mexico 87545
1Subcontractor:
ARES Corporation
Albuquerque, New Mexico 87106
   
2Subcontractor:
dycoda, LLC
Belen, New Mexico 87002
3Subcontractor:
Department of Civil Engineering
University of New Mexico
Albuquerque, New Mexico 87110

T.Y. Chang, NRC Project Manager

Prepared for:
Division of Engineering Technology
Office of Nuclear Regulatory Research
U.S. Nuclear Regulatory Commission
Washington, DC 20555-0001

NRC Job Code Y6041

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Abstract

This report documents experiments conducted to determine the head-loss characteristics associated with calcium silicate insulation debris accumulated on a sump screen. These experiments were performed under the direction of Los Alamos National Laboratory in facilities operated by the Civil Engineering Department of the University of New Mexico. Experiments confirmed that calcium silicate insulation could degenerate into very fine particulates in the containment environment after the occurrence of a loss-of-coolant accident (LOCA), and that debris beds formed by a combination of fine calcium silicate particulates and fibrous insulation on a sump screen can cause substantial head loss across the sump screen. Recommended head-loss parameters to be used in the NUREG/CR-6224 correlation were established with consideration of uncertainties in test parameters and variability in the manufacture of the particular brand of calcium silicate insulation tested. Using these recommended input parameters (e.g., specific surface area and particle density), the NUREG/CR-6224 correlation predicts reasonably well conservative head losses as demonstrated by comparisons with experimental data obtained in this study. Debris accumulation on a simulated (vertical) pressurized-water reactor (PWR) sump screen was examined for several different types of LOCA-generated debris, including shredded fiberglass, crushed calcium silicate insulation, mixtures of NUKON™ and calcium silicate, and crumpled stainless-steel foils from the interior of reflective metal insulation. Results from this research enhance the understanding of head-loss characteristics important to the resolution of Generic Safety Issue 191, “Assessment of Debris Accumulation on PWR Sump Performance.”

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