GSI-191: Separate-Effects Characterization of Debris Transport in Water (NUREG/CR-6772)

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Publication Information

Manuscript Completed: December 2001
Date Published: August 2002

Prepared by:
D. V. Rao, B. C. Letellier
A. K. Maji,* B. Marshall*

Los Alamos National Laboratory
Los Alamos, NM 87545

Subcontractors:
*University of New Mexico
Department of Civil Engineering
Albuquerque, NM 87110

M. L. Marshall, 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 the results of experiments conducted, as part of the resolution of the Nuclear Regulatory Commission (NRC) Generic-Safety-Issue (GSI) 191, to measure specific debris transport properties for a selection of potential types of debris. The purpose of the GSI-191 study is to determine if the transport and accumulation of debris in a containment following a loss-of-coolant accident (LOCA) will impede the operation of the ECCS in operating PWRs. In the event of a LOCA within the containment of a PWR, thermal insulation and other materials in the vicinity of the break will be damaged and dislodged. A fraction of this material would be transported to the recirculation (or emergency) sump and accumulate on the screen thereby forming a debris bed. Excessive head loss across this bed could prevent or impede the flow of water into the core or containment.

The properties measured by these experiments included: 1) the terminal settling velocity in quiescent pools and in water pools in planar motions, 2) the minimum fluid velocity at which an individual stationary fragment resting on the containment floor would begin to move, 3) the minimum fluid velocity required to induce "bulkscale" movement of a population of debris fragments, and 4) the minimum fluid velocity required to lift a fragment of debris over a vertical curb that impedes forward motion along the floor. In all cases, these velocities were measured in terms of the pool average velocity. Experiments were also conducted to examine the variability in transport properties due to flow turbulence.