Hydraulic Transport of Coating Debris (NUREG/CR-6916)
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Manuscript Completed: October 2006
Date Published: December 2006
Principal Investigators: T. Fu and A. Fullerton1
A. Fullerton, T. Fu, D. Walker and J. Carneal1
1Naval Surface Warfare Center, Carderock Division
9500 MacArthur Boulevard
West Bethesda, MD 20817
2Pacific Northwest National Laboratory
902 Battelle Boulevard
Richland, WA 99352
E. Geiger, NRC Project Manager
Division of Fuel, Engineering and Radiological Research
Office of Nuclear Regulatory Research
U.S. Nuclear Regulatory Commission
Washington, DC 20555-0001
NRC Job Code N-6198
Generic Safety Issue (GSI)-191 "Assessment of Debris Accumulation on PWR Sump Performance" raised the concern of debris transport to pressurized-water-reactor (PWR) sump screens following a loss-of-coolant accident (LOCA) and subsequent impact to emergency core cooling systems (ECCS) and containment spray systems (CSS) during ECCS sump recirculation. Failed coatings debris is one potential source for debris transported to the ECCS sump screens. This document describes a limited number of tests conducted to study the transportability of coatings debris (chips) in ambient temperature water, at specific conditions of uniform flow. It is intended that the transport parameters observed in these tests could be used as the basis for the evaluation of coating chip transport under plant specific conditions. The transport characteristics of coatings particulates were not examined in these experiments as fine particulate are assumed to transport.
Five coating systems, typical of coatings applied to equipment and structures located in the contaminant buildings of PWR plants, were tested. The effects of chip size, shape, density, thickness, stream velocity, water saturation, and thermal curing on transportability were examined through two types of tests – quiescent settling and transport within uniform flow. The quiescent settling tests were conducted in a 0.3 m wide by 0.3 m long by 1.2 m deep (one foot wide by one foot long by four foot deep) acrylic tank. The goals of the quiescent water tests were to determine: (1) the time necessary for coating chips dropped onto the water surface to break the surface and begin to sink (time-to-sink tests), and (2) to determine the terminal settling velocity of submerged coating chips (terminal velocity tests). The transport tests were conducted in a 0.91 m wide by 0.91 m deep by 9.1 m long (three foot wide by three foot deep by thirty foot long) acrylic flume suspended in a large circulating water channel. The goal of the transport tests was to characterize the behavior of coating chips in moving water. The tests consisted of a tumbling-velocity test to study the behavior of coating chips placed on the flume floor and a steady-state velocity test to study the behavior of coatings debris released into the moving stream below the water surface. A statistically meaningful number of data tests were conducted for each coating type, chip size and chip shape in each test category in order to more accurately quantify observations.
The quiescent tests demonstrated that, when dropped onto the water surface, coating chips with a density close to that of water tended to remain on the surface indefinitely and heavier chips tended to sink almost immediately. The tumbling velocity tests demonstrated that all but the lightest chips and curled chips remained in their initial position at stream velocities in excess of 0.09 m/s (0.3 ft/s). The steady-state velocity test demonstrated that, at a uniform water velocity of 0.06 m/s (0.2 ft/s), all but the lightest chips settled to the bottom before reaching the end of the flume.