Small-Scale Experiments: Effects of Chemical Reactions on Debris-Bed Head Loss — A Subtask of GSI-191(NUREG/CR-6868,LA-UR-03-6415)

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Publication Information

Manuscript Completed: November 2003
Date Published: March 2005

Prepared by:
R.C. Johns, B.C. Letellier (Principal Investigator)
Los Alamos National Laboratory
Los Alamos, New Mexico 87545

K.J. Howe, A.K. Ghosh
Department of Civil Engineering
University of New Mexico (Subcontractor)
Albuquerque, NM 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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Small-scale head-loss flow tests and quiescent-immersion corrosion tests were performed to determine whether post-loss-of-coolant-accident debris generation and sump-screen head loss in a pressurized-water-reactor containment system can be affected by chemical interactions between the emergency-core-cooling-system water, which contains boric acid and sodium hydroxide at elevated temperatures, and (1) exposed metal surfaces, (2) inorganic zinc-based paint chips, and (3) fiberglass insulation debris. The principal findings of this study are that: (1) temperature-dependent corrosion of zinc metal can occur at typical temperatures and pH; (2) precipitation of dissolved iron, aluminum, and zinc in excess of their low solubility limits produces transportable gelatinous material that can cause additional pressure drops across a fibrous debris bed; (3) dissolved zinc can be leached from zinc-based coatings debris; and (4) silica can be leached from typical fiberglass insulation debris and may be an important constituent of the chemical system. However, the implied progression from metal corrosion to the ultimate precipitation of a flocculent material was not demonstrated conclusively. One alternative corrosion product observed in the zinc immersion tests was a crystalline surface growth, suggesting redeposition of zinc compounds initiated in a saturated solution. Electron microscopy, energy dispersive spectrometry, and x-ray diffraction methods were employed to determine the composition of the surface corrosion product.