Nuclear Engineering ETDs

Publication Date

9-1-2015

Abstract

Generic Safety Issue-191 (GSI-191) was developed by the United States Nuclear Regulatory Commission (U.S. NRC) to assess the effect of debris loading on pressurized water reactor (PWR) emergency core cooling systems (ECCS) sump strainers during a Loss-of-Coolant Accident (LOCA). Potential contributors to the debris loading include latent dirt, fiberglass insulation, paints, epoxies, and chemical products which form when containment surfaces interact with the released reactor coolant. Chemical effects experiments have been completed to assess the potential debris loading contributions of zinc-bearing materials found in the containment building. Zinc-bearing materials in containment include galvanized steel and inorganic zinc-coated steel (IOZ). This research has shown that zinc interacts with post-LOCA containment chemistry to form chemical products including zinc oxide and zinc phosphate, which may become available to transport to the ECCS sump strainers and impair safe operations. A large amount of zinc release from the dissolution of zinc-bearing surfaces in acidic conditions is shown (up to 120 mg/L), and the retrograde solubility of zinc is confirmed, with strong implications during the cool-down phase of a post-LOCA scenario. Zinc phosphate is shown to form rapidly in the chemical environment within post-LOCA containment following the dissolution of containment buffer trisodium phosphate (TSP), and controls the solubility of dissolved zinc (to less than 1 mg/L). The reduction of dissolved zinc concentration from 120 mg/L to less than 1 mg/L through zinc phosphate precipitation may significantly contribute to the debris loading on ECCS sump strainers and increase sump head loss. Zinc is shown to reduce the corrosion and release from aluminum and iron sources in containment, cathodically shielding those sources and reducing the chemical products of iron and aluminum that contribute to the loading on the ECCS sump strainer. Therefore, while a high release of zinc and the resulting zinc-product precipitation is not favorable for ECCS functionality, zinc is shown to reduce the possible contributions of aluminum corrosion products.

Keywords

Zinc, LOCA, PWR, GSI-191, CHLE, Loss of Coolant Accident, Design-basis accident

Sponsors

Southern Nuclear Operating Company Vogtle Electric Generating Plant

Document Type

Thesis

Language

English

Degree Name

Nuclear Engineering

Level of Degree

Masters

Department Name

Nuclear Engineering

First Committee Member (Chair)

Howe, Kerry

Second Committee Member

Cerrato, Jose

Third Committee Member

Busch, Robert

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