EXPERIMENTAL STUDIES OF THE CHEMICAL EFFECTS OF ZINC-BEARING MATERIALS FOLLOWING A LOSS-OF-COOLANT ACCIDENT IN A PRESSURIZED WATER REACTOR

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

Iron Behaving Badly: Inappropriate Iron Chelation as a Major Contributor to the Aetiology of Vascular and Other Progressive Inflammatory and Degenerative Diseases

The production of peroxide and superoxide is an inevitable consequence of aerobic metabolism, and while these particular "reactive oxygen species" (ROSs) can exhibit a number of biological effects, they are not of themselves excessively reactive and thus they are not especially damaging at physiological concentrations. However, their reactions with poorly liganded iron species can lead to the catalytic production of the very reactive and dangerous hydroxyl radical, which is exceptionally damaging, and a major cause of chronic inflammation. We review the considerable and wide-ranging evidence for the involvement of this combination of (su)peroxide and poorly liganded iron in a large number of physiological and indeed pathological processes and inflammatory disorders, especially those involving the progressive degradation of cellular and organismal performance. These diseases share a great many similarities and thus might be considered to have a common cause (i.e. iron-catalysed free radical and especially hydroxyl radical generation). The studies reviewed include those focused on a series of cardiovascular, metabolic and neurological diseases, where iron can be found at the sites of plaques and lesions, as well as studies showing the significance of iron to aging and longevity. The effective chelation of iron by natural or synthetic ligands is thus of major physiological (and potentially therapeutic) importance. As systems properties, we need to recognise that physiological observables have multiple molecular causes, and studying them in isolation leads to inconsistent patterns of apparent causality when it is the simultaneous combination of multiple factors that is responsible. This explains, for instance, the decidedly mixed effects of antioxidants that have been observed, etc...Comment: 159 pages, including 9 Figs and 2184 reference

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