General Corrosion of Materials under Simulated BWR Primary Water Conditions.

概要

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General corrosion tests of Type 304SS, Alloy X750 and Stellite #6 used for BWR primary component materials were performed under various conditions of simulated BWR primary water. The authors' interest was focused on the corrosion behavior, such as metal release and the buildup of corrosion oxide film. It was possible to recognize these corrosion behaviors from the nature of the oxide film of which morphology and property depended on the tested corrosion environment; (1) The metal release of chromium and iron, the elemental composition of the corrosion oxide films, and electrochemical potentials (ECPs) depended on the oxygen concentration in the test environment. (2) The corrosion rate of Type 304SS showed its minimum value in a passive region around 0 mV vs standard hydrogen electrode (SHE). It increased slightly by γ-ray irradiation for normal water chemistry (NWC) and it became 2 times for hydrogen water chemistry (HWC). (3) The corrosion rates of Alloy X750 and Stellite #6 were over 4 times that of Type 304SS in oxygenated environments such as in-core water containing H2O2. (4) The differences in the corrosion rates among these alloys were due to the nature of the oxides determined from the composition of the base alloys and the tested corrosion environments.