Long-term corrosion of Zircaloy before and after irradiation

Abstract

Recently analyzed long-term Zircaloy autoclave corrosion data were used to develop new Zircaloy corrosion correlations. Twenty-two different autoclave tests were analyzed. The tests included specimens from 46 different heats, of both Zircaloy-2 and Zircaloy-4. The material conditions included different heat treatments and various prefilms. Approximately 14 500 data points were generated. Maximum exposure time was 10 507 days (∼29 yr) in a 316°C, test and maximum weight gain was 1665 mg/dm 2 (∼114 μm of oxide film) for a 338°C experiment. A single linear post-transition rate constant was determined in tests where maximum corrosion film thicknesses did not exceed ∼30 μm. At the highest temperatures, where oxide film thicknesses in excess of ∼30 μm were generated, the post-transition corrosion data can best be described by two successive linear equations, each active over a different range. Special in-reactor tests demonstrated that accelerated in-reactor effects on corrosion dissipate after growth of an additional oxide film, on the order of the thickness of the pre-transition oxide layer.