Long-term corrosion of Zircaloy before and after irradiation

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 (similar to 29 yr) in a 316 degrees C, test and maximum weight gain was 1665 mg/dm(2) (similar to 114 mu m of oxide film) for a 338 degrees C experiment. A single linear post-transition rate constant was determined in tests where maximum corrosion film thicknesses did not exceed similar to 30 mu m. At the highest temperatures, where oxide him thicknesses in excess of similar to 30 mu m 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. (C) 2000 Elsevier Science B.V. All rights reserved.