The Oxidation of Pure Zirconium in Steam from 1000° to 1416°C

Abstract

The oxidation of pure, arc‐melted crystal‐bar zirconium in steam was studied over the temperature range 1000°–1416°C. The early stages of the reaction at all temperatures investigated above 1000° C were characterized by uniform parabolic growth of layers of zirconium oxide and oxygen‐stabilized alpha zirconium. Parabolic rate constants were determined for the growth of each layer, and these served as a basis for the calculation of effective chemical diffusion coefficients for oxygen in the growing product phases. These calculations were made on the assumption that this system may be described as an ideal, multiphase, moving boundary diffusion problem. The results and their comparisons with similar data for the oxidation of Zircaloy‐4 indicate that this diffusion model is accurate over the temperature range involved. At 1000°C, however, departures from ideal kinetics were observed that were attributed to structural changes in the oxide layer during the course of the reaction.