STRESS CORROSION CRACKING OF ZIRCONIUM AND ZIRCALOY-4 IN IODINE CONTAINING SOLUTIONS

摘要

The stress corrosion cracking (SCC) susceptibility of zirconium (UNS R60702) and one of its alloys, Zircaloy-4 (UNS R60804), was studied in 10 g/L iodine dissolved in various alcohols: methanol, ethanol, 1-propanol, 1-butanol, 1-pentanol and 1-octanol. SCC was observed in all the systems studied and the crack propagation rate was found to vary depending on the size of the solvent molecule. As the solvent molecular weight increased, the crack propagation rate decreased. Preceding crack propagation, intergranular attack was found in all the solutions tested. The intergranular corrosion rate also varied with the size of the solvent molecule. Since the corrosion rate of Zr single crystals was similar in all the solutions tested, it was concluded that the decrease in both the intergranular attack rate and the crack propagation rate was due to a steric effect, that hindered the access of the corrosive species to the tip of the crack. The surface mobility SCC mechanism accounts for the experimental observations made in the present work.