Effect of absorbed hydrogen on the stress corrosion cracking (SCC) susceptibility of unirradiated Zircaloy cladding

Amaya, Masaki  ; Fuketa, Toyoshi

Effect of absorbed hydrogen on the stress corrosion cracking (SCC) susceptibility of unirradiated Zircaloy cladding was examined. The data obtained from literatures show that the ratios of SCC threshold stress () to 0.2% yield stress () in unirradiated Zircaloy claddings increase with increasing hydrogen contents below 60 ppm, irrespective of the kind of Zircaloy-2 and -4. Thermodynamic calculations were carried out for the reaction between iodine gas and zirconium containing hydrogen. The results suggested that the reactions hardly occurred at increased hydrogen content and zirconium reacted with iodine gas only below 90 ppm of hydrogen. Since these tendencies correspond to those of the ratios of to on the hydrogen content, it is considered that hydrogen affects the reactions between iodine gas and zirconium and reduces the SCC susceptibility of Zircaloy claddings.