Peculiarities of interaction between oxygen and solute/vacancy in commercial-type zirconium-based alloys: A first-principles study

Abstract

Unveiling the interaction between dissolved oxygen and solutes/vacancies during the initial stages of oxide layer formation at microscale is significant for the peculiarities of Zr-based alloys oxidation exposed in PWRs or LWRs. We perform ab-initio calculations of the diluted zirconium-based alloys with dissolved Nb and Sn solutes, vacancy and oxygen atom and discuss the solute-oxygen and vacancy-oxygen binding. Our analysis shows that with increasing content of Nb solutes the attractive interaction between niobium and oxygen becomes much stronger, which results in a decrease in corrosion rate of these alloys at the bre-breakaway regime caused by diffusion of oxygen. An increase in content of Sn in an alloy results in enforce of the repulsive interaction between Sn atom and oxygen, which causing tin-enriched alloys are characterized by an increased corrosion rate. We conclude that the dissolved oxygen can be localized near Nb atom rather than near Sn atom if both impurities are second-nearest neighbors, the dissolved oxygen can capture single vacancy and small vacancy clusters in zirconium matrix. This study provides a deep insight into the details of oxygen segregation in zirconium-based alloys exploited in nuclear-power plants.