Influence of Alkali Metal Oxides and Alkaline Earth Metal Oxides on the Mitigation of Stress Corrosion Cracking in CANDU Fuel Sheathing

Abstract

Stress corrosion cracking (SCC) can cause failures of CANDU® Zircaloy-4 fuel sheathing. The process occurs when a corrosive element (i.e.,iodine) interacts with a susceptible material that is under sufficient strain at a high temperature. Currently, there is an ongoing effort to improve SCC mitigation strategies for future iterations of CANDU reactors. A potential mechanism for SCC mitigation involves utilizing alkali metal oxides and alkaline earth metal oxides that will sequester corrosive iodine while actively repairing a protective oxide layer on the sheath. SCC tests performed with sodium oxide (Na₂O) and calcium oxide (CaO) have shown to decrease significantly the sheath degradation.