A comparison of thermo-oxidation kinetic measurements of Zircaloy-4 in light and heavy water steam

High temperature oxidation experiments of Zircaloy-4 have been previously reported using various gaseous environments including light water steam and synthetic air, but no experiments involving heavy water steam oxidation have been reported in the open literature. Understanding the reaction kinetics in heavy water steam is important for CANDU nuclear generating stations, which are moderated and cooled by heavy water. The long standing assumption has been that the oxidation behaviour is the same for both environments; the objective of this work is to validate that assumption. The oxidation behaviour of Zircaloy-4 was investigated in this work under light water steam and heavy water steam to compare the reaction kinetics at temperatures ranging from 500 ∘C to 1250 ∘C to simulate an accident scenario. For this work, a NETZSCH 449 F1 Simultaneous Thermal Analyzer was used to perform thermogravimetric measurements of Zircaloy-4 specimens to measure the mass changes and oxidation reaction rates. A comparison was then drawn and benchmarked to available data in the open literature for similar experiments. Additionally, Scanning Electron Microscopy and Energy-dispersive X-Ray Spectroscopy analyses were performed for a few specimens to analyse and identify oxidation behaviour over the specified temperature range.