High temperature Zircaloy-4 oxidation in water vapour-containing environments examined with Raman imaging and labelled oxygen

• Published in: Corrosion science Vol. 184; p. 109351
• Main Authors: Mermoux, M., Duriez, C., Coindreau, O.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Ltd 15.05.2021; Elsevier BV; Elsevier
• Subjects: A. Zircaloy; B. Spent Fuel Pool; C. Raman spectroscopy; Chemical Sciences; D. Gas/surface exchange; Gas mixtures; Gas-solid interfaces; High temperature; Mass spectrometry; Oxidation; Oxygen; Thermogravimetry; Water vapor; Zircaloys (trademark); Zirconium dioxide; B. Spent Fuel Pool; C. Raman spectroscopy; A. Zircaloy; D. Gas/surface exchange; Zircaloy; Raman spectroscopy; Gas/surface exchange; Spent Fuel Pool
• ISSN: 0010-938X; 1879-0496
• DOI: 10.1016/j.corsci.2021.109351

•Zircaloy-4 high temperature oxidation was studied in labelled N2–18O2–H216O atmospheres.•18O-tracer distributions in zirconia were analysed on cross sections by Raman imaging.•In the pre-transition regime, mostly steam contributes to the zirconia scale growth.•In the nitrogen-catalysed regime, both oxidizing species contribute to oxidation.•Competitive adsorption of oxygen and steam are proposed to trigger the oxidation mechanisms. High Temperature oxidation of Zircaloy-4 was studied in N2–O2–H2O gas mixtures using labelled 18O2, thermogravimetry, Raman imaging and mass spectrometry. Samples were either exposed to N2–18O2–H2O gas mixtures, or two-stage oxidised first in 18O2, then in H216O - N2 or 16O2 - N2 atmospheres. In the pre-transition, diffusion-controlled regime, mostly steam contributes to the zirconia formation, while in the nitrogen-catalysed post transition regime both oxygen and steam contribute to the oxidation. These results were tentatively explained by competitive adsorption of oxygen and steam at the gas/solid interfaces, and the formation of porosity in the oxide layers.