High temperature Zircaloy-4 oxidation in water vapour-containing environments examined with Raman imaging and labelled oxygen. (15th May 2021)

• Record Type: Journal Article
• Authors: Mermoux, M.; Duriez, C.; Coindreau, O.
• Is Part Of: Corrosion science. Volume 184(2021)
• Publication Date: 2021-05-15
• Subjects: A. Zircaloy -- B. Spent Fuel Pool -- C. Raman spectroscopy -- D. Gas/surface exchange; Corrosion and anti-corrosives -- Periodicals; 620.11223
• DOI: 10.1016/j.corsci.2021.109351
• Languages: English
• ISSNs: 0010-938X

Abstract

Highlights: Zircaloy-4 high temperature oxidation was studied in labelled N2 – 18 O2 –H2 16 O atmospheres. 18 O-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. Abstract: High Temperature oxidation of Zircaloy-4 was studied in N2 –O2 –H2 O gas mixtures using labelled 18 O2, thermogravimetry, Raman imaging and mass spectrometry. Samples were either exposed to N2 – 18 O2 –H2 O gas mixtures, or two-stage oxidised first in 18 O2, then in H2 16 O - N2 or 16 O2 - 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.