The barrier properties of ZrO2 to inward migration of deuterium have been investigated with a view to understanding the hydriding mechanisms of a Zr‐2.5% Nb alloy used in CANDU nuclear reactors fuel channels. Thin film oxide specimens, grown in steam to ∼1 μm thickness, have been heated to 350 °C and exposed to deuterium gas at pressures ranging from 6×103 Pa to 101 kPa (1 atm) and times from 10 to 810 min. Some irreversible uptake can be measured for all exposures using secondary ion mass spectrometry. At low exposures, the shape of the deuterium concentration profile is can be fitted to a Fickian relationship. During longer exposures, the rate of deuterium ingress is sharply curtailed, presumably due to passivated outer oxide surface. Reactions between D2O vapor and the thin film oxide in the 103 Pa pressure region and above show a sharply higher uptake of deuterium than in the equivalent pressure of D2 gas. This is ascribed to a more efficient decomposition of D2O on the ZrO2 surface compared to D2.

This content is only available via PDF.
You do not currently have access to this content.