Tritium release from Zircaloy-2: Dependence on temperature,surface conditions and composition of surrounding medium

Tritium release of tritiated and partially oxidized Zircaloy samples using reactive and inert carrier gases was studied in a temperature range from 200 up to 600°C. For commercial rolled foils, covered by a ? 0.1 μm thick oxide layer, the release rates increased by 5 orders of magnitude in the investigated temperature interval. Released tritium appears at low temperatures preferentially as HTO, even if there are only a few ppm oxygen present in the carrier gas. Furthermore, the effect of the thickness of the oxide layer on the release rates was studied. At lower temperatures the release rates are correlated with the thickness of the layer. However, this was not very evident at 500°C due to the influence of oxygen diffusion.