Direct observation of hydrogen and deuterium in oxide grain boundaries in corroded Zirconium alloys

Atom probe tomography has been used to the study the distribution of hydrogen and deuterium in the oxide scale of two common zirconium alloys after autoclave testing in H2O and D2O, respectively. Comparison between hydrogen and deuterium in the mass spectra allows for separation of hydrogen as a corrosion product from adsorbed H2 gas from the vacuum chamber. Enrichment of hydrogen and deuterium, as OH+ and OD+, was observed in grain boundaries. The grain boundaries were identified through segregation of iron. This lends experimental support to existing theories for the mechanism of hydrogen pick-up in zirconium alloys.