Hydrogen and deuterium profiling at the surface of zirconium alloys: II. The effects of oxidation

The H( 15N, αγ) 12C and D( 3He, P) α reactions have been used to measure H and D profiles in Zr-2.5 wt% Nb alloys and single crystals of Zr, which were oxidized in different atmospheres after loading with standard amounts of H and D. Although considerable sample to sample variability was found, large H or D peaks were observed in the majority of the specimens, whose position corresponded to enhanced H or D levels immediately below the surface oxide film. The H or D peaks are believed to be the result of interactions between H(D) and oxygen dissolved interstitially in the Zr lattice at the oxidation temperature. The differences observed between the polycrystalline Zr-2.5 wt% Nb alloy and the single crystal samples are ascribed to the different oxygen profiles in these two sets of specimens. Low levels of hydrogen were detected in the oxide films, in agreement with other experiments in the literature that used tritium autoradiography to monitor the transfer of hydrogen or its isotopes through oxide films on zirconium alloys.