Hydrogen traps in ion-irradiated F82H steel observed by NRA

Characteristics of irradiation-induced trapping of hydrogen were investigated for quantitative evaluation of tritium retention in F82H steel. Before and after irradiation of 0.8-MeV 4He or 0.3-MeV H ions, deuterium depth profiles near the surface of a disk sample were observed by nuclear reaction analysis under continuous exposure of deuterium plasma. One type of trap, with a trapping energy of 0.66 eV, was observed after each irradiation. The ratio of trap production rate to atomic displacement was 0.0046 and 0.0014 for He and H irradiation, respectively. Annihilation occurred around 600 K for H irradiation but was not observed even at 691 K for He irradiation. Traps are likely to be interstitial-like sites associated with dislocation loops. This study also indicates that helium plays a role in inhibiting trap annihilation. In addition, the deuterium diffusion coefficient in non-irradiated F82H was determined by a time-lag permeation experiment.