Hydrogen in nano-voids in neutron-irradiated nickel was detected using positron annihilation lifetime spectroscopy (PALS). As positron lifetime was greatly affected by nano-voids bound with hydrogen, special attention was paid to the analysis. The positron lifetime of neutron-irradiated nickel at higher irradiation doses increased with the dose, which was an indicator for vacancy cluster (nano-void) formation in the lattice. The introduction of hydrogen in well-annealed nickel by electrical charging also resulted in an increase in positron lifetime due to vacancy formation. In neutron-irradiated nickel specimens, hydrogen charging shortened the positron lifetime from 456 to 334 ps (irradiation dose: 3 x 10-3dpa). Isochronal annealing behaviour of hydrogen-charged nickel and neutron-irradiated nickel was also studied. Positron trapping rate was calculated using a simple trapping model. Thermal desorption spectroscopy was used for the investigation of hydrogen behaviour in non-irradiated hydrogen-charged nickel.

Detection of Hydrogen in Neutron-Irradiated Nickel using Positron Lifetime Spectroscopy. C.He, T.Yoshiie, Q.Xu, K.Sato, S.Peneva, T.D.Troev: Philosophical Magazine, 2009, 89[14], 1183-95