The diffusion of 41Ar and 39Ar in single crystals was investigated, after neutron irradiation, by collecting the released Ar in a liquid-N trap (tables 57 and 58). There appeared to be a relationship between the activation energy and the energy barrier for interstitial diffusion. Low diffusivities were found not only after increased neutron doses but also after doping with SrCl2. It was assumed that the trapping of rare gas occurred, and that vacancy clusters acted as trapping centers. The damaged lattice partially recovered during annealing, but numerous clusters remained after prolonged heat treatment at 650C.

Diffusion and Trapping of Argon in Irradiated Ionic Crystals. P.Schmeling: Journal of Physics and Chemistry of Solids, 1967, 28, 1185-96