An investigation was made of the kinetics of inert gas release from undoped and U-doped (0.05at%U) single crystals, following irradiation to an integrated thermal flux of about 1016/cm2, using charcoal traps in a vacuum apparatus and activity measurements of the released gas. The 88Kr diffusion results for 600 to 850C could be described by:

D (cm2/s) = 1 x 105 exp[-2.6(eV)/kT]

Those for temperatures ranging from 900 to 1200C could be described by:

D (cm2/s) = 4 exp[-1.5(eV)/kT] It was suggested that the rare gas atoms moved independently of both ions of the host lattice, and made use of those diffusion sites (interstitial sites) which were available in the highest concentration.

Rare Gas Diffusion in Alkaline-Earth Fluorides (Kr, Xe in SrF2, BaF2). F.W.Felix, S.Y.T.Lagerwall: Physica Status Solidi B, 1969, 33[1], 85-9