Measurements were made of the release of 41Ar and 39Ar from fast neutron-irradiated (greater than 1015/cm2) single crystals. Diffusion at temperatures ranging from about two-thirds of the absolute melting point to the melting point itself occurred via an interstitial mechanism. The diffusivity at the melting point of 954K was 10-4cm2/s. The results for temperatures ranging from 425 to 705K could be described by:

D (cm2/s) = 30 exp[-0.97(eV)/kT]

The results for temperatures ranging from 705 to 954K could be described by:

D (cm2/s) = 2 x 10-3 exp[-0.30(eV)/kT]

The higher temperature dependence of the diffusion at lower temperatures was attributed to the trapping effect of intrinsic defects. At higher radiation doses, new release effects were observed; thus indicating the presence of extrinsic and probably clustered defects. Rare-Gas Diffusion in Neutron-Irradiated Potassium Halides. F.W.Felix: Proceedings of the British Ceramic Society, 1967, 9, 273-7