Measurements were made of post-irradiation inert-gas release from single crystals of pure and U-doped material. The activation energy was equal to 4eV (figure 31), for the diffusion of 88Kr in U-doped single crystals after irradiation. This low value, and the fact that the activation energy did not depend upon the atomic size, indicated that transport did not proceed via an interstitial mechanism.

J.Biersack, A.Brenner: Nukleonik, 1967, 10[5], 264-7

Figure 31

Diffusion of 88Kr in CaF2