Reagent-grade, OH--doped crystals were studied at temperatures of between 550 and 750C. It was found that the activation energy for diffusion was equal to 1.82eV. This agreed with estimates that were based upon vacancy-pair calculations.

Diffusion and Solution of Cl2 in KCl. T.Ikeda: Journal of the Physical Society of Japan, 1980, 49[6], 2227-30