Rare gas diffusion in alkali metal iodides

Abstract

Xenon‐133 diffusion coefficients were measured in single crystals of KI, RbI, and CsI over the temperature range of 150 to 500 °C. Xenon was incorporated in the crystals both by doping with precursor I133 and by fission recoil from an external fissionable source. Consistent diffusion results were obtained which yielded single values for the diffusion activation energy over the temperature range of measurement. A gas concentration effect which was attributed to gas atom clustering was observed at concentrations as low as 10−9 gas atom fraction. Diffusion results were found to be most consistent with a model in which gas atoms associate with mobile defect clusters and diffuse with the clusters through the crystal lattice.

Diffusion d'ESPÈCES Atomiques Et Ioniquesrare Gas Atoms in Ionic Crystals : Methods, Results and Application to the Study of Lattice Defects

“…This method has been used already in 1942 by Zin~en to investigate AgJ after precipitation from a fission iodine containing solution [3]. Recently, Mears and Elleman [4] made an extensive study of Xe-133 mobility in crystals of tlie alkaliiodides, which were grown from a melt containing the fission product I-133.…”

“…Such a gas-gas-interaction has not yet been found in any neutron irradiated system where the gas is assumed to move interstitially (e. g. in any multi-gas diffusion experiment Ar, Kr and Xe always diffused independently, regardless of the relative gas concentrations). A useful attempt ro clearly separate gas-and trap-concentration contributions was made by Mears and Elleman [4] by using the 1-133 doping method (see section 2.2.1). Unfortunately are the given results not sufficient to decide for or against a gas-concentration effect.…”