An inverse isotope effect was observed for both the solubility and the diffusivity of H in Pd, i.e., the lightest isotope had the highest solubility and lowest diffusivity. For permeation of H isotopes through Pd-alloy membranes when diffusion was the rate-determining step, T was the least permeating isotope. Since the absolute values of H, D and T permeabilities in Pd differed considerably, the effect could be used as a basis for technical isotope separation. Using an experimentally verified mathematical model, a parametric computational study was performed in order to show the net isotope effects in permeate and bleed flows when feeding a technical permeator with various H isotope mixtures under different feed and permeate pressures. The technical feasibility of H isotope permeation as a method for separation was considered with regard to the process control necessary for a single permeator or a cascade.

Hydrogen Isotope Separation by Permeation through Palladium Membranes. M.Glugla, I.R.Cristescu, I.Cristescu, D.Demange: Journal of Nuclear Materials, 2006, 355[1-3], 47-53