Hydrogen isotope separation by permeation through palladium membranes

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