Isotope effects in metal-hydrogen systems

Isotope effects in pure isotope systems are reviewed. Both the solubility and the mobility of hydrogen isotopes in metals and alloys are considered. Mixed isotope systems are then discussed, with particular emphasis on tracer techniques such as tritium tracer exchange and diffusion. The tritium tracer diffusion technique is briefly explained. A theoretical treatment of the diffusion of a tracer isotope mixture in the presence of traps is described. This method is used to determine (i) the trap binding energy and the trap binding entropy, (ii) the protium-tritium separation factor for trap sites and interstitial sites and (iii) the trap concentration in cold-rolled palladium. It is shown that dislocations act as traps in this material. Finally some practical aspects of the separation of isotopes by permeation techniques and the prediction of large isotope effects are discussed. (Auth.)