Tritium permeation behavior implanted into pure tungsten and its isotope effect

A first tritium permeation experiment with pure tungsten specimen, which was 25 mum thick, and annealed at 1273 K for 3 h, was successfully carried out using pure tritium ion beam. The deuterium permeation experiment was also carried out using the same tungsten specimen. The permeation of deuterium and tritium at steady state was found to be controlled by diffusion at implantation side and permeation side (DD regime). No significant isotope effect was observed on the steady-state permeation behavior between deuterium and tritium. On the other hand, the isotope effect on the effective diffusion coefficient in tungsten, derived from the analysis of transient permeation behavior, was observed between deuterium and tritium. The result indicates tritium has larger activation energy of effective diffusion than deuterium. It was not inconsistent with the reported isotope effects of diffusion coefficient for bcc metal, to which tungsten belongs. (C) 2001 Elsevier Science B.V. All rights reserved.