Tritium permeation behavior implanted into pure tungsten and its isotope effect

Nakamura, Hirofumi; Hayashi, Takumi; Kakuta, Toshiya*; Suzuki, Takumi; Nishi, Masataka

The isotope effect on the implantation-driven permeation of pure tritium (T) and deuterium (D) through nickel was investigated, respectively. The rate-determining processes of backward flow at the upstream surface and permeation at the down-stream surface were found to be as follows: recombination on up-stream surface and diffusion at down-stream side in a lower temperature region, whereas recombination on both surfaces in a higher temperature region for T and D, respectively. The diffusion coefficients of T and D derived by analyzing the obtained transient data of permeation in the lower temperature region were in good agreement with literature data of deuterium. The obtained activation energy of diffusion for T and D suggested the tendency of mass dependence. The surface recombination coefficients for both isotopes were also derived and showed in good agreement with literature data. As a result, the experimental results indicated the surface recombination could be attributed to the isotope effect of the permeation between T and D rather than the diffusion.