Hydrogen permeation in metals near room temperature by a tritium tracer technique

{In a fusion reactor, tritium retention and permeation in structure materials are very important safety concerns. Most data for diffusion and permeation of hydrogen in metals so far available have been limited for rather higher temperatures and, in particular, no data are available for high-Z metals near room temperature (RT). We have tried to observe gaseous hydrogen permeation through metals near RT applying a tritium tracer technique, which is a very powerful tool to detect quite small amount of hydrogen (tritium) by a liquid scintillation counting (LSC) method. After confirming the reliability of the method for the determination of diffusion and permeation coefficients in pure Ni, it was applied to hydrogen permeation in W near RT, and diffusion and permeation coefficients of hydrogen in W were determined