Behavior of Tritium near Surface Region of Metals Exposed to Tritium Plasma

In order to understand behavior of tritium (T) on surface and in bulk of metals exposed to T plasma, both surface activities and depth profiles of T were periodically observed by a tritium imaging plate technique during storage in air at room temperature (RT) for over 1 year. In the T depth profiles, T localized within a depth of sub mm from the surface was clearly distinguished from T in the bulk. The former was attributed to strong trapping by some defects produced by the plasma exposure and remained quite longer during the storage, while the latter was released from the surfaces by diffusion. T surface activity measured on the plasma-exposed surface changed in a complicated way with time due to removal of T by isotopic replacement with H in ubiquitous H₂O and T supply from the bulk in the course of the diffusional release.