Tritium Retention on Stainless Steel Surface Exposed to Plasmas in LHD (II)

Effects of plasma exposure for tritium retention have been studied using both samples of a plasma-exposed stainless steel and a bare stainless steel. It was seen that the plasma-exposed surface was covered with thin deposition layers. Constituent elements of the deposition layers mainly formed metallic oxides except for C and O, but a part of Fe and Mo was a metallic state. Both samples were simultaneously exposed to tritium gas at room temperature with no heat treatment, and a considerable increase in tritium retention was observed for the plasma-exposed sample. In addition, it was clarified that distribution of tritium retention on the plasma-exposed surface was non-uniform even exposure at room temperature. Increase in tritium retention and non-uniformity of tritium distribution were discussed from viewpoints of distribution and chemical states of constituent elements of the deposition layers.