Abstract
The tritium effluent of JT-60 vacuum exhaust through the stack and into the environment always remains below the detectable level. Tritium concentration in the drain water is below a limit of regulation by the local agreement and the law, though small tritium contamination in facility drains and in rain drains of the stack has occasionally been detected. Following an annual deuterium plasma discharge campaign, a 4-week hydrogen or helium plasma discharge campaign and subsequent ventilation of room air reduced the tritium concentration on the surface of in-vessel components back to ground level and then the in-vessel was ready for the maintenance. A cooperative endeavor is underway to complete an analysis of tritium behaviors in JT-60.
