Fusion Science and Technology / Volume 41 / Number 3P2 / May 2002 / Pages 612-616
Device, Facility, and Operation / Proceedings of the Sixth International Conference on Tritium Science and Technology Tsukuba, Japan November 12-16, 2001
Effluent of tritium in vacuum exhaust in JT-60 through the stack to environment always remains a level below detectable level (<10−5Bq/cm3 at the stack, <10−7Bq/cm3 at the site boundary). Though tritium concentration of drain water is below the limit of regulations of the local agreement and the law, small tritium contamination in the facility drain and in the rain drain of stack appeared occasionally. For a scheduled maintenance work of the in-vessel components, following an annual deuterium plasma discharge campaign, a 4-week no-deuterium (H or He) plasma discharge campaign and the succeeded ventilation by room air allow to reduce tritium on the interior surface of in-vessel components. This cleaning up shots and air introduction allowed workers to enter into the vacuum vessel. Air blow well tends to remove surface tritium elements and would be necessary before disassembly and replacement of components on vacuum pumping lines.