Tritium handling experience at TFTR

In December 1993 the high power D-T experimental program on the Tokamak Fusion Test Reactor (TFTR) began. The transit the TFTR from a DOE general use facility to a low hazard category III nuclear facility has been completed successfully. The low hazard nuclear facility designation that the allowable on-site tritium inventory not exceed 50,000 Curies (1 Ci = 37 GBq). This is a TFTR Technical Safety Requirement. Tritium sealed in approved shipping containers does riot count against this inventory limit A second Technical Safety Requirement at TFTR is to have no more than 25,000 Ci at risk in a single location. From December, 1993 through mid-August, 1994 about 20 grams of tritium have been used in two gas injector assemblies and twelve neutral beam tritium injectors. The gas injected into TFTR vacuum is pumped by helium cryo-panels in the four neutral beam boxes. During non-operating periods the cryo-panels are warmed and the hydrogen am released and pumped into gas holding tanks in the tritium area. Gas in the holding tanks is oxidized in the Torus Cleanup System (TCS) and the hydrogen isotopes are collected, as water, on disposable molecular sieve beds (DMSB). These beds are then removed from the system and shipped off-site for tritium recovery or for long-term storage. Several problems in the tritium cleanup systems have occurred following a leak of sulfur hexafluoride (SF6) from a neutral hewn high voltage enclosure ion source and subsequent pumping to the gas holding tanks. These problems included failure of several-moisture sensors, false readings on tritium monitors and, partial loss of catalytic activity in the TCS recombiner. Procedures for dealing with and removing this contaminant gas had to be developed and implemented. The results from this occurrence provide valuable guidance for future tritium burning fusion machines