In the summer and fall of 1996, after nearly three years of D-T operations, TFTR underwent an extended outage during which large port covers were removed from the vacuum vessel in order to complete upgrades to the tokamak. A three tier system was developed for the outage to reduce and control the free tritium in the vacuum vessel in order to minimize the exposure to personnel during port cover removal and reinstallation. The first phase of the program to reduce the free tritium consisted of direct flowthrough of room air through the vacuum vessel to the molecular sieve beds using the Torus Cleanup System. Real time measurements of the effluent tritium concentration were used to derive the amount of tritium removed from the torus. Once the free tritium had been reduced to approximately 50 Ci, a 55 Gallon Drum Bubbler System was used for the direct processing of the vacuum vessel to further lower the tritium level in the torus. Tritium oxide is absorbed by the bubbler system with the exhaust vented to one of the monitored HVAC stacks. To preclude the release of tritium to the Test Cell and to minimize the exposure of workers, a variable flow exhaust system was employed in order to maintain a negative pressure in the vacuum vessel between 0.05 and 0.5 inches-water during removal of port covers ranging in size from approximately 5 to 1000 in². These systems were completely successful in reducing and controlling the free tritium in TFTR and were instrumental in maintaining ALARA during the 1996 outage. These systems are again being utilized during the safe shutdown and decommissioning of TFTR which commenced in April of 1997. This paper describes in detail the configuration of these systems and the data obtained during the outage and decommissioning of TFTR.

*Work supported by U.S. DoE Contract No. DE-AC02-76-CHO3073.