TFTR D-T EXPERIENCE WITH TRITIUM RADIOACTIVITY DURING MAINTENANCE

The Tokamak Fusion Test Reactor (TFTR) facility began operations with trace tritium in July 1993. These operations consist of the delivery, storage, injection, and subsequent processing of tritium gas in suppor t of the D-T fusion program. The tritium is transferred throughout the facility using vacuum pumping systems and expansion volumes. These sy stems have manipulated and processed 14.4 PBq (388,983 Ci) of tritium from July 1993 through December 1994. This paper discusses the operati onal health physics program with regard to the performance of maintena nce on tritium contaminated systems. Data and findings are provided fr om maintenance situations ranging from work on small volume piping to large volume neutral beam systems. Results and comparisons of tritium contamination levels, airborne radioactivity levels, and oil concentra tions are presented for these systems. Descriptions of the maintenance tasks are provided for the entire scope of work and include general i nformation toward conceptual understanding of the maintenance conduct of operations. General procedural requirements, job planning, pre-job briefing topics, control mechanisms, techniques to reduce exposure, an d lessons learned are discussed. A complete description of various typ es of tritium monitoring and sampling equipment is also discussed. Sev eral types of air monitoring equipment were used during these tasks to identify the most consistent and reliable methods for detection and r adiological assessments. The results of radiological measurements are described in relation to the differentiation of elemental tritium to t ritium oxide in worker's breathing zones and the associated general wo rk area. A comparison is provided to process system monitoring, system moist air purges, system contamination levels and subsequent stack em ission sampling for both elemental and oxide tritium. A summary is pro vided to describe the relationship between elemental and oxide tritium as a result of properly planned and performed maintenance on tritium process systems.