TFTR occupational radiation exposure data collection and analysis

Abstract Occupational radiation exposure (ORE) experience from existing fusion facilities represents a valuable source of information to assist in the development of ORE estimates for future fusion machines and possibly, in validating them. Accordingly, the worker dose experience from TFTR was of particular interest, not only because of the machine size, but also because of its D/T operation and because it saw the complete cycle of the plant life, including the decommissioning phase. The TFTR ORE experience was reviewed using a systematic approach similar to that used for JET. The worker dose data was reviewed on the basis of available documentation with the aim of identifying trends and relationships that would be useful for future fusion machine ORE estimates. The analysis has yielded some useful results and findings. The first finding is that the machine was shutdown, on an average, about 60% of the year. The second finding is that the ratio of exposed workers to monitored workers was about one-fifth. The third finding is that although, the major portion of worker dose was accrued by maintenance workers during shutdown periods, a significant portion (up to 20%) could have been accrued by non-maintenance work groups during operating periods (excluding plasma operation). Finally, after several years of machine operation with D/T plasmas, there is sufficient information to indicate that tritium doses did not contribute significantly to the total worker dose.