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External Radiation Exposure

The nature and extent of the radiation hazard differed considerably among facilities and over time. A detailed description of the monitoring programs for external and internal radiation at each facility, and results summarizing the exposure characteristics by race and gender are given by Watkins et al in [2,3]. Annual external dose estimates were obtained for each monitored worker at each Oak Ridge facility. Evaluation of these results [2,3] showed that over 93 percent of the total recorded external dose was received by the 28,770 white males who had ever been employed at the X-10 or Y-12 sites, and that about 30 percent of these workers were employed at more than one Oak Ridge facility. Results from the facility comparison analyses (see Results) show that most of the workers at K-25 and TEC had higher death rates than those at X-10 and Y-12, so inclusion of K-25 and TEC workers would potentially lead to overestimation of baseline mortality rates and underestimation of radiation effects. For these reasons the dose-response analyses for external radiation were restricted to white males who were ever employed at X-10 or Y-12. The other race/gender groups at these facilities were not included since they would contribute little to the assessment of effects of low-level radiation and would unduly complicate the dose-response analyses.

To provide a preliminary evaluation of the potential effect of ``missing dose'' on radiation dose-response estimates the doses for X-10 workers prior to 1957 and for Y-12 workers prior to 1961 were adjusted. The adjustment procedure increased dose estimates for some person-years under assumptions about the minimum detectable dose and the monitoring policies that were followed at X-10 and Y-12. Other sources of systematic and random measurement error are not addressed by this procedure. A detailed discussion of how these crude adjustments were made and summary results are provided by Watkins et al [2,5,3].


Figure 4 from Watkins et al
Types of Dosimeters and Frequency of Readings for Oak Ridge Workers by Plant, 1943-1984



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Next: Internal Radiation Exposure Up: Definition of Study Previous: Definition of Study