Tissue to air ratios for open-cut uranium mine employees: a simulation using circular plane sources

Tissue to air ratios of absorbed dose have been measured for certain organs in an Alderson Rando radiotherapy phantom irradiated by simulated circular plane sources of degraded gamma rays from radium-226. The absorbed dose measurements were performed using thermoluminescent dosemeters. Factors were determined which relate the absorbed dose received by the organ, of interest to (i) the absorbed dose in air at the height of the organ, (ii) the absorbed dose measured by a personal monitor worn at the chest and waist, and (iii) the absorbed dose in air at 1 m above the source. Effective dose equivalents have been calculated using the above factors in conjunction with ICRP 26 weighting factors. The results indicate that a good estimate of the effective dose equivalent can be obtained irrespective of the wearing position of the personal monitor on the trunk.