Dose assessment studies at former nuclear weapons test sites in Australia

Field and laboratory measurements are described and data presented which enable a dose assessment for the inhalation of artificial radionuclides at Maralinga and Emu, the sites of United kingdom atomic weapons tests between 1953 and 1963. Dose assessments for the inhalation of artificial radionuclides are presented for all remaining contaminated areas at Maralinga and Emu. In the case of Aborigines, these doses are estimated assuming inhalable dust loadings of 1 mg/m3 for adults and 1.5 mg/m3 for children and infants. Particle size is taken to be 5 μm AMAD. Plutonium and americium are taken to be represented by solubility Class Y for major trial sites and 25% Class W and 75% Class Y for all minor trial sites. For other radionuclides, where no data are available, the most conservative dose intake conversion factor values are used. All calculations of dose assume 100% occupancy. The results indicate that doses to children are higher than doses to adults and infants. This is a consequence of children being subjected to higher dust concentrations than adults because of their play activities and because of generally higher dose intake conversion factor values than adults, which more than offset their smaller breathing rates. Thus children form the critical group. With the exception of one site which is contaminated with uranium, at all other sites it is only the inhalation of plutonium and americium that contributes significantly to the dose, and of these 239Pu is the largest contributor. Therefore, having regard to the long half lives of the radionuclides concerned, the inhalation problems highlighted by this dose assessment will not diminish significantly within any reasonable period of time and hence management strategies must be developed to deal with them. (author). 35 refs, 1 fig., 2 tabs