Dose-rate conversion factors for external exposure to photons and electrons.

Dose-rate conversion factors for external exposure to photons and electrons have been calculated for approx. 500 radionuclides of potential importance in environmental radiological assessments. The three exposure modes considered are immersion in contaminated air, immersion in contaminated water, and irradiation at a height of 1 m above a contaminated ground surface. For each exposure mode, the source region is assumed to be effectively semi-infinite or infinite in extent with uniform radionuclide concentration. The dose-rate factors then give external dose-equivalent rates per unit radionuclide concentration in air, in water or on the ground surface. The results are tabulated in this paper in the form of effective dose-rate factors based on the definition of the effective dose equivalent given in ICRP Publication 26 (ICRP77). The effective dose-rate factors are obtained from photon dose-rate factors for 23 separate body organs and electron dose-rate factors for skin calculated with the revised DOSFACTER computer code (Ko81a). In addition to presenting the dose-rate factor equations and the tabulated results, this paper emphasizes the assumptions underlying the calculations for each exposure mode, differences between the organ dose-rate factors for photons used here and those used previously with the original version of the DOSFACTER code (Ko80a), and limitations inherent in application of the idealized external dose-rate factors to realistic environmental radiological assessments.