Radiation exposure from radionuclides in ground water: an uncertainty analysis for selected exposure scenarios

The uncertainty of the potential radiation exposure of the general population has been estimated for a normalized contamination of ground water that is being used as drinking water for humans and animals, for irrigation of food and feed crops, and for fish production in freshwater bodies. The frequency distributions of annual effective dose equivalents were calculated assuming a normalized activity concentration in water of 1 Bq/l for each radionuclide considered. Estimated frequency distributions of the parameters were used as model input. This estimation is based on an exposure scenario which reflects the present radioecological conditions. Another important source for the uncertainty of the potential dose due to radionuclides released to the ground water is the uncertainty of the exposure scenario. Since such a contamination may not occur before some time in the far future, it is impossible to predict the exact boundary conditions. Therefore, scenarios were stimulated with modified consumption habits, more extensive farm management and different climatic conditions. The distributions of the potential doses cover in general about a factor of 10-20. The intake of drinking water, the root uptake and the contamination of fish are most important for the resulting potential radiation exposure. For nearly all radionuclides, the intake of drinking water dominates the potential exposure. In most cases radioactive daughter nuclides are of minor importance. In general, the influence of the exposure scenario on the dose is relatively small.