Evaluation of dose due to ingestion of natural radionuclides of the uranium series in spring waters.

The concentrations of uranium isotopes and their decay products 226Ra, 222Rn, 210Pb and 210po have been analyzed in the mineral spring waters of a highly radioactive region of Brazil: Aguas da Prata. This region is located in the Poços de Caldas Plateau, one of the largest weathered alkaline intrusions in the world. Dose calculations were performed to evaluate the relative importance of these radionuclides in the exposure of the local population to radiation. Based upon concentrations measured in all the springs available, effective doses per year varying from 1.4 x 10(-4) mSv year(-1) for 238U to 5.1 x 10(-2) mSv year(-1) for 222Rn were observed. The doses from the ingestion of 222Rn, 210Po and 210Pb are of the same order of magnitude, and therefore these radionuclides are the most critical as far as the consumption of these waters is concerned.