Study of distribution of 226Ra, 232Th and 4°K in different rock formations and their dose estimation in and around Chickmagalur, India

Background: The concentrations of radionuclides like Ra, Th and K and the dose rate are measured in igneous and metamorphic rock formations in and around Chickmagalur. A total of 236 samples from 13 different locations around study area were analyzed. Materials and Methods: The activity concentrations of the three radioactive elements were determined for mean period of 25000 s using HPGe (GMX - 10190) detector and the dose calculations were made using standard formulae. Results: The mean activity concentrations in igneous rocks recorded were 36.6 Bqkg, 73.2 Bqkg-1 and 992.3 Bqkg-1 for 226Ra, 232Th and 40K respectively. The mean activity concentrations in metamorphic rocks were 17.2 Bqkg-1, 28.1 Bqkg-1 and 617.8 Bqkg-1 for 226Ra, 232Th and 40K respectively. Assuming 20% occupancy factor, the corresponding mean annual effective dose due to igneous and metamorphic rocks were 169.6 ^Sv and 90 ^Sv respectively. Conclusion: The concentrations of radionuclides were found to be in similar with global and Indian average ( 1 - 3 ) .