Assessment of radiological hazards and effective dose from natural radioactivity in rock samples of Hassan district, Karnataka, India

The natural primordial radionuclide activity concentrations in different types of rock samples in and around Hassan district were measured using gamma spectrometry-based high-purity Germanium detector. The average activity concentration of Ra-226, Th-232, and K-40 radionuclides in rock samples varies from 29.4 +/- 1.2 to 83.7 +/- 1.7, 37.9 +/- 1.2 to 198.4 +/- 2.2, and 346.1 +/- 9.0 to 1024.4 +/- 19.4 Bq kg(-1) with an average value of 50.9 +/- 1.4, 79.6 +/- 1.5, and 609.2 +/- 12.8 Bq kg(-1), respectively. The radiological hazard indices such as radium equivalent activity, gamma index, alpha index, external and internal health hazard indices, absorbed dose rate and annual effective doses were estimated. The average value of radium equivalent activity is less than the criterion limit of 370 Bq kg(-1). The average indoor and outdoor annual effective dose values for rock samples are lower than the world average recommended value of 1 mSv y(-1). The study concludes that except granite rocks, all the rock samples analyzed are safe when used as construction materials and do not pose any significant radiation hazards.