Studies on natural radioactivity in rocks of Coorg district, Karnataka state, India

The paper deals with the study of natural radioactivity in the rocks of Coorg district, Karnataka state. The samples were analyzed by NaI(Tl) based gamma ray spectrometer. The activity of 232Th varies from 16.46 Bq kg−1 to 160.84 Bq kg−1 with mean value of 79.05 Bq kg−1. The activity of 40K varies from 96.72 Bq kg−1 to 933.68 Bq kg−1 and that of 226Ra was found to vary from BDL to 34.36 Bq kg−1. A correlation coefficient of R = 0.81 was found between 232Th activity and 40K activity. The correlation between 226Ra activity and 232Th activity is R = 0.59. The correlation between 40K and 226Ra is R = 0.51. The Radium Equivalent Activity (Raeq) ranges from 46.78Bq kg−1 to 315.55Bq kg−1. The absorbed gamma dose rate (D) ranges from 21.28 nGy h−1 to 141.45 nGy h−1, with an average of 73.37 nGy h−1. The radionuclides activity was compared with world average values. The external Hazard index (Hex) varies from 0.12 to 0.84. The internal hazard index (Hin) is in the range 0.15-0.89. The hazard indices were found to be within safety limits.