RESUMEN
Natural radiation is constantly present in the environment and is emitted from a variety of natural and artificial sources. It affects human body and environment. The activity concentrations of [238]U, [232]Th and [40]K have been determined by Gamma ray spectrometer with an HPGe detector in sediments of Cauvery River, Tamilnadu, India. The absorbed dose rate, radium equivalent concentration, external [Hex] and internal [Hin] hazardous indices are calculated from criteria formula and compared with the international recommended limits. The radioactive heat production rate and activity concentration index are also calculated. The observed dose rate measurements from ERDM [Environmental Radiation Dosi Meter] at 1m above the ground level at each site of the both rivers are measured and correlated with calculated absorbed dose rate. From the various parameters and correlation between them, the Cauvery River does not pose a radiological hazard except the site no. 21, 22, 23, 30, 31 and 35