Natural radioactivity in rock samples of Aravali hills in India

Natural radionuclides in rock samples, primarily 238U (uranium), 232Th (thorium) and 40K (potassium), are the main source of radiation exposure to workers and general public and their measurement is of paramount importance from radiation protection point of view.
Gamma spectrometry using HPGe detector was used to measure the radioactivity and assess the radiological hazards and annual effective dose. The data is statistically significant.
In the studied rock samples, the mean activity of 238U, 232Th, 40K is 12.15 ± 1.68 Bq/kg, 45.17 ± 6.92 Bq/kg and 639.24 ± 115.86 Bq/kg, respectively. The mean values of radium equivalent activity, radiological hazards external hazard index (Hex), Internal hazard index (Hin), Gamma index (Iγ) and Alpha index (Iα) are 125.96 ± 14.94 Bq/kg, 0.34 ± 0.04, 0.37 ± 0.04, 0.48 ± 0.06 and 0.06 ± 0.00 respectively. The mean values of absorbed dose rate, indoor and outdoor annual effective dose of gamma radiation are 59.55 ± 7.16 nGy/h, 0.29 ± 0.04 mSv and 0.07 ± 0.00 respectively. A strong positive correlation was observed between the radium equivalent activity and the absorbed dose (correlation coefficient R2 = 0.99).
The present investigations showed that the inborn radioactivity is within the world and Indian average value. And the findings indicate that the studied samples do not pose any significant radiation hazard to the public in large and the workers in particular and when used as construction material also.