Radon exhalation and gamma radioactivity levels in soil and radiation hazard assessment in the surrounding area of National Thermal Power Corporation, Dadri (U.P.), India

Abstract

In the present study soil samples were collected from the region around a National Thermal Power Corporation (NTPC) at Dadri (U.P.), India. Radon activity and radon exhalation rates were measured by using “sealed can technique” using LR 115-type II nuclear track detectors. Radon activities are found to vary from 177.5 ± 23.1 to 583.4 ± 4.9 Bq m−3 with an average value of 330.5 ± 30.4 Bq m−3. Surface exhalation rates in these samples vary from 63.9 ± 8.3 to 210.2 ± 15.1 mBq m−2 h−1 with an average value of 119.1 ± 11.1 mBq m−2 h−1, whereas mass exhalation rates vary from 2.5 ± 0.3 to 8.1 ± 0.6 mBq kg−1 h−1 with an average of 4.6 ± 0.4 mBq kg−1 h−1. Activity concentrations of naturally occurring radionuclides (226Ra, 232Th and 40K) were also measured in these soil samples using high resolution γ–ray spectroscopic system. Activity concentrations of 226Ra, 232Th, and 40K vary from 32.2 ± 6.0 to120.9 ± 4.5 Bq kg−1, 19.3 ± 0.9 to 44.6 ± 1.5 Bq kg−1 and 195.4 ± 2.8 to 505.4 ± 6.3 Bq kg−1 with overall mean values of 70.0 ± 8.9 Bq kg−1, 34.8 ± 1.2 Bq kg−1 and 436.1 ± 5.6 Bq kg−1 respectively. From the activity concentrations of 226Ra, 232Th and 40K, radium equivalent activity (Raeq) and the external hazard index (Hex) were calculated and found to vary from 73.4 to 214.7 Bq kg−1 and from 0.2 to 0.6 respectively.