Radon exhalation potential and natural radioactivity in soil collected from the surrounding area of a thermal power plant

In the present study, radon (Rn-222), thoron (Rn-220) exhalation rates, and the specific activities of U-238,Th-232, and K-40 of 75 soil samples collected from the surrounding area of a National Thermal Capital Power Station (NTPC) Dadri, are measured by using a continuous activity monitor, and high-resolution gamma-ray spectroscopy. Objective of the study is to find out if there is any excess radioactivity in the soil due to long term accumulation of fly ash on soil surface by comparing with data from adjoining region reported in literature. Also, to demonstrate the applicability of a radon exhalation-based model to quickly estimate the indoor radon concentration contributed by these soil samples if used for construction of houses. The mean values of radon mass and thorn surface exhalation rates are 50 +/- 12 m Bq kg(-1) h(-1) and 6 +/- 2 kBqm(-2) h(-1), respectively. The mean values with one standard deviation of Ra-226, Th-232, and K-40 activities are 50 +/- 6 Bq kg(-1), 68 +/- 10 Bq kg(-1), and 650 +/- 82 Bq kg(-1), respectively. The average values of absorbed gamma dose rate and annual effective dose outdoors with one standard deviation for the adult population are found to be 91 +/- 9 nGyh(-1) and 0.11 +/- 0.01 mSv, respectively. The average value of the radon emanation factor is found to be 0.13 +/- 0.03. To the best of our knowledge, such kind of study has not been carried out in this region and is reported first time in this paper.