Natural Radioactivity, Radon Exhalation Rates and Radiation Doses in the Soil Samples Collected from the Vicinity of Kolaghat Thermal Power Plant, West Bengal, India

Natural radioactivity has been determined by means of a highly efficient thallium-doped sodium iodide detector in soil sample from surface of from vicinage of “Kolaghat Thermal Power Plant” The activity concentration (specific activity) is found to vary from 23.70 ± 3.41 to 33.90 ± 4.33 Bqkg^-1 for ²²⁶Ra, from 6.67 ± 2.01 to 21.60 ± 2.11 Bqkg^-1 for ²³²Th and that for ⁴⁰K from 461.01 ± 66.16 to 610.25 ± 80.87 Bqkg^-1 with expected value of 29.26 ± 3.50, 4.86 ± 2.03 and 517.53 ± 71.61 Bqkg^-1 of Radium-226, Thorium-232 and Potassium-40 correspondingly. The radon exhalation rates were also computed from all samples using the "Sealed Can Technique”. The activity due to radon fluctuates from 47.9 ± 6.2 to 157.6 ± 11.3 Bqm^-3 having an arithmetic mean of 89.3 ± 7.9 Bqm^-3. The surface exhalation rate and mass exhalation rates were estimated to fluctuate from 17.3 ± 2.2 to 56.8 ± 4.1 mBqm^-2h^-1 with an expectation of 32.1 ±\± 3.0 mBqm^-2h^-1 and from 0.6 ± 0.1 to 2.1 ± 0.2 mBqkg^-1h^-1 averaged out to 1.2 ± 0.1 mBqkg^-1h^-1 respectively. Radiation doses were also calculated in these samples. Indoor and outdoor annual effective doses, Absorbed dose rates, External Hazard index and Indoor inhalation exposure, also known as radon effective dose, was computed and varied from 0.19 to 0.25 mSv y^-1, 39.30 to 51.61 nGyh^-1, 0.048 to 0.063 mSvy^-1, 0.21 to 0.28 and 0.29 to 0.36 and 2.04 to 6.70 μSvy^-1 respectively. The values which were obtained in this study are found to be well below the allowed permissible limits, so the soil may be used as building construction material.