Study of radon exhalation rate and natural radioactivity in soil samples collected from East Singhbhum Shear Zone in Jaduguda U-Mines Area, Jharkhand, India and its radiological implications

摘要

In the present study, Sealed Can Technique was adopted for radon exhalation measurements in soil samples collected from some areas around the East Singhbhum shear zone in U-mining area of Jharkhand state of India. Radon activity varies from 3794.3 to 4891.4 Bqm~(-3) with an average value of 4368.6 Bqm~(-3) while radon exhalation rate varies from 1364.1 to 1758.6 mBqm~(-2)h~(-1) with an average value of 1573.8 mBqm~(-2)h~(-1). Activity concentrations of naturally occurring radionuclides (~(238)U, ~(232)Th and ~(40)K) were also measured in these soil samples using high resolution -ray spectroscopic system. Activity concentrations were found to vary from 6.1 ± 0.2 to 826.3 ± 8.5 Bq kg~(-1) for ~(238)U, 8.7 ± 0.3 to 236.7 ± 3.2 Bq kg~(-1) for ~(232)Th and 291.5 ± 4.4 to 1391 ± 14.3 Bq kg~(-1) for ~(40)K. From the activity concentration of ~(238)U, ~(232)Th and ~(40)K in these soil samples, the radium equivalent activity (Ra_(eq)) due to the presence of radionuclides is calculated and it varies from 34.0 to 924.5 Bq kg~(-1) with an average value of 260.4 Bq kg~(-1). Total absorbed gamma dose rates in the surrounding air are found to vary from 15.1 to 402.0 nGyh~(-1) with an average value of 120.8 nGyh~(-1). The indoor and outdoor annual effective dose rates from these soil samples are determined from 0.1 to 1.9 mSv y~(-1) and 0.03 to 0.8 mSv y~(-1), respectively. External hazard index, H_(ex) for the soil samples studied in this work ranges from 0.14 to 2.46 with a mean value of 0.70. The internal exposure to ~(222)Rn and its radioactive progeny are controlled by the internal hazard index Hin. Computed values of Hin vary from 0.2 to 4.8 with an average value of 1.02.