T. Ojo ¹, K. A. J. Gbadegesin ²

Affiliations
1 Physics Unit of Science Technology Department, Federal Polytechnic, P.M.B 5351, Ado-Ekiti, NG
2 Physics Unit of Science Technology Department, Federal Polytechnic, P.M.B 5351, Ado-Ekiti,, NG

Abstract

The activity concentrations have been measured by using a well calibrated high resolution gamma ray spectrometer of natural gamma-emitting radionuclides ²³⁸U, ²³²Th and ⁴⁰K in soils, taken from 7 sampling sites in Ondo State, southwestern Nigeria. The mean activity concentration values of 39.24±1.12, 52.86±1.40 and 445.02±12.24 Bq kg^-1 for ²³⁸U, ²³²Th and ⁴⁰K respectively were obtained from the atmosphere of the State. Absorbed dose rates in the range of 12.35±0.65 and 179.59±4.1 nGy h^-1 with an overall mean value of 67.50±1.86 nGy h^-1. The corresponding atmosphere annual effective dose rates were estimated to be between 22.7 and 330.6 μSv y^-1 for the area, assuming 30% occupancy factors. The average outdoor annual effective dose rate for most of the towns is 64882.95 μSv y^-1 representing 92.65% of the world average value (70000 μSv y^-1) given by UNSCEAR. The value of the collective effective dose as calculated from the atmospheric annual effective dose rates was found to be 540858 person-Sv .

Keywords

Radionuclide, Radiation, Gamma, Dose, Exposure

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