Terrestrial Radiation Doses from Selected Towns of Southwestern Nigeria

OJO Taiwo John^1, and GBADEGESIN Karonwi A. Joseph¹

¹Physics Unit, Department of Science Technology, The Federal Polytechnic, Ado-Ekiti Nigeria

Cite this paper:
OJO Taiwo John and GBADEGESIN Karonwi A. Joseph. Terrestrial Radiation Doses from Selected Towns of Southwestern Nigeria. International Journal of Physics. 2015; 3(6):244-247. doi: 10.12691/ijp-3-6-4

Abstract

The activity concentrations of natural gamma-emitting radionuclides ²³⁸U, ²³²Th and ⁴⁰K in soils from 7 sampling sites each in Ondo and Lagos States, southwestern Nigeria have been measured by using a well calibrated Hyper Pure Germanium Detector (HPGe). 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 for . Activity concentration values of 23.21±0.92, 22.84 ± 0.78 and 204.02±7.00 Bq kg^-1 were recorded for ²³⁸U, ²³²Th and ⁴⁰K respectively for . The results obtained were used to estimate the absorbed dose rates in outdoor air which was found to be in the range of 12.35±179.59 nGy h^-1 for Ondo State and 5.91±83.29 nGy h^-1 for Lagos State with an overall mean values of 67.50±1.86 nGy h^-1 and 33.83±1.17 nGy h^-1 respectively for the two States. The corresponding outdoor annual effective dose rates were estimated to be between 22.7 and 330.6 μSv y^-1 for and between 7.3 and 102.2 μSv y^-1 for assuming 30% and 20% occupancy factors for the two states respectively. The average outdoor annual effective dose rate for towns in Ondo State is 64.85 μSv y^-1 representing 92.64% of the world average value (70 μSv y^-1) given by UNSCEAR. However, the cities in have an average outdoor effective dose of 41.52 μSv y^-1 which is less than 60% of the world average value. The values of the collective effective dose as calculated from the outdoor annual effective dose rates were found to be 540858 and 273296 person-Sv for Ondo and Lagos States respectively.

Keywords:
radionuclide activity concentration outdoor effective dose absorbed dose

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