ABSORBED DOSE RATES ABOVE SOILS AND ROCK OUTCROPS IN SELECTED AREAS OF ABEOKUTA, NIGERIA
Outdoor absorbed dose rates were measured in selected areas of Abeokuta in Nigeria; some with rock outcrops and others with soil overburden. Measurements were carried out using a Geiger Muller Survey Meter and a Global Positioning System (GPS). Result shows absorbed dose rates ranged from 1.0 x 103 to 1.3 x 103 nGy/hr among the rock outcrop areas and from 0.6 x 103 to 0.8 x 103 nGy/hr among the soil -covered areas. The average absorbed dose rate was 1180 ±3 nGy/hr for the rock outcrop areas and 689 ±3 nGy/hr for the soil -covered areas and assuming 0.4 occupancy factor, the corresponding average annual effective dose rates were calculated to be 2.89 ± 0.01 mSv/yr for the rock outcrop areas and 1.69 ± 0.01 mSv/yr for the soil –covered areas based on occupancy factor of 0.4. The mean annual effective dose rates for both the rock outcrop and soil covered areas were found to be higher than 1mSv/yr, the recommended dose limit for the public.
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