Determination of Uranium in Rocks and Soils of South Cameroon by γ-ray Spectrometry

Abstract

Analytical results of uranium concentration in rocks and soils collected in the area of Lolodorf of South Cameroon where a radiometric anomaly had been found by previous investigation are reported. The analysis has been carried out by γ-ray spectrometry using a Ge detector. Radioactivity concentration of ²³⁵U was determined by comparing peak count rates of samples with those of natural uranium standard sample. Radioactivity concentration of ²³⁸U was calculated from the ²³⁵U radioactivity concentration by assuming that the isotopic composition of ²³⁵U is 0.7200% of natural abundance. Difference of γ-ray self-absorption between the samples and uranium standard was accurately corrected by using a mass attenuation coefficient of samples and standard measured by using an external γ-ray source. The radioactivity concentrations in rocks ranged from 0.92±0.02 to 228±14Bq/kg(²³⁵U) and 20±5 to 4868±307Bq/kg(²³⁸U), while radioactivity concentrations in soils ranged from 3±1 to 63±2 Bq/kg(²³⁵U) and 71±19 to 1346±38 Bq/kg(²³⁸U). The γ-ray dose rates in air at 1m above the ground surface due to the high uranium concentration in soil samples were ranged from 33±9 to 622±18 nGy/h. The highest uranium concentration of about 0.04% in rock was found in the analysis. These results show that the uranium content in the studied areas is significantly high and the studied areas have a potential for uranium mining.