Natural radionuclides in Niger delta sedimentary organic rock samples

Thirty sedimentary organic rock samples were collected at different depths from three oil wells in the Niger Delta. The natural radionuclides in the samples were measured in order to determine their geochemical significance and radiological effect. The radionuclides were measured using gamma spectrometric technique. Natural occurring radionuclides identified were uranium, thorium and potassium. The average activity concentrations obtained were 2441.65±753.00, 28.31±8.83 and 14.49±4.46 Bq/kg for 40K, 232Th and 238U, respectively. The equivalent doses calculated from activity concentrations of the radionuclides ranged from 0.69–1.25, 0.89–1.18, and 1.19–1.38 mSv/year for Meji, Malu and Mefa oil wells, respectively. These values are slightly higher than the normal background radiation value of 1 mSv/year. The background radiation of 40K detected in these samples was high, the absorbed dose rate and equivalent dose was slightly high, which could pose intrinsically radiological health hazard because of their cumulative radiological effect in the environment.