Natural Radionuclide Concentration in Kaolin Deposits and Dose Assessment Within Delta State, Nigeria

Abstract

The assessment of natural radionuclide concentration in kaolin deposits and dose rate within Delta state, Nigeria has been carried out. Four kaolin mining sites within four Local Government Areas in the state were studied. Background Ionizing Radiation levels of each of the mining site was measured using a Gamma Scout handheld radiation meter and a GPS meter used to obtain the actual positions where the BIR levels were taken around each kaolin site. A total of twenty-five (25) samples were collected for Gamma spectrometry analysis at National Institute of Radiation Protection and Research, University of Ibadan. The mean BIR exposure rates for Ukwuani, Aniocha South, Ughelli North and Ughelli South LGAs were 0.01mRh -1 , 0.013mRh -1 , 0.013mRh -1 and 0.014mRh -1 respectively and were within the world’s recommended permissible limit of 0.013mRh -1 given by UNSCEAR. The mean activity concentrations of 238 U, 232 Th and 40 K in kaolin samples were estimated to be 137.028 ± 7.194, 13.532 ± 1.568 and 6.724 ± 0.396 Bqkg -1 respectively for Ukwuani; 425.494 ± 22.16, 18.63 ± 2.17 and 11.955 ± 0.71 Bqkg -1 respectively for Ughelli South; 596 ± 30.772, 18.728 ± 2.124 and 8.912 ± 0.526 Bqkg -1 respectively for Ughelli North and finally, 120.026 ± 6.235, 10.533 ± 1.182 and 15.024 ± 0.879 Bqkg -1 respectively for Aniocha South. These results compare quite well with the world’s average value of activity concentrations for natural radionuclides reported by UNSCEAR, except for 40 K which is higher than the world’s average at Ughelli North and South. The values of all the radiological hazard parameters for all the mining sites are less than the recommended limits. The calculated Excess Lifetime Cancer Risk also reveal that the values are all within the recommended limits, therefore, the risk of cancer inducement due to radiation exposure is within the acceptable limits for all the mining sites.