Measurement of Radiation Exposure Due to Natural Radionuclides in Gemstone Mining Area in Olode, Ibadan South Western Nigeria

Aims: To determine the level of radioactivity due to naturally occurring radioactive materials (NORM) and also assess the radiological hazards to both workers and the public.
Place and Duration of Study: Centre for Energy Research and Development, Obafemi Awolowo University, Ile-Ife, Nigeria between January and April 2012.
Methodology: Fifteen samples comprising rocks, soils, water and mine wastes were obtained from three (3) mining sites in Olode, Ibadan and a topsoil sample two kilometers away from the site that served as control were investigated for their natural radioactivity contents using a well-calibrated HPGe gamma-ray spectrometer.
Results: For both rock and soil samples, the activity concentrations of the radionuclides range between 86.42-2200.71Bq/kg; 3.00-13.11Bq/kg and 6.09-11.95Bq/kg for 40K, 238U and 232Th respectively, while the Absorbed Dose Rate and the Dose Equivalent were in the range of 10.58–96.71nGy/h and 0.07–0.6mSv/yr. In water, the activity concentration was in the order of 10-2 Bq/L and the Annual Effective Dose was between 0.08–0.12; 3.47–3.78 and 20.65–24.18μSv/yr for 40K, 238U and 232Th respectively.
Conclusion: The gemstone-bearing pegmatite rock from mine 1 has the highest dose equivalent value of 0.60mSv/yr which is lower than the threshold limit of 1mSv/yr set by the International Commission on Radiation Protection (ICRP) for the general public. The results obtained thus indicate that the mining activities do not pose any significant radiation hazard so far. However, caution must be exercised in case of prolonged exposure in the mine environment to avoid other unnecessary health hazards.