Radiological hazards assessment of laterite mining field in Ilorin, North-central Nigeria

Background: Assessment of activity concentrations of 238U, 232Th, 40K and gamma dose rate (DR) was carried out over a laterite mining field in Ilorin-south, Nigeria. Materials and Methods: A well calibrated Super-Spec (RS-125) gamma spectrometer was used to measure the activity concentrations of 40K, 238U, 232Th and gamma doses rate at 1 m above the ground level over the laterite mining field. Fifty (50) measurements of the activity concentration of the radionuclides were obtained at about 1 meter above the topsoil. For each point, measurements were taken four (4) times for better accuracy. Results: The overall mean of the activity concentrations of 40K, 238U and 232Th are 81.38, 43.89 and 38.79 Bqkg-1 respectively. The mean value for DR was found to be 46.44 nGyhr-1. The mean activity concentrations of 238U and 232Th are higher than the recommended limits provided by UNSCEAR. This is a cause for worry as significant enhancement in the concentration of 238U and 232Th will increase the level of the background radiation and possibly render the soil unfit for use in building and construction. The results of most of the radiological impact parameters (RIP) are above the limits provided by UNSCEAR. Conclusion: From the results, it implies that the risk of indoor gamma radiation exposure is high for this lateritic soil. So the lateritic soil from this mine field may not be too suitable for building and construction purposes.