Assessment of radiological safety of abandoned tantalite mining sites in Oke-Ogun, Oyo State, Nigeria

摘要

Introduction: Tantalite and other solid mineral deposits in Oke-Ogun occupy a very large landscape, and the possibilities of further exploration in new landscape and abandoning unproductive sites cannot be ruled out. These landscapes when abandoned become hideout for criminals and ritualistic activities which pose a great threat to the wellness of the people in the area and Nigerians at large. Objectives: This study attempts to investigate the radiological safety of these abandoned mines so as to convert them to economical valuable sites that can serve as a means of employment for population of the unemployed youth in the area and Nigeria at large. Materials and Methods: A total of seventeen soil samples were randomly selected. These samples were processed and analyzed for activity concentrations of ~(226)Ra, ~(232)Th, and ~(40)K using Hyper Pure Germanium Gamma Spectrometer. RESidual RADioactivity software version (6.5), a computer program developed by the Environmental Assessment Division of Argonne National Laboratory, was used for dose prediction for 70 years using the activity concentrations of soil samples from all the selected sites as its input parameter for the software. Predicted doses were estimated with respect to the three exposure pathways, namely external gamma irradiation from radionuclides in the soil samples, inhalation of dust particles, and inadvertent ingestion of soil. Results: The measured activity concentrations of radionuclides: ~(226)Ra for all the sites is in the range of (17-177) Bq/kg, ~(232)Th in the range of (2-107) Bq/kg, and ~(40)K in the range of (650-1667) Bq/kg. The predicted dose for all the sites is within the range of 0.05-0.35 mSv/y with Eluku mining site having values greater than the permissible limit of 0.25 mSv/y. The health implication of these values is that three of the sites (Gbedu, Sepenteri, and Komu) are safe for other usages. Conclusion: Any of these three mining sites may be used for re-creational purposes, fishing and building of estates to mention but a few.