Estimation of the Uranium Content of Geological Units in Eastern Senegal from Airborne and Ground Radiometric Data.

For several decades, uranium (U) has become the main element for the production of electricity in many countries. It is a good ally in the fight against global warming thanks to its low-polluting nature, as it does not emit greenhouse gases, its ability to provide enough energy to meet the growing demand of the world's population and its long-term availability compared to fossil fuels. In Africa, only South Africa has nuclear power plants. However, several other African countries (Nigeria, Egypt, Sudan) have nuclear ambitions. U deposits can be found in almost all types of rocks from Neoarchean to Quaternary dates [1]. The presence of U in significant concentrations also presents an exposure risk to populations. The objective of our study is to obtain a global view of uranium content and possible extreme concentrations within the geological units defined in the geological map of eastern Senegal at a scale of 1:200,000. This exploratory work is inspired by the methodology adopted by Ielsch (2017)[2] used to produce a global map of uranium in France. It consists of making an initial estimate of U content based on the interpretation of airborne radiometric data from eastern Senegal. The results show a good correlation between the statistical parameters of Th and U. Airborne radiometric surveys, which record gamma radiation emanating from the first few centimeters of soil, provide concentrations of radionuclides (K, Th, U) contained in soils and regoliths that are different from the concentrations in rocks a few meters below ground. We therefore used a portable radiometer spectro and carried out field measurements with the objective of understanding and describing, for each unit, the differences observed between ground and airborne measurements, in order to "correct" the airborne measurements to obtain a global view of Uranium in eastern Senegal. [1] M. Cuney, « The extreme diversity of uranium deposits », Miner Deposita, vol. 44, no 1, p. 3-9, janv. 2009, doi: 10.1007/s00126-008-0223-1. [2] G. Ielsch, M. Cuney, F. Buscail, F. Rossi, A. Leon, et M. E. Cushing, « Estimation and mapping of uranium content of geological units in France », Journal of Environmental Radioactivity, vol. 166, p. 210-219, janv. 2017, doi: 10.1016/j.jenvrad.2016.05.022.