Modelling Radioactive Contamination Dispersion from a Hypothetical Nuclear Facility Incident in Nigeria

Emergency preparedness for radiological incidents requires site-specific atmospheric dispersion modelling to estimate the spatial extent of radioactive contamination and inform evacuation and sheltering decisions. Nigeria's expanding interest in nuclear power as part of its energy mix makes emergency planning modelling increasingly relevant. This study models the atmospheric dispersion of radioactive contamination from a hypothetical source term release scenario at a proposed nuclear facility site in Nigeria's North Central region. The Gaussian plume and puff dispersion models are applied using meteorological data from the nearest first-order meteorological station for both pasquill-Gifford stability class conditions representative of harmattan and rainy season weather. Radionuclides modelled include Cs-137, I-131, and Sr-90 with source terms based on scaled reference accident scenarios from IAEA Safety Reports Series. Deposition, resuspension, and ingestion pathway doses are computed for 5, 10, 20, and 50 km receptor distances. Results indicate that worst-case stable atmospheric conditions with low wind speed produce ground-level air concentrations approximately 4 times higher than neutral stability conditions at 10 km. The modelled protective action zones correspond to 3 km for sheltering and 8 km for precautionary evacuation under conservative assumptions. Keywords: atmospheric dispersion, radioactive contamination, nuclear emergency, Nigeria, Gaussian plume