A Simulated Accidental Release and Dispersion of Gaseous Fission Products from NIRR-1: Implications for Emergency Response Planning

For over seven decades, research reactors have contributed significantly to the global economy, with uses in various fields such as food production, health and environment, industries, research and development, and education and training. The Nigerian Research Reactor-1 (NIRR-1) is vital in neutron activation analysis (NAA) and radioisotope production for education and training. The current NIRR-1 core uses Low Enriched Uranium (LEU) fuel, converted from Highly Enriched Uranium (HEU) fuel. The LEU core achieved its first criticality in December 2018 and has been safely operating at full and half power. This study uses the Hot Spot computer code to examine the dispersion of radionuclides accidentally released from the NIRR-1 LEU core during the final stage of its lifetime. Site-specific meteorological conditions were used to analyze the behavior and movement of selected gaseous radionuclides in the atmosphere. The total maximum respirable time-integrated concentrations of the released gaseous radionuclides in air were estimated at varying distances from the exposed reactor core, and the values obtained were , , , and at 10 m, 100 m, 300 m, and 1 km, respectively. These results highlight a possible risk within 300 m perimeter downwind for unclassified personnel, which is therefore crucial in developing comprehensive emergency preparedness and response plans.