Atmospheric dispersion and dose assessment of key radionuclides from a hypothetical VVER-1000 accident

Abstract In this study, the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model was utilized to simulate the atmospheric dispersion of major radionuclides including elements of Iodine ( 131 I, 132 I, 133 I, 134 I, 135 I), Cesium ( 134 Cs, 137 Cs), Strontium-90 ( 90 Sr), and Plutonium-239( 239 Pu) following a hypothetical accident at the VVER-1000 reactor (28.82°N, 50.88°E). Meteorological datasets from February, April, August, and October 2023 were incorporated into the model, and the corresponding inhalation and external radiation doses were evaluated using standard dose conversion factors. The simulation results demonstrated that both dispersion behavior and dose magnitude are highly influenced by meteorological parameters and the inherent physical–chemical characteristics of each radionuclide. Among the analyzed elements, 134 Cs exhibited the widest dispersion range, over a 24 h exposure period, the maximum inhalation dose (9.24 Sv) from 134 Cs and the maximum external dose from 131 I (1.28 Sv) were recorded in February. Furthermore, the maximum external dose from 134 Cs (0.22 Sv) was observed in August, and the maximum external dose from 133 I (0.04 Sv) was recorded in April. Incorporating seasonal variability and radionuclide-specific behavior into radiological impact assessments is significant. The results provide a robust scientific foundation for enhancing nuclear safety strategies, developing effective early warning systems, and optimizing emergency response and evacuation planning around nuclear power facilities.