Assessment of Radiation Impact During an Accident at a Spent Nuclear Fuel Storage Facility

The study addresses the assessment and management of environmental safety at spent nuclear fuel (SNF) storage facilities under emergency conditions. The research aims to improve environmental safety management by integrating modern risk assessment approaches, external threat analysis, and advanced modeling tools. The focus is on understanding the processes of radiation formation, propagation, and deposition during accidents at SNF storage facilities, as well as on developing methods for evaluating contamination levels and the dispersion of radionuclides in the surrounding environment. A detailed sequence of procedures for radiation impact assessment is proposed, beginning with the collection of comprehensive data on the emission source, including radionuclide composition, activity levels, release height,speed, and direction. Meteorological data such as wind speed and direction, temperature, humidity, and atmospheric stability are incorporated, alongside topographic characteristics, which together determine the spatial and temporal spread of radioactive contamination. Diffusion models, particularly the Gaussian model, are employed to predict concentrations of radioactive admixtures, evaluate horizontal and vertical distributions in the atmosphere, describe dry deposition of particles, and estimate soil contamination. Mathematical relationships are presented for calculating radionuclide concentrations, dispersion coefficients, surface contamination density, and radiation doses to both personnel and the general population. The study also critically analyzes the limitations of the Gaussian model, including its assumptions of atmospheric homogeneity, simplified treatment of deposition processes, and lack of corrections for complex terrain, urban structures, convective flows, and variable turbulence. To address these limitations, complementary approaches, such as Lagrangian particle models and computational fluid dynamics (CFD) simulations, are discussed to provide more accurate predictions under heterogeneous and dynamic conditions. Emphasis is placed on integrating these methods with statistical analysis of particle size distributions, deposition rates, and emission scenarios to enhance reliability and applicability in real-world conditions. Based on the modeling results, a comprehensive framework for radiation risk assessment is developed, enabling the calculation of external and internal exposure through integral formulas and the estimation of the probability of adverse health effects. The proposed methodology allows for quantitative evaluation of risks that exceed permissible exposure levels and supports timely decision-making regarding protective measures. The findings can be applied to enhance environmental monitoring systems, improve the accuracy of predicting radioactive impact zones, and optimize the management of SNF storage facilities during emergency scenarios, ultimately contributing to increased environmental and public safety, as well as the development of guidelines for emergency preparedness and response.