Study on the diffusion of UF6 leakage and the evolution of UO2F2 particles using the PBM model for multiphase flows based on OpenFOAM

Uranium hexafluoride (UF 6 ) released into air undergoes rapid cooling and reacts with water vapor to generate highly toxic HF gas and solid UO 2 F 2 aerosol particles. In this work, the formation and growth of UO 2 F 2 particles are described using a population balance model (PBM). A coupled multiphysics framework is developed on the OpenFOAM platform by integrating large eddy simulation (LES), multicomponent gas transport, UF 6 phase-change source terms (mass/energy), global hydrolysis kinetics, and PBM-based particle evolution. The model is applied to simulate UF 6 leakage from a pipeline into an enclosed room. The results indicate that UF 6 exhibits pronounced heavy-gas behavior after release, while phase-change and hydrolysis source terms jointly affect the temperature field and species distributions. Increasing leakage rate enlarges the UF 6 affected region and significantly enhances UO 2 F 2 particle formation and turbulent coalescence, leading to larger mean particle diameters and altered particle transport and deposition patterns. The findings provide quantitative support for consequence assessment and mitigation strategies for UF 6 leakage accidents.