Effect of non-spherical morphology on aerosol evolution in reactor containment using size-dependent dynamic shape factors

Abstract

The aerodynamic behavior of aerosol particles is significantly influenced by their size distribution and morphology. Conventional aerosol dynamics models often assume spherical, fully dense particles, which can lead to inaccuracies in predicting aerosol transport and deposition. This study highlights the necessity of incorporating dynamic shape factors to account for the non-sphericity of aerosol aggregates across different momentum transfer regimes. Using a geometric descriptors-based approach (GDA), we derive empirical relations for size-dependent dynamic shape factors, covering the entire Knudsen number range. These relations provide precise inputs for aerosol dynamics codes, enhancing the accuracy of nuclear accident simulations.

Application of these relationships to a pressurized heavy water reactor (PHWR) containment environment demonstrates that assuming spherical morphology underestimates airborne aerosol concentrations, particularly for aggregates with lower fractal dimensions. The study reveals that fractal aggregates experience increased drag forces, leading to significantly slower mass concentration reduction—approximately 25 times slower than that of spherical particles in a typical release scenario. By integrating these empirical expressions into aerosol modeling frameworks, this work improves predictions of aerosol transport, deposition, and airborne concentrations, thereby refining radiological safety assessments. The findings have direct implications for source term estimation, emergency response planning, and inhalation toxicology studies, reinforcing the critical role of dynamic shape factors in aerosol modeling.