A Comprehensive Study of Aerosol Transport and Deposition Behavior in Severe Reactor Accidents: Experimental and Modeling Approaches

Abstract

Radioactive aerosols may escape into the environment as the outcome of core meltdowns caused by severe accidents. The transport and deposition of these aerosols during such events can have significant and wide-ranging consequences. This study intends to advance the core damage assessment technology, with a particular focus on Level 2 probabilistic safety assessment, by providing a source term migration evaluation method using narrow circular channels. To achieve this, an experimental setup has been established that represents the leak paths via containment vessel penetrations and reactor buildings, as well as the environmental and flow conditions during severe accidents. Experiments were carried out to investigate the effects of flow Reynolds number, aerosol particle size, and leakage path diameter and length on the decontamination factors (DFs). In addition to experimental endeavors, a theoretical model has been developed to investigate the deposition and transport of accidental source terms, considering the re-entrainment effect. Both the particle concentration and the deposited particle numbers on the surface are considered position and time dependent in the model, so it can predict the transient DFs along with the average DFs that are obtained from the experiment. The model results are compared and validated with the experimentally obtained DFs. These experimental and theoretical results reveal that DF increases with flow path length and Reynolds number while decreasing with flow path diameter and particle mass median diameter at higher Reynolds number ranges.