Investigations on aerosol transport and deposition behavior during severe reactor accident

Abstract

The accident at the Fukushima Daiichi Nuclear Power Plant in 2011 led to a core meltdown, resulting in the significant release of radioactive materials into the environment, revealing the urgent need for further in-depth development of Level 2 probabilistic safety assessment technology. To help establish an effective source-term migration evaluation method, this study investigates fission product migration behavior across leak pathways. Specifically, an experimental line is developed, and experiments are performed under conditions that simulate the environmental and flow conditions in containment vessel penetrations and failure locations during a severe accident. The experiments are conducted in narrow circular pipes, which represent the leak pathways in the containment vessel and reactor building, to determine the impact of flow rate, particle size, and flow path size on the decontamination factors. Additionally, a turbulent deposition model that accounts for re-entrainment effects has been developed, and the experimentally obtained decontamination factors are compared with the developed model, as well as a conventional model. The predicted decontamination factors from the present model exhibit similar trends and values to the experimental results.