Particle Resuspension Model for Subatmospheric Conditions

A large amount of metal dust in beryllium and tungsten are produced owing to the interaction between the plasma and the first wall during normal operation of a fusion facility, and deposit on the inner surface of the vacuum vessel. In accidental scenarios such as loss of vacuum accident, the deposited dust particles are mobilized by the subatmospheric ingress airflow and form a flammable and potentially explosive dust cloud, which poses a risk to the fusion facility. In order to estimate the fraction of the mobilized dust, the mechanism of particle resuspension must be well understood especially for the rarefied flow conditions. A classical force balance model for particle resuspension in atmospheric conditions is reviewed and extended in this paper to the regime of rarefied conditions by correcting the aerodynamic drag force in terms of the specific Knudsen number of the rarefied flow. The newly developed model can predict the threshold bulk flow velocity for particle resuspension in subatmospheric conditions, which can be further applied to estimate the fraction of mobilized dust.