Assessment of Film Drop Release From Liquid Pools by an Empirical Correlation Approach

The present work deals with the topic of wet resuspension, particularly with regard to the basics of film drop release from bubbles and its impact on the aerosol source term as well as with the development of an empirical correlation approach adapted to the containment code system COCOSYS at low atmosphere motion. Film drops are discharged from the lamella of a bubble during the disruption process, while the bubble is resting at the fluid surface. Besides the description of the bubble disruption process, factors which have an influence on the mass and size distribution of the drops released from the bubble lamella are discussed. To analyse the distribution of the film drops of different bubble sizes, measured film drop distributions of several bubble diameters were collected from the literature. The analysis shows that with the presence of surfactants (surface-active agents) a log-normal count distribution can be used for the approximation of the drop distribution. By the evaporation of the liquid of the released film drops the solved and/or suspended materials remain as particles. In dependence of their size the drops or particles are airborne or fall back onto the liquid pool surface. The remaining airborne drops/particles are able to contribute in the late phase of a severe accident to the source term, if they are radioactive.