Development and Validation of a Correlation for Wet Resuspension Simulation

In case of a postulated severe accident scenario in a nuclear power plant coolant might be released from the cooling circuit into the containment atmosphere. Due to the pressure difference between the cooling circuit and the containment, the fluid will be released gaseous and might contain fission products, depending on the severe accident scenario. The effluent vapour might condensate on the colder containment structures and flow down to the floor, where water pools will be formed. Because of the decay heat of the fission products or due to a pressure decrease in the containment, which might be induced by the operation of filtered containment venting systems, the water pools could start boiling. During this boiling process gas bubbles will rise to the water pool surface and release former solved fission products by bubble bursting into the containment atmosphere. Those released fission products will dry due to their decay heat and remain as very fine particles for a long time in the containment atmosphere. In the context of filtered containment venting system operation a detailed knowledge of those particles is among others of interest for the development of e. g. accident management measures. A correlation for the estimation of the so-called droplet re-entrainment, which is defined as the ratio of the droplet mass flow, released from the bursting bubbles, and the gas flow, which streams through the effective pool surface, is developed and will be validated based on several single effect tests. The considered tests were conducted in test facilities of different scale and investigated the influence of different parameters on the release of aerosols by the effect of droplet re-entrainment. The calculation results are in a good agreement with the experimental data, indicating that parameters with a relevant influence on the droplet re-entrainment are considered in the developed correlation with a suitable impact.