Modelling of decontamination factor in swarm flow based on residence times

• New approach is introduced to model the decontamination factor based on the statistical treatment of the bubble and particle residence times. • Two different groups of CFD simulations are carried out to investigate the bubble and particle removal behaviours, respectively. • Probability density functions of both bubble and particle removal behaviours can be well represented with simple exponential decay functions. Pool scrubbing process is an important measure to minimize the radioactive material release in the containment. Decontamination factor describes the efficiency of aerosol removal in the pool scrubbing process and requires reliable modelling and prediction. In the existing aerosol retention code, conventional approaches are applied, which rely on the deposition velocity of particles at the interfacial area. During the pool scrubbing process, both gas bubble topology and movement show a strong dynamic behaviour and cannot be well described using simple models. This leads to a big deficiency in reliable modelling of the decontamination factor. To overcome this difficulty, a new approach is introduced in this paper to model the decontamination factor based on the statistical treatment of the residence time of bubbles in the liquid pool as well as the residence time of particles inside bubbles. Two different groups of CFD simulations are carried out to investigate the bubble behaviour in the water pool and the particle transportation inside bubbles, respectively. The numerical results achieved so far indicate that the probability density functions of both bubble removal and particle removal can be well represented with simple exponential decay functions. Thus, the good feasibility of the new modelling approach is successfully confirmed.