Study on Gravity Sedimentation of Multicomponent Hygroscopic Aerosols in Reactor Severe Accident

Abstract

In the event of a severe accident, the multicomponent hygroscopic aerosols in the containment will absorb water under the high humidity condition, thereby influencing the gravity sedimentation behavior. In this study, a physical model of the equilibrium particle diameter of the multicomponent hygroscopic aerosol particles was developed through theoretical analysis, and it was also validated by experimental results. The model focuses on the effect of solubility on the hygroscopic process and explains the reason why the multicomponent hygroscopic particles grow along a discontinuity curve. Based on a typical gigawatt-class pressurized water reactor, the effects of relative humidity, dry particle diameter and mass fraction of hygroscopic components on the removal coefficient of the gravity sedimentation were investigated. The results show that the velocity of the gravity sedimentation will significantly increase, only if the aerosol particles grow to a certain degree. Only when the humidity is more than a certain value, the sedimentation process of the pure hygroscopic aerosol particles with a dry particle diameter exceeding 0.1 μm will accelerate due to hygroscopicity, and this humidity limit will decrease as the dry particle diameter increases. With the progress of the accident, the mass fraction of non-hygroscopic components in the aerosol particles gradually decreases, leading the above-mentioned humidity limit increasing and the acceleration of gravity sedimentation due to the hygroscopicity decreasing in the same humidity.