Validation of Lumped Parameter Code for Aerosol Behavior Analysis in Containment

Abstract

During a severe accident in the pressurized water reactor (PWR), radioactive fission products could be released into the containment building in the form of aerosol. Aerosol deposition in containment has an important influence on source term assessment. Therefore, it is necessary to accurately evaluate the deposition behavior of aerosols in containment.

A lumped-parameter code, containing thermal-hydraulic models and aerosol behavior models, is developed for prediction of aerosol mass concentration in the containment. Thermalhydraulic models consider mass and energy conservation, steam condensation and heat transfer from gas to walls. Aerosol behavior models include aerosol size distribution model and dynamic models, which are used to predict mass, size contribution and composition of suspended aerosols in the atmosphere. The aerosol size distribution model divides aerosol size domain into multi-section, which assumes that it has a log-normal distribution. The aerosol dynamic model treats four agglomeration processes: brown diffusion agglomeration, gravitational agglomeration, turbulent shear agglomeration, and turbulent inertial agglomeration, as well as four deposition processes: gravitational settling, diffusion, thermophoresis, and diffusiophoresis. By comparing prediction results of the code with results of other lumped-parameter codes and experiments, applicability of agglomeration, gravitational deposition, diffusion and thermophoresis models of the code are analyzed in ABCOVE program, while influences of diffusiophoresis deposition mechanism in the containment with humid atmosphere, as well as capabilities of the code, are assessed in Phebus FPT1 experiment. Analysis results show that the code can predict aerosol mass concentration, thermodynamics states and humidity of atmosphere, and the prediction deviation of aerosol size distribution is acceptable comparing to other lumped-parameter codes.