Experimental Study On Aerosol Removal Characteristics Of Source Term In Containment

When a serious accident occurs in a nuclear power plant,the reaction between the molten material in the core and the concrete will generate a large number of radioactive fission products of the source term,which eventually converge in the containment.Radioactive fission products exist mainly in the form of aerosols.Once leaked,it will cause great damage to the external environment.Therefore,the radioactive aerosol in the containment needs to be removed.At present,aerosols are mainly removed at home and abroad through the form of natural deposition or the use of spray systems.However,the characteristics of aerosol particles and spray droplets will have a certain impact on its removal.Therefore,it is necessary to carry out research on the aerosol’s natural deposition behavior characteristics and aerosol behavior characteristics under spray conditions.In this paper,TiO₂,BaSO₄ particles,etc.were selected as the aerosol medium,and experiments of natural aerosol deposition characteristics and aerosol spray removal were carried out.The effects of static electricity and quantity concentration on the natural deposition of aerosol particles were studied,as well as the natural deposition characteristics of aerosols with different particle sizes;The removal characteristics of aerosol particles with different particle sizes under spray conditions and the aerosol removal characteristics in different spray areas were studied.The effect of different nozzles on aerosol removal,the impact of spray droplet SMD and type on aerosol removal,and the effect of spray on removal of different types of aerosol.The main conclusions are as follows:In the natural deposition of aerosols,the existence of electrostatic effects will aggravate the polymerization between aerosol particles.The aerosols of small particles polymerize into large aerosols,causing the aerosol particle size spectrum to shift to the right.The natural aerosol deposition rate increases.The deposition rate of aerosols with different particle sizes is also different at different concentrations.The higher the concentration,the faster the deposition rate of aerosols with different particle sizes.When the concentration of aerosol in the container is≥1.5×10⁴/cm³,the influence of polymerization on its deposition must be considered.It takes 13h for the aerosol particles in the container to deposit from 1.5×10⁴/cm³ to the air background.The larger the aerosol particle size,the larger its natural deposition attenuation constant.The aerosol removal rate of the spray system is much faster than the natural aerosol deposition rate.In the spray removal of aerosols,the removal rate of aerosols larger than 1um is much faster than that of aerosol particles smaller than 1μm.As the particle size of aerosols increases,the decay constant decreases first and then increases.When the aerosol particles in the container dropped to 3×103/cm3,the spray droplets no longer affected the aerosol removal.When the flow rate is constant,the smaller the spray droplet SMD,the faster the removal rate of aerosols of various particle sizes.Compared with TiO₂,BaSO₄ is more easily removed by spray droplets.Based on the existing experimental data,the relationship between droplet SMD and aerosol attenuation constant and the relationship between droplet SMD and minimum penetration particle size were obtained.