For passive nuclear power plants, the radioactive aerosols in containment are removed by natural processes after accidents. These processes have high reliability. However, it is very complicated to analyze the behaviors of aerosols in natural processes. The dominant processes include coagulation, sedimentation, diffusionphoresis, and themophoresis. The main work of this paper is summarized as follows: (1) To determine methods of analysis radioactive aerosol natural removal coefficient in containment. (2) To complete comparative analysis natural removal processes to AP1000 and CAP1400 after LOCA. (3) A comprehensive sensitivity analysis is carried out for a number of parameters, including containment free volume, sedimentation area, aerosol size, packing fraction, mass ratio of radioactive and nonradioactive aerosol, and steam condensation rate etc, (4) To complete comparative analysis of natural removal processes between core meltdown and non-meltdown accident sequence after LOCA. The results show that, (1) Removal coefficient by sedimentation of CAP1400 is larger than AP1000, removal coefficient by diffusionphoresis and themophoresis of CAP1400 also smaller than AP1000. (2) In general, the greater the containment free containment, the smaller the aerosol natural removal coefficient, and the greater aerosol size, the more the amount of aerosol removed by sedimentation, in the case of other parameters unchanged. (3) The removal coefficients have few differences after core meltdown and non-meltdown accidents.

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