Yuanzineng kexue jishu (Nov 2023)
Experimental Study on Aerosol Removal Characteristics from Wall Surfaces in Condensation Wash-down Environment
Abstract
For the nuclear reactor that experienced a severe radioactive leakage accident, there will be radioactive aerosols dispersed in vapor phase space of the containment vessel. These radioactive substances may deposit on the walls, equipment surfaces, or floors of the containment vessel. Washing by condensate is one of the main removal methods for the re-migration of deposited radioactive aerosol particles. Grasping the removal and migration rules of deposited aerosol particles is of great significance for radiological analysis and evaluation after nuclear accidents. In this paper, the wash-down behavior of aerosols on vertical walls and slightly inclined surfaces is of concern. A visualization experimental setup was established with steam condensation and aerosol deposition environments. The paper conducts an experimental study on the aerosol removal characteristics from wall surfaces in condensing environment. To investigate the effects of wall inclination, condensation rate, and deposition density on aerosol particle removal characteristics, this paper measured the change in aerosol mass during washing removal. The distribution characteristics of condensed water flow on vertical (90°)/ slightly inclined (0.4°, 2°) surfaces were observed through a visual window. The results show that there is wash-down by the rivulet on the 90° and 2° walls, and water film erosion on the 0.4° walls. The removal behavior of deposited particles was discussed in conjunction with the behavior of the condensate. The mass removal rules and removal efficiency (the ratio of washed-down mass to the total initially deposited aerosol mass) of deposited aerosols under different experimental environments were summarized. The results show that as the inclined angle gradually decreases, the time required for the aerosol removal process will significantly increase. On the other hand, a decrease in condensation rate will also increase the removal time of aerosols. In the experimental study, the cumulative removal mass efficiency varies under different environmental conditions, ranging from 78.7% to 96.7%. The study can provide the data support for further verification and optimization of radioactive aerosol transport models.
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