Analysis of the Influence of Aerosol Particle Size Distribution on the Behavior of Fission Products during Simulation of an Accident at an NPP with VVER

Due to the potential danger of exposure to aerosol particles on the human body, maximum permissible concentrations of harmful substances are limited by current regulatory documentation. The formation of aerosol particles is possible during beyond design basis accidents at nuclear power plants. The consequences of the radioactive impact of radioactive aerosol particles formed during an accident at a nuclear power plant on the human body are significantly more severe than from the mechanical impact of such particles. An important characteristic of radioactive aerosol particles is their polydispersity (unevenness in size) since particles of different sizes during an accident at a nuclear power plant have different rates of removal from the atmosphere of the nuclear power plant’s containment. Thus, when considering the movement of particles in the containment and the release of aerosol particles into the environment, it is important to correctly model the size distribution of aerosol particles. This paper presents the results of calculating the count and mass distributions of aerosol particles by size in the TOSQAN and Phebus-FP experiments. Methods are given for describing polydisperse systems (using particle size distribution or “average” sizes characterizing the entire distribution) and their influence on processes associated with the transfer of aerosol particles in a containment, and practical recommendations for working with particle size distributions are given. A comparison is made of the use of average size distribution characteristics and the lognormal distribution of aerosol particles to estimate the release during a hypothetical accident at a nuclear power plant with VVER.