Selection of Radioactive Aerosol Distribution
Models Inside and Outside the New Safe Confinement
of the ChNPP

P. G. Krukovskii, V. S. Oliinyk

Institute of Technical Thermophysics of the National Academy
of Sciences of Ukraine, 2а, Maria Kapnist st., Kyiv, 03057, Ukraine

DOI: doi.org/10.31717/2311-8253.22.3.5

Abstract

The New Safe Confinement (NSC) is a facility that protects the environment from radioactive aerosols (RA) during the extraction of radioactive materials. However, it is not able to provide complete insulation of the internal volume, therefore, to reduce the damage. It is necessary to use auxiliary means, such as ventilation, a special microclimate inside, etc., but this reduces, not eliminates RA leaks. The paper considers approaches for control and the possibility of minimizing RA emissions by simultaneous modeling of the distribution of RA both inside a relatively small volume of the NSC of the Chornobyl NPP (ChNPP) using an internal model, and in the vicinity of the NSC with the help of an external model. The internal and external models are significantly different because RA inside the NSC are distributed by convective air currents very slowly and settle on an area of approximately 0.03 km2 , while outside of the ChNPP industrial site they are intensively distributed by fast multidirectional wind currents and settle on a significant area of approximately 3 km2. This leads to significant differences in the requirements to internal and external models. Differences were found in such categories as parameters of RA source, topology and dimensions of simulation volume, time step for transient simulation, computation speed requirements, spatial resolution of the mesh etc. Three most popular approaches of RA distribution modelling were analyzed — three-dimensional internal and external CFD models, external models of the Gaussian plume and dispersion of Lagrangian particles. Each has an advantage in some categories and disadvantages in others, based on this trade-off, the suitability of the models is judged. Another important requirement is inside-outside models integration with the following communication scenario: outside model is to provide pressure map on the NSC exterior shell at different weather conditions; inside model is to calculate RA generation rate and distribution to holes (leaks in the NSC structure); with known RA source at the leaks, outside model assesses RA deposition on the surface of interest (industrial site).

Keywords: radioactive aerosols, radiation propagation, Chornobyl nuclear power plant, modeling, thermogasodynamic state

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