FORECASTING OF RADIOACTIVE CONTAMINATION OF ATMOSPHERIC AIR IN AN EXTREME SITUATION AT NPP

Abstract

Problem statement. The task of assessing the level of atmospheric air radioactive contamination in the case of an extreme situation on the territory of the Zaporizhzhya NPP, which leads to an instantaneous radioactive aerosol emission, is considered. An analysis of the dynamics for the zones’ formation of radioactive contamination in the wind direction towards Nikopol is conducted. For the prompt solution of this of this forecast issue, the creation of a multifactorial numerical model is required, which allows for prompt analysis of the size and intensity of radioactive contamination areas. The purpose of the article. Creation of a numerical model and computer code for the operational analysis of radioactive contamination areas formed during the instantaneous release of radioactive pollutants into the atmosphere. Methodology. The computer code is based on a numerical model, which is a differential analogue of the multifactor kinematic equation of mass transfer of a radioactive impurity in atmospheric air. The mass transfer equation takes into account the wind speed field, atmospheric turbulent diffusion, and the intensity of radioactive substances emission into the air. For the numerical integration of the mass transfer equation, the splitting method is used followed by the use of finite-difference schemes. Determination of the volumetric activity value at each splitting step is implemented by an explicit formula. Scientific novelty. An effective numerical model was developed and its software implementation was conducted for operational analysis of the formation of radioactive contamination areas in the atmosphere during an extreme situation at a nuclear power plant, accompanied by the emission of radioactive substances. The model takes into account a complex of factors that affect the process of radioactive impurities spread in the atmosphere. Practical value. A computer code was developed for calculating the dynamics of the formation of radioactive contamination zones in the atmosphere based on the developed numerical model. This makes it possible to analyze the consequences of emergency emissions on the territory of the NPP using the computational experiment method. Conclusions. A mathematical model was developed for the operational analysis of radioactive contamination level of the atmospheric air due to an extreme situation at the nuclear power plant, which leads to an intense instantaneous release of radioactive substances. The results of a computational experiment based on the developed numerical model are presented.