Statistical Computational Model of Fission Products Composition of Irradiated Nuclear Fuel and Their Contribution to Gas-aerosol Emissions of Nuclear Power Plants

Abstract

Based on the assumption that the radionuclide composition of gas-aerosol emissions from nuclear power plants (NPPs) into the environment is determined by the composition of the fuel in the reactor (but not identical to it), an analysis of the probability of the occurrence of various isotopes in possible emissions is conducted in this paper. It is confirmed that the activity of nuclear fuel, and consequently the emissions, are determined by uranium fission fragments, proving that the decay rate of radionuclides is proportional to the probability of the appearance of radionuclides with certain mass numbers. It is also shown that there is no functional relationship between the mass yield of radionuclides and their atomic mass, as the variability (fluctuations) in the content of radionuclides in VVER-440 reactor fuel and consequently in NPP emissions reaches 20 orders of magnitude, which prevents the application of computational methods for processing the results. This paper proves that, in order to determine the yield of radionuclides from their observable activity, applying a Zipf-Mandelbrot type distribution in “rank - size” coordinates, it is possible to carry out the mathematical modeling based on the appropriate processing of the obtained results.