Use of mathematical modelling to estimate scales and study patterns of formation of contaminated areas resulting from a nuclear accident

The 'Typhoon' Scientific and Industrial Association has developed a series of physicomathematical models to describe atmospheric transport and fallout of gaseous and aerosol-form radioactive contaminants for the purpose of studying the processes by which contaminated zones form following discharges into the atmosphere during a nuclear power plant accident. These models are for intermediate range and regional transport and transboundary transport, and they work for distances of ten to several thousand kilometres; they were used to analyse the situation which arose after the Chernobyl accident. These modelling techniques were used to study the space-time characteristics of formation of contaminated areas, to reconstruct the dynamics of the change in parameters of the radionuclide discharge source, and to evaluate the quantity of radionuclides carried beyond the boundaries of the Union of Soviet Socialist Republics after the Chernobyl accident. The source parameters were reconstructed by solving the inverse problem using experimental data on the contamination density at different points. The source strength was evaluated for 131I, 137Cs, 90Sr, 239Pu and 240Pu, and the fallout fields were modelled for separate radionuclides. (author). 11 refs, 5 figs, 1 tab