STUDY ON THE CONTRIBUTION OF MAJOR NUCLEAR INCIDENTS TO RADIOACTIVE CONTAMINATION OF THE URAL REGION

Levels of radioactive contamination were studied in natural ecosystems of the Ural region. The soil was shown to contain technogenic radionu clides of different origin. Contributions of Sr-90, Cs-137, and transu ranic elements, which entered the environment after the Kyshtym accide nt in 1957 and were transported by wind from the shores of Lake Karach ai in 1967, were estimated qualitatively. Calculations were based on d irect measurements of radionuclide concentrations in soil samples and on the proposed model assuming an exponential decrease in radionuclide concentrations with the distance from the source of contamination.