Environmental modelling of radioactive contamination of floodplains and sorlakes along the Techa and Iset rivers

The radioactive contamination of the Techa-Iset rivers downstream from the MAYAK reservoirs has been determined by measurements of Sr-90, Cs-137 and t ransuranic elements in floodplain soils and sorlake sediments. Empirical mo dels for the spatial distribution of the radioactive contamination in the r iver system were developed by fitting the data to power and exponential fun ctions. The radionuclide inventories calculated from the models were compar ed with Russian data. The models applied in this study predicted higher inv entories than those obtained from the Russian data in the upper reaches of the Techa; but lower inventories were predicted for the downstream part of the river. Estimation of the Sr-90 inventory is encumbered with larger unce rtainties than those of Cs-137 and Pu-239,Pu-240 because the distribution o f Sr-90 does not always follow simple models as do Cs-137 and Pu. The conta mination downstream of MAYAK of the floodplain and Techa-Iset river system was estimated to be 0.1 PBq Sr-90, 0.3 PBq Cs-137 and 0.8 TBq Pu-239,Pu-240 . While essentially all the Cs-137 and Pu outside the MAYAK reservoir are f ound in the Techa river, the Sr-90 contamination extends further downstream . (C) 2000 Elsevier Science Ltd. All rights reserved.