LONG-TERM STUDY ON THE TRANSFER OF CS-137 AND SR-90 FROM CHERNOBYL-CONTAMINATED SOILS TO GRAIN CROPS

The level of Cs-137 and Sr-90 transfer to four grain crops and the cha nge in transfer with time have been studied on two soils contaminated with fragments of nuclear fuel released during the Chernobyl accident. Field experiments were carried out in 1987-1994 inside the heavily co ntaminated zone around Chernobyl Nuclear Power Plant. Shortly after th e deposition, the rate of Sr-90 accumulation by crops was comparable w ith, or even slower, than that of Cs-137, which is in disagreement wit h the usual findings. In the following years, Cs-137 uptake by plants was reduced by a factor in excess of than 50, whereas the soil-to-plan t concentration ratio of Sr-90 increased within one order of magnitude , and has remained on approximately the same level since 1991. Changes of the Sr-90 and Cs-137 concentration ratios for grain crops with tim e have been used to evaluate the rate of radionuclide leaching from fu el particles and the ageing processes. Copyright (C) 1996 Elsevier Sci ence Limited.