[Modeling of different types of size-effect in accumulation of 137Cs in fish from the cooling pond of the Chernobyl Power Plant].

All known types of size-effect in accumulation of radiocesium in fish are described on the basis of the dynamic model of distribution and migration of the radionuclide in aquatic ecosystem. The time-dependent activity of 137Cs in different age classes of carp and pike-perch from the Chernobyl Nuclear Power Plant Cooling Pond is calculated. It is shown that during the first year after the accident the activity of 137Cs in the young generations of fish was higher (negative size-effect) owing to higher feeding rate of young fish. During the following years the increase of activity in the older fish generations takes place (positive size-effect). It is shown that size-dependence is more clear for the predatory species.