Modelling the fate of radionuclides in river systems. Study of the Molse Nete-Grote Nete River

The objective was to obtain a dynamic river transport model that can serve as a diagnostic and predictive tool in case of accidental releases. To simulate the radionuclide dispersion, sediment transport and the interactions between radionuclides-water column and sediments have to be considered. As study case, the Molse Nete is considered. In order to represent the radionuclide transport in the river, a Finite Element water quality simulator is developed. The parameters required for the radionuclide-sediment interaction obtained via laboratory experiments. The radionuclide transport simulator was coupled with a river and a hydrological simulator previously calibrated and validated. Then the radionuclide transport model of the Molse Nete-Grote Nete river system was calibrated and validated comparing the measured concentrations of 60Co, 137Cs and 241Am in the river bed sediment with model simulations. Finally the calibrated radionuclide transport model of the Molse Nete-Grote Nete was used to predict the concentration levels of 60Co, 137Cs and 241Am in the dissolved phase and in the bed sediments. The scenarios considered were: the cessation of the routine radioactive liquid releases scenario, the maximum allowed radioactive continuous release scenario and the maximum allowed radioactive continuous release scenario cessation.