The assessment of the radiological impact of the liquid discharges from nuclear power plants is a major issue for the environmental protection.In this study,a nuberical model for the radionuclide transport in the aquatic enviroument is built,based on the hydrodynamic equations,including the complete set of Saint-Venant equations,the sediment transport equations,with consideration of several different particle sizes and the deposition and erosion of the suspended sediments,and the radionuclide transport equations.The exchanges of radionuclides between water,suspended matter and bed sediments are described in terms of kinetic transfer coefficients.The model is used to simulate the transport of the radionuclides discharged from a planned nuclear power plant project to be sited along the lower Yangtze River.From the model results,one may see the detailed temporal-spatial evolution of the radionuclide contamination in the solution,in the suspended matter and in the bed sediments.The model can be used as a basic tool for studying the environmental impacts of the liquid discharges from nuclear facilities on a river system.