Numerical modelling of 137Cs transport processes in river system

The release of artificial radionuclide ¹³⁷Cs from nuclear power plants is a potential hazard for water environment. A numerical two dimensional model to simulate the transport of ¹³⁷Cs in river has been developed. The model consists of the hydrodynamic sub model, the sedimentological sub model, including several different particle size classes, and deposition and erosion of suspended sediments simultaneously, and the chemical sub model for radionuclide transport in water system. The exchanges of radionuclides between the liquid and solid phases are described in terms of kinetic transfer coefficients. The field measurements of sediment concentration and ¹³⁷Cs activity of 2006 are used for the model validation and the simulation results agree with the measurements well. The model is applied to simulate the transport processes of ¹³⁷Cs discharged from a planned nuclear power plant sited along the Yangtze River. The model results can reflect the detailed of ¹³⁷Cs activity levels in water, suspended matter and bed sediments in the vicinity of the outlet.