Mixing Zone Analysis for River Plumes

Steam power plants which utilize once-through cooling, are required to meet certain mixing zone standards for thermal plumes. Once-through cooling occurs when water is withdrawn from a natural river or lake, and heated water is returned to the same, after condenser circulation. Compliance with regulatory standards during plant operation is often verified from field measurements at specified time intervals. Field data from thermal plume surveys can be used to develop mixing zone models. These are useful in establishing the necessary operating criteria that will assure compliance with the standards during plant operation over the specified range of river flows. A case study is presented illustrating the development of mixing zone models, and the application of such models to evaluate the possible operating criteria for a nuclear power plant at low river flows.