Transverse mixing characteristics of the Missouri River downstream from the Cooper Nuclear Station

The transverse mixing characteristics of the Missouri River in the vicinity of the Cooper Nuclear Station near Brownville, Nebraska, were investigated using the fluorescent-dye tracer technique. Rhodamine WT dye, introduced continuously into the plant once-through circulating-water system, was used to simulate the waste heat. Transverse profiles of dye concentration, depth, and velocity were obtained at several cross sections in the six-mile reach immediately downstream from the plant. The results indicate that the excess temperature in the river at full plant load can be reduced by dilution to less than 50F within a 45-acre mixing zone with the present discharge canal system, provided that the river discharge is not less than about 20,000 cfs. For lower river discharges, some additional mixing would be required to achieve the same reduction. Based on a more detailed analysis of the transverse mixing process, the dimensionless transverse mixing coefficient in the six-mile reach downstream from the plant was found to have average and maximum values that are believed to considerably exceed any previously published values