KINETICS OF RADIONUCLIDE INTERACTION WITH SUSPENDED-SOLIDS IN MODELING THE MIGRATION OF RADIONUCLIDES IN RIVERS .3. VARIABILITY OF KINETIC-PARAMETERS

The effect of variable composition of water and suspended solids in a small river on the kinetics of uptake of Co-58 and Cs-137 by the solid s has been analyzed using two kinetic models describing the uptake by two consecutive or parallel reactions. At first, experimental data on the kinetics were obtained by laboratory batch experiments with 6 samp les of unfiltered water taken under different flow conditions. Then, p arameters of the kinetic models were determined by computer fitting of the experimental data. After subtracting the effect of the concentrat ion of the solids, the variability of the parameters due to the variab le composition was determined. The results proved that despite the var iability, the description of the kinetics by the two-step kinetic mode ls is more accurate than that using a one-step kinetic model. Approxim ately equal accuracy of the description with both two-step kinetic mod els was ascertained. It is recommended that kinetic and equilibrium pa rameters of radionuclide uptake by suspended solids should always be d etermined by experiments with repeatedly sampled unfiltered water.