Abstract
To evaluate colloidal migration of radionuclides through geologic media in groundwater, a calculation code has been developed. Four reaction models, i) instantaneous equilibrium, ii) first order kinetic reaction, iii) filtration, and iv) first order kinetic reaction with filtration capacity, have been discussed on their applicability to colloid transport through porous media on the basis of breakthrough curves from column experiments using sand and reddish soil. The instantaneous equilibrium model could not explain both time course and increase rate of breakthrough curve approaching to CC/CCo=1, however the first order kinetic reaction model, as one of models having the property of blocking effect, successfully simulate them. Breakthrough curves from the reddish soil column have a specific behavior showing step-wise pattern of colloid concentration in response to repeated inflow of colloid. The instantaneous equilibrium, the first order kinetic reaction, and the filtration models could not explain this behavior. However the first order kinetic reaction with filtration capacity model reasonably simulates the breakthrough curves with specific behavior. As a basis of colloidal migration model of radionuclides in natural barrier, the colloid transport model has been evaluated its applicability through the laboratory experiments.
