Experimental and Numerical Studies on Colloid-Enhanced Radionuclide Transport - The Effect of Kinetic Radionuclide Sorption onto Colloidal Particles -

Abstract

AbstractNumerous studies have shown that colloidal particles in groundwater can facilitate radionuclide transport in subsurface environments. A series of laboratory experiments was conducted to investigate the effects of radionuclide sorption onto colloids and the surfaces of rock fractures. This research especially focused on the kinetic behavior of the sorption process. A mixed solution of Cs and clay colloids was injected into a single artificial fracture in a granite column. Simulations were also performed to analyze the experimental results using a numerical code, COLFRAC, which describes colloid-facilitated solute transport in discretely-fractured media. The code allows for either equilibrium or kinetic sorption onto the colloidal particles. The experimental and analytical results indicate that transport of Cs is facilitated by the colloidal particles, which can sorb Cs and transport through the fracture. The analyses also illustrate the importance of evaluating parameters that describe kinetic sorption onto colloids. Furthermore, radionuclide transport is likely to be retarded as colloidal particles that sorb radionuclides are filtered on the fracture surface.