Assessing long-term performance of Category 3 waste cement grouts for radionuclide encasement requires knowledge of the radionuclide-cement interactions and mechanisms of retention (i.e. sorption or precipitation). This understanding will enable accurate prediction of radionuclide fate when the waste forms come in contact with groundwater. A set of diffusion experiments using carbonated and non-carbonated concrete-soil half cells was conducted under unsaturated conditions (4% and 7% by wt moisture content). Spiked concrete half-cell specimens were prepared with and without colloidal metallic iron addition and were carbonated using supercritical carbon dioxide. Spikes of I and Re were added to achieve measurable diffusion profile in the soil part of the half-cell. In addition, properties of concrete materials likely to influence radionuclide migration such as carbonation were evaluated in an effort to correlate these properties with the release of iodine and rhenium.
Revised: February 24, 2007 |
Published: December 15, 2006