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) the mechanism of contaminant release, the significance of contaminant release pathways, how waste form performance is affected by the full range of environmental conditions within the disposal facility, the process of waste form aging under conditions that are representative of processes occurring in response to changing environmental conditions within the disposal facility, the effect of waste form aging on chemical, physical, and radiological properties and the associated impact on contaminant release. This knowledge will enable accurate prediction of radionuclide fate when the waste forms come in contact with groundwater. Numerous sets of tests were initiated in fiscal years (FY) 2006-2009 to evaluate 1) diffusion of iodine (I) and technetium (Tc) from concrete into uncontaminated soil after 1 and 2 years, 2) I and rhenium (Re) diffusion from contaminated soil into fractured concrete, 3) I and Re (set 1) and Tc (set 2) diffusion from fractured concrete into uncontaminated soil, 4) evaluate the moisture distribution profile within the sediment half-cell, 5) the reactivity and speciation of uranium (VI) (U(VI) compounds in concrete porewaters, 6) the rate of dissolution of concrete monoliths, and 7) the diffusion of simulated tank waste into concrete.
Revised: January 10, 2012 |
Published: September 30, 2009