Measurement of Solute Diffusion Behavior in Fractured Waste Glass Media

Abstract

Determination of aqueous diffusion coefficients of solutes through fractured media is essential for understanding and modeling contaminant transport at many hazardous waste disposal sites. Development of experimental methods and measurements for the characterization of diffusion in fractured glass media is necessary for the design and performance assessment of glassified radionuclear waste disposal facilities. We report on the use of time-lag diffusion experimental method to assess the diffusion behavior of three different solutes (Cs, Sr, and pentafluoro benzoic acid) in fractured, immobilized low activity waste (ILAW) glass forms. A fractured media time-lag diffusion experimental apparatus, which allows the measurement of diffusion coefficients, has been designed and built for this purpose. Use of time-lag diffusion method, a considerably easier experimental method than the other available methods, was not previously demonstrated for measuring diffusion in fractured waste glass media. Hydraulic conductivity, porosity, and diffusion coefficients of a solute were experimentally measured in fractured glass blocks using this method for the first time. Results agree with the range of properties reported for similar rock media earlier, indicating that the time-lag experimental method can effectively characterize the diffusion coefficients of fractured ILAW glass media. Data presented are rare and useful for the design of vitrified glass disposal facilities.