An Analysis of Buffering in Bentonite-Groundwater Systems

by R. C. Arthur, Battelle, Richland, United States,
M. J. Apted, Battelle, Richland, United States,
H. Umeki, Battelle, Richland, United States,
H. Takase, Battelle, Richland, United States,
M. Yui, Battelle, Richland, United States,

Document Type: Proceeding Paper

Part of: High Level Radioactive Waste Management 1991


Chemical buffering by bentonite can potentially simplify assessments of the performance of engineered barriers to radionuclide migration by decoupling near-field and far-field geochemical regimes in geologic repositories. Mass transfer calculations that account for smectite's crystalline-solution behavior demonstrate that buffering by bentonite minimizes many of the effects on fluid compositions caused by prior water-rock interactions in the far field. Buffering is manifested by simultaneous changes in the compositions of both smectite and water that are driven by concurrent irreversible dissolution of accessory minerals. Calculated equilibrium states in bentonite-groundwater systems can be validated using a regular solution model.

Subject Headings: Bentonite | Water resources | Chemical grouting | Groundwater pollution | Radioactive materials | Coupling | Geology | Minerals

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