Affinity functions for modeling glass dissolution rates

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Glass dissolution rates decrease dramatically as glasses approach "saturation" with respect to the leachate solution. This effect may lower the dissolution rate to 1/100 to 1/1000 of the unsaturated rate. Although rate controls on glass dissolution are best understood for conditions far from saturation, most repository sites are chosen where water fluxes are minimal, and therefore the waste glass is most likely to dissolve under conditions close to saturation. Our understanding of controls on dissolution rates close to saturation, versus far from saturation, are therefore of greater significance for assessing release rates of radionuclides from repositories. The key term in ... continued below

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Bourcier, W L July 8, 1998.

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Glass dissolution rates decrease dramatically as glasses approach "saturation" with respect to the leachate solution. This effect may lower the dissolution rate to 1/100 to 1/1000 of the unsaturated rate. Although rate controls on glass dissolution are best understood for conditions far from saturation, most repository sites are chosen where water fluxes are minimal, and therefore the waste glass is most likely to dissolve under conditions close to saturation. Our understanding of controls on dissolution rates close to saturation, versus far from saturation, are therefore of greater significance for assessing release rates of radionuclides from repositories. The key term in the rate expression used to predict glass dissolution rates close to saturation is the affinity term, which accounts for saturation effects on dissolution rates. The form of the affinity term and parameters used to model glass dissolution are clearly critical for accurate estimates of glass performance in a repository. The concept of saturation with respect to glass dissolution is problematic because of the thermodynamically unstable nature of glass. Saturation implies similar rates of forward (dissolution) and back (precipitation) reactions, but glasses cannot precipitate from aqueous solutions; there can be no back reaction to form glass. However experiments have shown that glasses do exhibit saturation effects when dissolving, analogous to saturation effects observed for thermodynamically stable materials. Attempts to model the glass dissolution process have therefore employed theories and rate equations more commonly used to model dissolution of crystalline solids, as described below

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  • Atomic Energy Commission CEA-VALRHO Vallee due Rhone Summer Workshop, Glass: Scientific Research for High Performance Containment, Mejannes-le-Clap, France, August 31-September 7, 1997

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  • Other: DE00002400
  • Report No.: UCRL-JC-131186
  • Grant Number: W-7405-Eng-48
  • Office of Scientific & Technical Information Report Number: 2400
  • Archival Resource Key: ark:/67531/metadc668212

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  • July 8, 1998

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  • June 29, 2015, 9:42 p.m.

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  • March 23, 2018, 3:52 p.m.

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Bourcier, W L. Affinity functions for modeling glass dissolution rates, article, July 8, 1998; Livermore, California. (digital.library.unt.edu/ark:/67531/metadc668212/: accessed September 18, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.