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Glass Surface area to Solution Volume Ratio and its Implications to Accelerated Leach Testing*

Published online by Cambridge University Press:  21 February 2011

Larry R. Pederson ,
Charles Q. Buckwalter ,
Gary L. Mcvay  and
B. Lynn Riddle
Larry R. Pederson
Affiliation:
Pacific Northwest Laboratory, P. O. Box 999, Richland, Washington, USA
Charles Q. Buckwalter
Affiliation:
Pacific Northwest Laboratory, P. O. Box 999, Richland, Washington, USA
Gary L. Mcvay
Affiliation:
Pacific Northwest Laboratory, P. O. Box 999, Richland, Washington, USA
B. Lynn Riddle
Affiliation:
Pacific Northwest Laboratory, P. O. Box 999, Richland, Washington, USA
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Abstract

Leaching tests of PNL 76–68 glass in deionized water have been performed using the standard MCC-l static leaching procedure but with varied glass surface area to solution volume ratios (SA/V). It was found that leaching could be strongly influenced by the SA/V ratio, due largely to an effect of silicon solubility limitations. The conclusion that solubility and not solid state diffusion is most important in regulating leaching rates is supported by (1) the similarities in depth profiles of all soluble glass components with none depleted to depths greater than that of silicon despite vastly different solid state diffusivities, and (2) the lack of dependence of leaching rates on reaction layer thicknesses. To more directly examine the influence of dissolved silicon on glass leaching rates, leaching tests were performed in silicic acid solutions and in two actual groundwaters. As expected, leaching rates of all soluble glass components were reduced by amounts roughly proportional to the silicon saturation fraction. Since solubility modifies leaching rates in all but very dilute solutions, short-term tests at high SA/V values can be used to predict solution concentrations for long-term tests at low SA/V values, although reaction layers formed are not of the same thickness. Glass leaching data for a range of leaching times and SA/V values can be represented by a single curve when plotted versus the product of SA/V and time. However, the use of SA/V variations may have limited usefulness in accelerated leach testing for multicomponent systems. Events such as silica colloid and certain alteration phase formations modify the above relationship.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 15: Symposium D – Scientific Basis for Nuclear Waste Management VI , 1982 , 47
Copyright
Copyright © Materials Research Society 1983

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Footnotes

*

Work supported by the U.S. Department of Energy under contract DE-AC06-76RLO 1830.

References

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