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Hydrothermal Simulation of Ion Migration in Selected Argillaceous Sediments: Implications For Backfill Design

Published online by Cambridge University Press:  21 February 2011

Lisa Bratton ,
Barry E. Scheetz  and
William B. White
Lisa Bratton
Affiliation:
Materials Research Laboratory, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
Barry E. Scheetz
Affiliation:
Materials Research Laboratory, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
William B. White
Affiliation:
Materials Research Laboratory, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
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Abstract

Argillaceous rocks, used either as a repository rock or as a backfill material provide a reactive medium with which escaped radionuclides can react. Solutions containing U, Nd Gd, Cs, and Sr were reacted with bulk specimens of two argillites with the objective of determining penetration of heavy metals into the rock, and the reaction products. The two Devonian argillites were chosen to represent a highly reducing rock containing pyrite and carbonaceous material as accessory minerals, and a clean, alumino-silicate rock containing mainly quartz and layer silicates. Cylinders of rock were reacted with solutions at saturated steam pressures and 200°C.

At the end of the runs, both rocks contained reduced uranium in the form of U02.25. The rare earths were associated with the uranium. There was a precipitated coating of uranium-rich material on the outside of the reducing shale and few of the radionuclides had penetrated the interior. Uranium also formed a precipitate within 0.5 mm of the surface of the oxidized shale leaving a depleted zone near the surface. Cesium and strontium did not penetrate the reducing shale but were uniformly distributed throughout the oxidized shale. Chlorite, apatite and pyrite were found to be the most reactive phases in the shales.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 15: Symposium D – Scientific Basis for Nuclear Waste Management VI , 1982 , 769
Copyright
Copyright © Materials Research Society 1983

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References

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