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Assessment of Redox Conditions in the Near Field of Nuclear Waste Repositories: Application to the Swiss high-level and intermediate level waste disposal concept

Published online by Cambridge University Press:  01 February 2011

Paul Wersin ,
Lawrence H. Johnson  and
Bernhard Schwyn
Paul Wersin
Affiliation:
National Cooperative for the Disposal of Radioactive Waste (Nagra), 5430 Wettingen, Switzerland
Lawrence H. Johnson
Affiliation:
National Cooperative for the Disposal of Radioactive Waste (Nagra), 5430 Wettingen, Switzerland
Bernhard Schwyn
Affiliation:
National Cooperative for the Disposal of Radioactive Waste (Nagra), 5430 Wettingen, Switzerland
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Abstract

Redox conditions were assessed for a spent fuel and high-level waste (SF/HLW) and an intermediate-level waste (ILW) repository. For both cases our analysis indicates permanently reducing conditions after a relatively short oxic period. The canister-bentonite near field in the HLW case displays a high redox buffering capacity because of expected high activity of dissolved and surface-bound Fe(II). This is contrary to the cementitious near field in the ILW case where concentrations of dissolved reduced species are low and redox reactions occur primarily via solid phase transformation processes.

For the bentonite-canister near field, redox potentials of about -100 to -300 mV (SHE) are estimated, which is supported by recent kinetic data on U, Tc and Se interaction with reduced iron systems. For the cementitious near field, redox potentials of about -200 to -800 mV are estimated, which reflects the large uncertainties related to this alkaline environment.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 807: Symposium Scientific Basis for Nuclear Waste Management XXVII , 2003 , 539
Copyright
Copyright © Materials Research Society 2004

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References

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