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Modelling the Long-Term Chemical Evolution of Cement-Groundwater Systems

Published online by Cambridge University Press:  15 February 2011

F. B. Neall
F. B. Neall*
Affiliation:
Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland, neall@psi.ch
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Abstract

The importance of the large volumes of cement and concrete in the planned Swiss L/ILW repository in influencing the chemical environment of the repository and the sorption behaviour of the radionuclides has lead to an interest the long-term evolution of cement-groundwater systems for safety assessment purposes.

A model is presented which simulates the leaching of a column hydrated cement/concrete with fresh groundwater, using a sequential mixing tank approach. The chemical model includes the incongruent dissolution of the CSH-gel phase and reaction of three other cement phases which make up over 90 wt. % of the hydrated cement paste. The model takes account of porosity changes due to dissolution and precipitation. Different concrete compositions can be included in the column in order to represent, for example, a section through a repository cavern. The model can be run as a 1-D flow-through system or as a quasi-1-D system in which flow in any segment is proportional to porosity. Although the model does not include the sophisticated transport models of currently available coupled codes, it does allow the possibility of assessing the duration of high pH conditions within the repository and the influence of different concrete/cement types or different waste type/loading as a first stage to determining long-term transport of radionuclides from the near field.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 412: Symposium V – Scientific Basis for Nuclear Waste Management XIX , 1995 , 483
Copyright
Copyright © Materials Research Society 1996

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References

1. Bradbury, M.H. & Sarott, F.-A., Sorption databases for the cementitious near field of a L/ILW repository for performance assessment, Nagra Technical Report NTB 93-08, Wettingen, Switzerland (1994).Google Scholar
2. Sarott, F.-A., Kunstliche Alterung von Zementstein: Teil I - Experiment, PSI Technische Mitteilung TM-44–95-04,. Paul Scherrer Institute, Villigen, Switzerland (in prep.).Google Scholar
3. Neall, F.B., Modelling of the near-field chemistry of the SMA repository at the Wellenberg site, Nagra Technical Report NTB 94-03, Nagra, Wettingen, Switzerland (1994).Google Scholar
4. Berner, U., A thermodynamic description of the evolution of pore water chemistry and uranium speciation during degradation of cement, PSI Bericht Nr. 62. Paul Scherrer Institute, Villigen, Switzerland (1990).Google Scholar
5. Pearson, F.J. & Berner, U., Nagra thermochemical database: I. Core data, Nagra Technical Report NTB 91-17, Nagra, Wettingen, Switzerland (1991).Google Scholar
6. Pearson, F.J., Berner, U. & Hummel, W., Nagra thermochemical database: I Supplemental data 05/92, Nagra Technical Report NTB 91-18, Nagram, Wettingen. Switzerland (1992).Google Scholar
7. Nagra, , Beurteilung der Langzeitsicherheit des Endlagers SMA am Standort Wellenberg (Gemeinde Wolfenschiessen, NW), Nagra Technical Report NTB 93-26. Nagra, Wettingen, Switzerland (1993).Google Scholar
8. Bogue, R.H., Ind. Engnrg Chem. (Anal.), 1 (4), p. 192 (1929).Google Scholar
9. Berner, U., Mat. Res. Soc. Symp. Proc., 84, p. 319 (1987).Google Scholar
10. Nagra, , Untersuchungen zur Standorteignung im Hinblick auf die Endlagerung schwachund mittelaktiver Abfälle. Geologische Grundlagen und Datensatz zur Beurteilung der Langzeitsicherheit des Endlagers SMA am Standort Wellenberg (Gemeinde Wolfenschiessen, NW), Nagra Technical Report NTB 93-28. Nagra, Wettingen, Switzerland (1993).Google Scholar
11. Pfingsten, W. and Neall, F.B., Modelling the chemistry of an L/ILW repository near-field - Comparison of results from the MCOTAC coupled code and the SEQDISSOLVE reaction path code, PSI Technische Mitteilung TM-44–95-09, Paul Scherrer Institute, Villigen, Switzerland (in prep.).Google Scholar