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A case study on the influence of THM coupling on the near field safety of a spent fuel repository in sparsely fractured granite
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2009 (English)In: Environmental Geology, ISSN 0943-0105, E-ISSN 1432-0495, Vol. 57, no 6, 1239-1254 p.Article in journal (Refereed) Published
Abstract [en]

In order to demonstrate the feasibility of geological disposal of spent CANDU fuel in Canada, a safety assessment was performed for a hypothetical repository in the Canadian Shield. The assessment shows that the maximum long term radionuclide release from such repository would meet international criteria for dose rate; however, uncertainties in the assumed evolution of the repository were identified. Such uncertainties could be resolved by the consideration of coupled Thermal-Hydro-Mechanical-Chemical (THMC) processes. In Task A of the DECOVALEX-THMC project, THM models were developed within the framework of the theory of poroelasticity. Such model development was performed in an iterative manner, using experimental data from laboratory and field tests. The models were used to perform near-field simulations of the evolution of the repository in order to address the above-mentioned uncertainties. This paper presents the definition and rationale of task A and the results of the simulations. From a repository safety point of view, the simulations predict that the maximum temperature would be well below the design target of 100A degrees C; however, the stress on the container can marginally exceed the design value of 15 MPa. However, the most important finding from the simulations is that a rock damage zone could form around the emplacement borehole. Such damage zone can extend a few metres from the walls of the emplacement holes, with permeability values that are orders of magnitude higher than the initial values. The damage zone has the potential to increase the radionuclide transport flux from the geosphere; the effect of such an increase should be taken into account in the safety assessment and mitigated if necessary by the provision of sealing systems.

Place, publisher, year, edition, pages
2009. Vol. 57, no 6, 1239-1254 p.
Keyword [en]
Coupled processes, Thermal, Hydraulic, Mechanical, Excavation disturbed zone, Damage, Permeability, In-situ underground experiments, Safety assessment
National Category
Earth and Related Environmental Sciences Other Environmental Engineering
URN: urn:nbn:se:kth:diva-32515DOI: 10.1007/s00254-008-1565-9ISI: 000265622900003ScopusID: 2-s2.0-67349225124OAI: diva2:410950
QC 20110415Available from: 2011-04-15 Created: 2011-04-15 Last updated: 2011-04-15Bibliographically approved

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Jing, Lanru
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Engineering Geology and Geophysics
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