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Porosity distribution in a heterogeneous clay-rich fault core by image processing of 14C-PMMA autoradiographs and Scanning Electron Microscopy

Published online by Cambridge University Press:  17 December 2017

Ville Nenonen*
Affiliation:
Laboratory of Radiochemistry, University of Helsinki, Helsinki, Finland
Juuso Sammaljärvi
Affiliation:
Laboratory of Radiochemistry, University of Helsinki, Helsinki, Finland
Bo Johanson
Affiliation:
Geological Survey of Finland (GTK), Espoo, Finland
Mikko Voutilainen
Affiliation:
Laboratory of Radiochemistry, University of Helsinki, Helsinki, Finland
Emilie L’Hôpital
Affiliation:
Institut de Radioprotection et de Sûreté Nucléaire (IRSN), Fontenay-aux-Roses, France
Pierre Dick
Affiliation:
Institut de Radioprotection et de Sûreté Nucléaire (IRSN), Fontenay-aux-Roses, France
Marja Siitari-Kauppi
Affiliation:
Laboratory of Radiochemistry, University of Helsinki, Helsinki, Finland
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Abstract

Shale formations are considered by a number of countries as the most suitable media to dispose of high-level radioactive waste. This is mainly due to the impermeable, self-sealing, chemical reducing, and sorption properties that tend to retard radionuclide migration. However, shale formations can also contain highly connected fault zones with permeabilities that can differ of several orders of magnitudes with respect to the undeformed host rock. The objective of this work is to use the 14C-PMMA autoradiography method combined with SEM-EDS measurements to understand the porosity variations in and around fault gouges and to define their relationship to mechano-chemical processes. The studied samples were taken from a low permeability shale in a small-scale vertical strike-slip fault at the Tournemire underground research laboratory. Results display significant variations in porosity and mineralogy along the studied gouge zone due to polyphased tectonics and paleo-fluid circulations.

Type
Articles
Copyright
Copyright © Materials Research Society 2017 

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