Coupled THMC Modelling of Single Fractures in Novaculite and Granite

Bond, Alexander (Quintessa Ltd.) | Chittenden, Neil (Quintessa Ltd.) | Fedors, Randall (United States Nuclear Regulatory Commission) | Lang, Philipp (Imperial College London) | McDermott, Christopher (University of Edinburgh) | Neretnieks, Ivars (KTH) | Pan, Peng-Zhi (Chinese Academy of Sciences) | Sembera, Jan (Technical University of Liberec) | Brusky, I. (Technical University of Liberec) | Watanabe, Norihiro (Helmholtz Centre for Environmental Research - UFZ) | Lu, R. (Helmholtz Centre for Environmental Research - UFZ) | Yasuhara, H. (Ehime University)

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The evolution of fracture permeability can have important impacts for the resaturation of the facility and long-term transport of any radionuclides that escape the immediate area of disposal. Whereas such systems have been looked at both within the DEvelopment of COupled models and their VALidation against EXperiments (DECOVALEX) project and elsewhere, attempts to model a fully-coupled THMC system on a single fracture have been limited. Examples where THMC analysis in fracture rock has been addressed include Yasuhara and Elsworth (2006), Taron et al. (2009) and Zhang (2012), but with the exception of Yasuhara and Elsworth (2006), the emphasis has been largely on theoretical studies, with no direct comparison against well-constrained small-scale experimental data. There is however a large body of knowledge concerning THM behavior with non-reactive transport in fractures (e.g. Berkowitz, 2002; Neuman, 2005) and a wide range of work examining chemical interactions in fractured systems (e.g. Watson et al., 2016) but modelling efforts incorporating THM and C processes for single fractures are rare. The objective of this Task (Task C1: one of 5 Tasks in the previous phase of DECOVALEX; please see www.decovalex.org for more information on DECOVALEX including numerous examples of this type of collaborative research) is to use the experimental data of Yasuhara et al., 2006 and 2011 to model evolving single fractures incorporating coupled THMC effects for novaculite (quartzite) and granite fractures. This work is not focused on blind prediction, rather it is concerned with building experience and understanding of the physical processes in operation in single fractures on the basis of experimental data and to understand how to represent such processes through numerical and/or semi-analytical models. The Task has had significant technical contributions from six teams (abbreviations, where used, are shown in bold), as well as input from Neretnieks, 2014 and Sandia National Laboratory: - BGR/UFZ - Germany-Federal Institute for Geosciences and Natural Resources and the Helmholtz Centre for Environmental Research.