Abstract
AbstractThe Nuclear Decommissioning Authority Radioactive Waste Management Directorate have been participating in the current DECOVALEX-2011 project (development of coupled models and their validation against experiments) one task of which has been examining the Mont Terri Ventilation Experiment (VE). This long-term (>9 years), field-scale experiment in the Opalinus Clay near the Swiss–French border, was designed to examine the coupled hydraulic–mechanical–chemical changes caused in the tunnel and in the surrounding geology, by the controlled ventilation of a 1.65 m diameter micro-tunnel.In contrast to many conventional benchmarking and validation exercises, a key aspect of the VE as examined in DECOVALEX was that some data were held back and participants were required to make predictions of key metrics for the future evolution of the system. This paper presents an overview of the work conducted by the Quintessa and University of Edinburgh team including selected results. The coupled models developed include multiphase flow, elastic deformation and chemical processes in both detailed and upscaled geometries.The models have been able to replicate the observed desaturation around the tunnel, tunnel deformation and localized failure, vapour migration in the tunnel, and the transition in redox conditions into the host rock.
Highlights
THE performance and safety assessments of a disposal facility in a deep geological formation are supported to a large extent by the ability of the proponent to demonstrate a good fundamental understanding of the evolution of the system under construction, disposal and closure conditions
Demonstration and development of this understanding is heavily based on experimental investigations, which are conducted in the field, in dedicated underground research laboratories
The results suggest that the hydro-mechanical model represented the available data well, and included a representation of the tunnel which allows the true boundaries of the experiment to be modelled directly
Summary
THE performance and safety assessments of a disposal facility in a deep geological formation are supported to a large extent by the ability of the proponent to demonstrate a good fundamental understanding of the evolution of the system under construction, disposal and closure conditions. The reference model used an effective liquid pressure boundary condition (pl) based on Kelvin’s Law in the chamber (equation 3) and produced results that were a good fit to the observed water contents, taking into account heterogeneity between the samples (Fig. 5).
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