Importance of the Excavation Damaged Zone (EDZ) in the General Performance of the Near-Field of a Geological Disposal Sy
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Importance of the Excavation Damaged Zone (EDZ) in the General Performance of the Near-Field of a Geological Disposal System; Input of the EDZ Component to the EC Integrated Project on the Near-Field (NF-PRO) Jean François Aranyossy1, Peter Blümling2, Hans Joachim Alheid3, Maarten Van Geet4, Juan Carlos Mayor5, Paul Marschall2 and Frederic Plas1 1 Agence nationale pour la gestion des déchets radioactifs (Andra) Parc de la Croix Blanche, F-92298 Châtenay-Malabry, France. 2 National Cooperative for the Disposal of Radioactive Waste (Nagra) Hardstrasse, 73, CH-5430 Wettingen, Switzerland. 3 Bundesanstalt für Geowissenschaften und Rohstoffe (BGR) Stilleweg 2, PO box 510153, 30631 Hannover, Germany. 4 Studiecentrum voor Kernenergie - Centre d'étude de l'énergie nucléaire (SCK•CEN) Waste & Disposal Department, Boeretang 200, B-2400 Mol, Belgium. 5 Empresa Nacional de Residuos Radiactivos S.A (Enresa) Emilio Vargas, 7, 28043 Madrid, Spain.
ABSTRACT In order to tackle the particular issues presented by the existence of an Excavation Damaged Zone (EDZ) along disposal cells and tunnels and the subsequent potential occurrence of preferential flow paths and radionuclide migration, a specific Component on the EDZ has been incorporated into the EC Integrated Project on the Near-Field (NF-PRO)1. This Component is organised into several Work Packages matching the foreseeable EDZ evolution during the repository lifetime: (i) the "initial phase", corresponding to EDZ development induced by underground excavations and rock stress release; (ii) the "transient phase", corresponding to the repository operating phase, mainly characterised by desaturation, temperature increase and resaturation processes; (iii) the "long-term phase", corresponding to the post-closure repository period, mainly characterised by EDZ self-sealing / self-healing and gas transport processes. The scientific results obtained through the numerous tasks included in the Component cover various aspects of EDZ investigation (desk studies, experimental work on representative rock samples, in situ experiments in URLs, numerical modelling) and are integrated into a global EDZ impact evaluation to be forwarded to the Component of the project devoted to process coupling and integration in the general performance assessment of the near-field.
INTRODUCTION The construction of underground facilities in all types of rock potentially used to host nuclear waste repositories (salt, granite, indurated and soft clays) results in the creation of a damaged zone (EDZ) and a disturbed zone (EdZ) around the openings [1] (Figure1). The development and evolution of these zones depend, together with the excavation and support methods, on the hydro-mechanical properties of the host rock, its in situ stress and porewater 1
NF-PRO: Understanding and physical and modelling of the key processes in the near-field, and their coupling, for different host rocks and repository strategies
pressure distribution. In the long-term, EDZ evolution may also be influenced by heat released from the waste
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