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)

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). 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. (author)