Tome Architecture and management of a geological repository - Andra

6 – C waste repository zoneThe construction activity dimensions the connecting drift number and section in a repository module.Two drifts are envisaged, each of which is dimensioned to enable two workface units to pass: thusthey are 6-8 m wide. These drifts also enable fresh air ventilation (in drift full section) and itsdistribution towards the handling drifts.During module operation, these drifts are reallocated to disposal package transfer.Exhaust air may be ducted through one of the conduits installed in one of the construction drifts inspecific configurations (small dimension module, proximity to main connecting cluster, etc.). In otherconfigurations, a third dedicated exhaust air drift is constructed. Its dimensions are adjusted to moduleventilation requirements.Once again, the connecting drifts present "inverse U" sections to achieve stability without systematicground support. Mechanical perturbation in between connecting drifts (in the pillar) is avoided byconstructing them three times the widest connecting drift diameter apart.A number of simulations have been carried out at this stage, to determine the module exploration andconstruction time. This appears to be longer than the package emplacement period. It takes three tofour years to prepare a 160-180-cell module for reference packages C0, filling taking two years, whileit takes four to five years to prepare a 600-660-cell module for reference packages C1-C4, fillingtaking two years too.Module construction time does not increase in proportion to the number of packages to be emplaced:the larger a module, the more optimised can be construction work scheduling through varioussimultaneous work faces.6.5.3 Assessing the number of C waste modulesIn the absence of specific site data, an estimate of the required number of modules can be made byconsidering those modules whose mean capacity corresponds to filling in two years (about 600 cells):for scenario S1a (or S1b), 32 modules of this type are needed, including 5 for reference packages C0.This number increases to 37 for scenario S1c, and to 14 for scenario S2 (spent fuel reprocessing isstopped). About twenty blocks would have to be identified for two-level architecture.In a more demanding site configuration on the fracturing viewpoint, smaller modules, operated forabout eighteen months can be envisaged (about 450 cells). Thus the number of modules to beconstructed would vary from about 40 for scenario S1c to about 20 for scenario S2.C waste repository zone architecture entails organisation of clusters of primary and secondaryconnecting drifts suitable for dealing with the spread of ten to twenty modules on each repositorylevel.These more or less ramified solutions (cf. § 4.2), should provide a flexible and gradual management ofthe disposal process by enabling various simultaneous activities associated with exploration,construction, operation and closure of modules distributed in various points of the repository zone.Assessments of the waste repository zone area developed on both levels for a defined site can becalculated for each study scenario in line with the mean distance between neighbouring modules. Thisdistance is specified during the site exploration work (surface and laboratory work).Dossier 2005 granite - ARCHITECTURE AND MANAGEMENT OF A GEOLOGICAL REPOSITORY181/228