Tome Architecture and management of a geological repository - Andra

5 – B waste repository zoneIn two-level repository architecture, installing the thermal package tunnels on the upper level (wherethe temperature of the massif is cooler) is preferred for a compact repository. This upper level in thereference architecture is about 400 m deep where the temperatures of the massif should be 2-4°Clower than those considered in the calculations.Disposing of 18 packages per section of exothermic waste tunnels at a depth of about 400 m in granitewith "medium" thermal characteristics is thus adopted as the reference.Adapting this reference to real site conditions that deviate from those considered here as average, willaffect the number of packages per tunnel section, which finally will have a consequence on tunnellength to be constructed for all the slightly exothermic waste.The reference tunnel comprises disposal chambers with an excavated section of 80-85 m 2 , for stacking18 disposal packages in 5 columns, with 4 levels in the central part and 3 levels along the side walls 32Figure 5.4.7Cross-section of a disposal tunnel of slightly exothermic wasteThe construction details are similar to those of the large diameter tunnels (bolts and shotcrete used toensure excavation site safety, slab cut to slope slightly towards the centre of the tunnel, spacingbetween the columns of packages).Assessment of overall disposal chamber length results in the following figures for the groupings ofwaste and for each scenario:32In the event of significant stress anisotropy (σ H /σ V > 2), geo-mechanical stability calculations could examine geometry enabling thepackages to be stacked on 7 columns with only 3 levels in the central part.Dossier 2005 Granite - ARCHITECTURE AND MANAGEMENT OF A GEOLOGICAL REPOSITORY135/228