Tome Architecture and management of a geological repository - Andra

5 – B waste repository zoneFigure 5.4.1View of a disposal cell5.4.1.1 The disposal chamberLarge-dimension mechanically stable sections can be envisaged underground in a granite medium.Thus disposal chamber sections correspond to a compromise between the need for compactness 30 ,operational safety considerations, primarily regarding package drop hazards and temperature controlfor slightly exothermic B waste.This compromise leads to distinguishing two types of disposal chamber: large-section chambers, aboutten metres high and up to 25 m wide, and smaller width chambers (about 10 m across) thataccommodate slightly exothermic B waste packages.The disposal chamber profile has the dual aim of stability without the need for rock support and ashape that reduces the excavated volumes not utilised for disposal. Thus the envisaged shape is an"inverted U", with a very slim arch.The chamber slab comprises a plain concrete layer on top of which the final layer rests, incorporatingrails for the package handling fork-lift trucks. The slab incorporates the ventilation exhaust air anddrainage water pipes.The cell end has a perforated concrete wall behind which arrive return air pipes.5.4.1.2 The cell headThe cell head at the entrance to the disposal chamber has a radiological protection air-lock (dual-gatesystem) to allow disposal tunnel operations. This airlock comprises two gates through which thedisposal packages are transferred between the operator-accessible access drift and the disposalchamber, which is inaccessible to personnel as it is an irradiating zone.30The compactness mentioned here refers to the ratio between emplaced waste volume and disposal chamber volume.Dossier 2005 Granite - ARCHITECTURE AND MANAGEMENT OF A GEOLOGICAL REPOSITORY129/228