Architecture and management of a geological repository - Andra

5 – Repository ModulesFigure 5.1.20Ventilation of the B cell pending sealingThe ventilation creates little mechanical or chemical disturbance within the cells (see chapter 10.2).Desaturation of the rock wall by relatively dry air in fact tends to increase the mechanical strength ofthe cell, without extending the damaged rock zone in the vicinity [57], oxidization of the argilites bythe air infeed remains extremely limited to a heavily desaturated zone about a decimetre thick.furthermore, the disruptions linked to oxidisation of the metal materials present in the cell areconsiderably limited by the small quantity of metals introduced into the cell (apart from the package)and the degradation of concrete by atmospheric carbonation only concerns a maximum thickness ofabout a centimetre, in particular because of the low porosity of HPC concrete.5.1.3.9 Compatibility of the design with the disposal package emplacement methodThe design of the cell is inseparable from that of the package handling and emplacement system. Inthis respect, two elements are of considerable significance: the compatibility between the functionalclearances and the performance of the handling equipment, and the approach to personnel radiologicalprotection during disposal operations.With regard to functional clearances, minimising the residual spaces within the cell requires that thepackages be positioned and stacked with considerable precision (about a few centimetres). Thepositioning principle envisaged for the transporter (described in chapter 9 covering operationalsystems) is based on the use of coders and sensors, possibly backed up by a laser system. Equipmentsuch as this, which is commonly used in industry, guarantees that the goal of minimising clearancewill be consistent with the performance of the envisaged handling system.With regard to radiological protection during package transfer from the surface installations to thecells, the personnel are protected initially by transport transfer casks and then by the cell headchamber. The cell transporter is remote-controlled and the personnel do not enter the chamber duringpackage emplacement operations. The transporter extracts the package from its transfer cask, transfersit to the disposal chamber and positions it.5.1.4 Layout of different types of B waste cellsStandardisation of the disposal packages presented in chapter 4 enables several different package typesto be grouped in the same cell (co-disposal). Given what we currently know, certain groupings arenonetheless avoided in order to limit potentially harmful interactions in terms of release ofradionuclides [61].DOSSIER 2005 ARGILE -ARCHITECTURE AND MANAGEMENT OF A GEOLOGICAL DISPOSAL SYSTEM182/495