Architecture and management of a geological repository - Andra

5 – Repository ModulesFigure 5.2.1C waste cell concepts (shaft or tunnel, with or without engineered clay barrier)• Disposal drift or disposal cellThe term "disposal drift" designates a structure in which the useful diameter is significantly higherthan that of the disposal package; the remaining space can be used for handling equipment traffic andfor ventilation of the structure. The disposal cell is on the contrary characterised by a diameter closelytailored to that of the disposal package. The concept of disposal cell is illustrated in Figure 5.2.1. Thedisposal drift concept is illustrated in Figure 5.3.2, which is used for spent fuel.The disposal drift allows direct access to each package during both the operating and monitoringphases; it has no particular advantage after closure. It is penalised by the very large excavated volumeof these cavities. Ventilation of these drifts could allow an increase in disposal density. However itwould not make up for the increased volume excavated. On the contrary the more complex ventilationnetwork would require additional access drifts. Furthermore, the use of ventilation for this purposedoes not comply with the principle of purely passive dissipation of the thermal energy of the packages(by conduction alone).Consequently, only the "disposal cell" configuration is envisaged in the feasibility studies.• Cell with or without swelling clay bufferA concept with a swelling clay engineered structure offers low permeability around the packages,favourable to controlling the environmental conditions of the glass in terms of its dissolution kinetics.This low permeability is maintained for the long-term life of the structure, owing to the deformabilityof the swelling clay and its ability to swell.DOSSIER 2005 ARGILE -ARCHITECTURE AND MANAGEMENT OF A GEOLOGICAL DISPOSAL SYSTEM194/495