Architecture and management of a geological repository - Andra

2 – General DescriptionFigure 2.4.5Sealed B waste disposal cell2.4.2.2 Waste disposal packages and cells for vitrified C wasteTo prevent the inflow of water onto the waste during the thermal phase, each primary package ofvitrified waste is placed in a watertight over-pack throughout this phase. This over-pack is made ofnon-alloy steel with an effective thickness of 55 millimetres, dimensioned very conservatively towithstand corrosion for a thousand years. A detailed description of the over-pack is provided insection 4.2. The mass of the standard disposal package is almost 2 tonnes (package types C1 to C4).The design of C waste disposal cells is the result of (i) the search for a physical and chemicalenvironment suited to the packages, and (ii) the thermal design associated with heat dissipation byconduction through the rock. As a result, the thermal load per unit of surface area is limited not onlyon a repository scale but also on a cell scale.C waste disposal cells are dead-end, horizontal bore-holes with an excavated diameter ofapproximately 0.7 metre. At this stage, their length has been limited to around 40 metres, a lengthconsidered reasonable in view of construction and handling techniques – see section 5.2. They have ametallic sleeve which supports the argillites and enables package handling for their emplacement andpossible future retrieval. They contain from 6 to 22 disposal packages..Packages characterised by moderate thermal power may be disposed side by side – this is the case ofpackage type C0.For packages with higher thermal power (package types C1 to C4), a conceivable storage period priorto emplacement in the repository has been determined in order to limit thermal disturbance. Theduration of this storage period is 60 to 70 years depending on the package. After such a storage period,the residual thermal power of these packages still requires them to be separated by spacers in a singledisposal cell. In any case, we have yet to conduct an optimisation process at this stage.DOSSIER 2005 ARGILE -ARCHITECTURE AND MANAGEMENT OF A GEOLOGICAL DISPOSAL SYSTEM61/495