Architecture and management of a geological repository - Andra

5 – Repository ModulesAlthough this aspect is not a very decisive factor in the design and layout of B waste cells, thermalmodels were created to check that the maximum temperature was well below 70°C. These models didnot take into account the favourable effect of ventilation, so that the design is independent of thechoice of management and in particular of the duration of ventilation after disposal. The mainhypotheses adopted for these thermal dimensioning studies are the same as for the thermaldimensioning of C waste cells (see section 5.2), i.e. mainly heat transfer by conduction and radiation,neighbouring cells simultaneously filled with the same exothermic packages and an initial rocktemperature of 22°C.The models show that, for packages disposed of at 10 years of age, the maximum temperature in thecell always remains below 70°C and drops back below 50°C at the end of about a century.Temperature Température (°C) (C°)Température du béton de colisage entre 0 et 1000 ans70B5.2 Colis Package B5,260504030200 100 200 300 400 500 600 700 800 900 1000Nombre Number d'années of years aprés after la mise disposal en stockageFigure 5.1.18Temperature in a cell of B5 .2 type packages placed at 10 years, without takingventilation into accountVentilation helps restrict heating in the cell (before and after closure). Ventilated air with a flow rateof 3m 3 /s can remove 80 to 90% of the heat released by B5 packages. Thus the maximum temperaturefor these packages could be permanently kept below 50°C by ventilating the cell for approximately 25years 70 .5.1.3.5 Mechanical dimensioning of the cell• Dimensioning of the cell ground support and liningThe mechanical dimensioning of the cells consists mainly in defining the ground support and thelining in the main section. The ground support is dimensioned so as to ensure the safety of theconstruction site over a maximum period of a year. The lining is dimensioned so as to ensure itsmechanical stability over a period of at least a century, in accordance with usage for civil engineeringstructures such as road or rail tunnels [61].Thermal effects are limited to a few cells.The studies further show that seismic resistance is not a major design factor [57].70Without ventilation, the heat builds up in the terrain near the cell, whereas ventilation removes it outside for good. Consequently, aftershutting down the ventilation, the temperature still remains below what it would have been without a ventilation phase.DOSSIER 2005 ARGILE -ARCHITECTURE AND MANAGEMENT OF A GEOLOGICAL DISPOSAL SYSTEM177/495