Architecture and management of a geological repository - Andra

5 – Repository ModulesIn terms of time, the conditions which in the short term govern evacuation of the heat produced by thepackages are different from those characterising the thermal behaviour of the repository in the longerterm. In the short term, the cells are in fact thermally independent of each other, while in the longerterm (more than three centuries), the "overall" heating of the repository zone leads to thermal couplingbetween the various units.To deal with this problem, a 3D finite-elements model was produced on the basis of three "nested"models (see Figure 5.1.10). Each of the three models is characterised by its own validity range:- the overall model on the scale of the site,- the median model on the scale of the repository module,- the local module on the scale of the disposal cell.The overall model (kilometre scale) represents the geological medium from the surface down to adepth of 3,500 m. The thermo-physical properties of the various geological layers are taken intoaccount. This general model can be used to calculate temperature evolutions over a period of10,000 years at numerous points located more than 50 m from the disposal packages. Over a periodsuch as this, the heat given off by the packages has an influence over a distance of a kilometre and thevarious repository modules interact thermally with each other. This general model thus represents allthe repository modules and covers a lateral distance of 2,000 m around the repository.The median model is on the scale of the repository module (metre scale). Its geometricalrepresentation is less detailed than the local model but it does include the structures surrounding thecell (access drifts, seals, etc). The calculation is made by applying to the edges the limit conditionsobtained on the overall model.The local model allows a detailed representation of the various cell components with a high degree ofgeometrical precision (centimetre scale). It enables the temperature evolution to be evaluated for theimmediate environment of the cell for all types of packages in the repository. There are as many localmodels as there are exothermic type packages. This model is used by applying to the edges the limitconditions obtained on the previous median model. It represents all the cell components, the functionalclearances, the spacers and the access structures.Scale ofthe siteScale ofseveraldisposal cellsTemperaturesat the limits ofthe model aregiven by thelarger modelScale of onedisposal cellFigure 5.2.10"Nested" modelling principle usedDOSSIER 2005 ARGILE -ARCHITECTURE AND MANAGEMENT OF A GEOLOGICAL DISPOSAL SYSTEM205/495