Architecture and management of a geological repository - Andra

2 – General Description- some connecting drifts serve the construction worksites and are equipped with railway lines ortracks for plant mounted on tyres. They are designed for the transfer of worksite personnel, miningequipment, broken rocks and construction materials;- other drifts are for the transfer of disposal packages;- finally, some drifts are specifically dedicated to ventilation air return.If and when a decision is taken to close the repository modules, the connecting drifts and shafts aresealed.2.4.3.2 Repository zonesThe design of the repository zones is essentially the outcome of the strategy to give the repository amodular feature. By adopting the principle of modularity, the various repository zones concerned canbe made and operated in a gradual, flexible manner. This is the underlying principle for the creation ofrepository modules consisting of one or more disposal cells. The repository zones are also designedaccording to safety considerations and notably ventilation in case of fire. Finally, geotechnicalconsiderations have led to the engineered structures being spaced apart by a distance equivalent toapproximately five times their diameter to guarantee their mechanical stability.When a decision is taken to close the repository, the various components of the repository zone(disposal cells, access drifts and connecting drifts) are sealed by means of low-permeability, swellingclay plugs and backfilled with the excavation broken rocks from the argillite formation. This process isimplemented gradually in successive stages. In the long term, the seals fulfil a separating function inthe repository zone.In the B waste repository zone, a repository module consists of a single disposal cell served by anaccess drift oriented along the cell axis. The disposal cells dedicated to packages containing organicmatter are kept away from the other cells in order to limit the impact of chemical disturbance that maybe caused by alteration of this organic matter in the long term.Figure 2.4.10Organisation of the B waste repository zoneThe figure above illustrates the possibility of separating the repository zone into two sub-zonesaccording to whether they contain organic matter or not.DOSSIER 2005 ARGILE -ARCHITECTURE AND MANAGEMENT OF A GEOLOGICAL DISPOSAL SYSTEM66/495