Architecture and management of a geological repository - Andra

4 – Waste disposal PackagesThe principle for handling the disposal containers in the cell was chosen for its consistency with theobjective of minimising the cell section and limiting the voids. Crane and gantry crane handling wasthus discarded, for it would require an area in the upper part of the cell that could not then be used fordisposal. The principle adopted is gripping the bottom using a type of fork-lift truck (seesection 9.3.2), which implies the needs for designing openings in the base of the container.Figure 4.1.2Standard disposal container (illustration for B2 reference package)• Variant on the possibility of calling on the retention ability of concrete in the wastedisposal packageA variant to this container has also been studied, which would call on the long term retention ability ofthe disposal package concrete (see § 4.1.1.3.). This variant only concerns primary waste packages thatdo not release gaseous elements (hydrogen in particular).This variant would thus serve to delay the migration of radionuclides during a very long period (scaleof several thousands of years). To achieve this, low permeability and a low diffusion coefficient atpackage scale are necessary, as well as long-term mechanical integrity. This leads to the quest for acompact concrete (low porosity). Low porosity limits both dissolved radionuclide transportation andconcrete degradation. Concrete degradation is reduced even more as it is difficult for the water and thedissolved species to move through it.One possible method of producing this variant (Figure 4.1.3) is to include a pre-fabricated body withhousings adjusted to the size of the primary packages, as for the standard package. However, the prefabricatedlid of the standard package is replaced by lids (or plugs) poured into each individualhousing once the primary packages are in place.The performance of the long-term disposal container are not only based on the thickness andperformances of the concrete used, but also on the quality of the connection between the body and thepoured lid. From this latter point of view, the adoption of small lids sized to each housing (diameter inthe order of 600 mm) could limit the problems of recovery and fissuring.The dimensions and weight of this variant are similar to a standard package.DOSSIER 2005 ARGILE -ARCHITECTURE AND MANAGEMENT OF A GEOLOGICAL DISPOSAL SYSTEM113/495