Architecture and management of a geological repository - Andra

4 – Waste disposal Packages4.1.3 Description and design of a standard containerThis section describes the design parameters for the solution adopted for the standard container ingreater detail. The disposal container presented here satisfies both the needs of a repository expressedpreviously and those of long-term storage, which is the waste management path studied by the CEA. Ithas therefore been designed by joint CEA and Andra collaboration. The mechanical design and thecompatibility of the object with the handling processes are presented [41].4.1.3.1 DescriptionThe container body and lid are pre-fabricated in reinforced, concrete 27 which also containers as smallamont of fibres. The fibre content (25 to 30 kg/m 3 ) prevents heterogeneous fissuring of the concretefrom shrinking during curing; shrinking can then only be caused by micro-fissures spreadhomogenously, that will not weaken the object.To limit risks of corrosion and improve the mechanical durability of the container, stainless steel hasbeen adopted for the reinforcements and fibres. Note that in a repository situation, the very lowhumidity expected in the cells while oxidising conditions are prevalent would nevertheless limit therisk of corrosion of non- or low-alloy steels reinforcements and fibres or in steel casting for the fibres.The body is in high-performance concrete with 75 MPa compressive strength and the lid in 60 MPahigh-performance concrete. The lid consists of a plate placed on the inside sill of the side walls in thebody (Figure 4.1.5), with five bushings (1 central and 4 around the edge) to carry the bolts fixed in thebody (see below).To evacuate the hydrogen produced by the vast majority of the primary packages, vents can be addedto the top of the container body. These vents comprise a cylindrical opening reserved during the prefabricationof the container body and are located on the two opposing faces of the container, to allowthe hydrogen to be diffused outside the disposal package.A second hydrogen evacuation method is also taken into account in the container design, to ensurecompatibility with the long-term storage specifications. This involves diffusion through the concrete inthe lid. The result is a specific concrete being chosen for the lid with its thickness limited to 150 mm atthis stage. These specific lid characteristics make it permeable to hydrogen without the need to providevents for long-term storage 28To close the container, the lid is keyed mechanically to the body using a cementitious material pouredinto a groove formed between the body and the lid. Filling the lid bushings with the cementitiousmaterial seals the bolts to the lid. The sealed bolts help to unite lid and body and minimise the risk ofthe lid being torn off during a fall.2728Variants limiting the reinforcements, but with added fibre content have also been studied. A first variant thus consists of a fibrereinforcedbody with over 50 kg/m 3 fibre contact and a reinforced, lid containing a small amont of fibre. The over all dimensions, bodygeometry and reinforced lid remain unchanged. A second variant with no reinforcement would require a concrete lid thicker than150 mm, which is incompatible under current knowledge with hydrogen being evacuated through the concrete porosity (long-termstorage situation).At this stage in the studies, it is considered that the vents are blocked during storage and freed if necessary when the container enters therepository.DOSSIER 2005 ARGILE -ARCHITECTURE AND MANAGEMENT OF A GEOLOGICAL DISPOSAL SYSTEM116/495