Architecture and management of a geological repository - Andra

4 – Waste disposal Packages4.1.5.7 Evolution of pH in a disposal situationThe choice of materials and development of the formulations presented above means that a target pHfor fresh concrete can be set at 13, which will rapidly fall to around 12.5 once the concrete hasmatured. Then, depending on the evolution of the concrete and its chemical breakdown, particularlyby hydrolysis, the pH will fall very slowly to a pH of about 10.5 in degraded state [48].4.1.6 Manufacturing techniquesThis section presents manufacturing techniques, in the factory and in the surface of installation ofrepository, selected for standard disposal packages on the one hand and the variant investigatingimproved retention capacity [41] on the other.These techniques were implemented to produce scale 1 demonstration containers with artificialprimary packages. The work was carried out jointly by Andra and the CEA in 2004 and 2005. For thestandard container, two variants have been produced (fibrous reinforced body, and fibrous nonreinforcedbody) based on B2.1 primary waste packages. For the variant with increased retentioncapacity, the container with prefabricated body and cast lid for primary packages B5.2 were produced.The manufacturing processes presented here are based on these demonstration models.Measurement and testing programmes carried out on manufactured objects made it possible to monitorthe evolution of the concrete used at a young age and to evaluate the performance of the container - lidbonds as well as the consequences of a package falling or being dropped.4.1.6.1 Manufacture of standard prefabricated disposal packages• General manufacturing principlesThe principle for manufacturing standard packages consists of maximising the number of stagesinvolved in a non-irradiating context, so that the quality of manufacture can be checked as simply aspossible and manufacturing costs optimised.Two types of elements are prefabricated in the factory in a non-irradiating context: bodies and lids.The other manufacturing operations are performed in irradiation cells:- loading primary packages;- closing disposal packages (by concreting joints or cementitious material);- maturing the body/lid closure seal in buffer storage (for 28 days);- package inspection before emplacement in the waste disposal cell.• Prefabrication process for lids and bodiesThe lids and bodies are prefabricated in a special unit including a concrete plant and a production shopfor managing the process, its control and repeatability.Manufacturing operations consist of moulding the body and lid, then after about 24 hours ofprestorage in the moulds, they are stripped and the objects cured, following application of a concretecuring product. Figure 4.1.7 presents the steel moulds produced for standard container demonstrationmodels.DOSSIER 2005 ARGILE -ARCHITECTURE AND MANAGEMENT OF A GEOLOGICAL DISPOSAL SYSTEM124/495