Tome Architecture and management of a geological repository - Andra

7 - Spent fuel repository zoneSweden opted for the "KBS-3" copper canister design back in the 1980s. Both SKB in Sweden andPosiva in Finland use this same reference for their repository studies in a granite medium (Figure7.2.4).Figure 7.2.4 The Swedish KBS-3 spent fuel design (SKB data [58])The issues concerning the canister’s feasibility have essentially dealt with its manufacturing and thewelding techniques to be used on the copper envelope. These issues have been covered by anextensive research programme which has demonstrated the possibility of manufacturing and weldingthe canisters (cf. § 7.3.3) [55].Furthermore full-scale experiments are being conducted to test the main elements of the KBS-3 designin the Äspö underground laboratory (Hard Rock Laboratory) in Sweden.The swelling engineered barrier placed around the disposal package contributes to maintainingcompatible chemical environment conditions with the thermo-dynamic stability range of canistercopper. In addition, the swelling clay engineered barrier provides mechanical stability for the disposalcell. Its contribution as chemical buffer affects both the water arriving from the granite and the waterfrom the handling drifts. The possible short and long-term chemical interactions with the canisters aretaken into consideration when formulating the engineered barrier.From a thermal viewpoint, the management of the evolution of the copper canister and the engineeredbarrier imply that temperature of the canister surface must not exceed 100°C. This calls for the spentfuel to be stored on surface prior to disposal and for an appropriate dimensioning of disposal modulein terms of distance between cells and of spacing between handling drifts (cf. § 7.4 and 7.5).Looking at the granite hydro-geochemical characteristics and their long-term evolution, it must bepoint out that copper canister dimensioning in Sweden is based on conditions that are in principlemore restrictive (with glacial context) than those likely to prevail in France.Lastly the requirements of canister durability could be lower, in the case of certain granite sites thathave more performing properties than those considered generically. The adaptation of the canisterdesign could then be based on the studies conducted by the Spanish agency ENRESA that aims toplace spent fuel in durable steel canisters in the disposal cells for several millennia (Figure 7.2.1).Dossier 2005 granite - ARCHITECTURE AND MANAGEMENT OF A GEOLOGICAL REPOSITORY202/228