DISPOSAL OF SPENT FUEL FROM GERMAN NUCLEAR POWER PLANTS

The "direct disposal of spent fuel" as a part of the current German reference concept was developed as an alternative to spent fuel reprocessing and vitrified HLW disposal. The technical facilities necessary for the implementation of this part of the reference concept, the so called POLLUX concept, i.e. interim storage buildings for casks containing spent fuel, a pilot conditioning facility, and a special cask "POLLUX" for final disposal have been built. With view to a geological salt formation all handling procedures for the direct disposal of spent fuel were tested aboveground in full-scale test facilities. To optimise the reference concept, all operational steps have been reviewed for possible improvements. The two additional concepts for the direct disposal of SF are the BSK 3 concept and the DIREGT concept. Both concepts rely on borehole emplacement technology, vertical boreholes for the BSK 3 concept und horizontal boreholes for the DIREGT concept. Supported by the EU and the German Federal Ministry of Economics and Technology (BMWi), DBE TECHNOLOGY built an aboveground full-scale test facility to simulate all relevant handling procedures for the BSK 3 disposal concept. GNS (Company for Nuclear Service), representing the German utilities, provided the main components and its know-how concerning cask design and manufacturing. The test program was concluded recently after more than 1.000 emplacement operations had been performed successfully. The BSK 3 emplacement system in total comprises an emplacement device, a borehole lock, a transport cart, a transfer cask which will shuttle between the aboveground conditioning facility and the underground repository, and the BSK 3 canister itself, designed to contain the fuel rods of three PWR-fuel assemblies with a total of about 1.6 tHM. The BSK 3 concept simplifies the operation of the repository because the handling procedures and techniques can also be applied for the disposal of reprocessing residues. In addition to this, the feasibility of the direct disposal of transport and storage casks, the so-called "DIREGT concept", is being investigated. The implementation of this concept would avoid the necessity to separate fuel rods from structural parts and to procure custom-made final disposal casks. All investigations and studies performed so far support the feasibility of direct disposal of spent fuel in multipurpose casks as today used for transport and storage. Both additional concepts, BSK 3 and DIREGT, are expected to simplify disposal processes and to reduce operational risk without any compromise in long-term radiological safety aspects.