Concept of a final storage of heat releasing radioactive wastes in clay stone in Germany

According to the German reference ultimate disposal concept, heat releasing radioactive wastes from nuclear power stations permanently are to be stored in a salt formation maintenance-free and non-recoverable. In the context of investigations on the use of alternative host rocks a concept for an ultimate waste disposal in clay stone was developed. All substantial aspects for the design, construction, operation and decommissioning were considered. The storage in 50 m deep boreholes in a mine with a depth of 350 m appears most appropriate. The final disposal in clay formations requires a substantial development of all pit areas with steel arches or spray concrete. Due to the smaller maximally permissible temperature in the filling material (bentonite), the floor space requirements for the final disposal site will be about five times larger. A period of more than one hundred years between exploration and decommissioning is estimated.