Differences in technical concepts for direct disposal of spent fuel and for disposal of high-level waste (HLW) from reprocessing are discussed. The preferred emplacement sites for spent-fuel elements are drifts instead of boreholes, which are used for vitrified HLW. The nuclide inventories of uranium and plutonium are considerably higher with direct disposal. The impact of these conceptual differences on the long-term safety of a repository in a salt formation is investigated.

The deterministically calculated radiation exposures for direct disposal and for disposal of reprocessed waste are both within the limits of the German licensing criterion. Furthermore, the differences in the radiation exposures are low, so from this point of view, neither concept is preferable. This result is surprising because the higher inventories of uranium and plutonium in the concept of direct disposal have a negligible influence on radiation exposure. It is shown that the layout temperature of a repository is a parameter influencing long-term safety, where higher layout temperatures are favorable.