Using deep boreholes for disposal of high-level radioactive waste (HLRW) can take advantage of multiple geologic barriers as safety features. The great depth efficiently prolongs or hinders radionuclide transport and also impedes proliferation. Finally, there may be a time benefit for technical implementation and costs. The number of boreholes could be less than 100 for the volume of HLRW in Germany due to the phase-out from nuclear energy. Using a simplified, generic safety concept, minimum requirements for the diameter of boreholes and containers are derived. Furthermore the operational safety of emplacement, retrieval of waste and sealing of the boreholes is considered. Boreholes can be sealed quickly e.g. using the creep properties of salt rock formations. This concept is assessed for its compliance with the safety requirements of the German Federal Ministry for the Environment, Nature Conservation, Building and Nuclear Safety (BMUB) and the requirements and criteria for site selection defined by the German commission on "Storage of high-level radioactive waste ". In principle deep boreholes disposal (DBD) can show the safe containment of radionuclides by containment-providing rock zones (CPRZ). Further developments in concept, demonstration of technical feasibility and an assessment of operational and long-term safety of DBD are still necessary. The retrievability of HLRW is technically feasible based on today's knowledge, but recovery for 500 years after closure cannot be guaranteed for the whole period. For geological disposal of HLR W in deep boreholes to have a chance in Germany, its technical feasibility should be demonstrated and a detailed safety analysis of operational and long-term safety should be performed. There is currently no application in the oil and gas industry of deep boreholes with the anticipated large diameters. Therefore DBD needs active support in research, development and demonstration.
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