Hypothetical measures on high-level radioactive waste from the perspective of extended interim storage and final disposal

The site selection for a repository for high-level radioactive waste (HLW) will take longer than the currently authorised period of 40 years for interim storage sites in Germany. Extension of this period could necessitate additional handling or measures, such as treatments of HLW. This might have an impact on radionuclide mobility in the final repository. Therefore, BASE initiated a research project that studied the behaviour of HLW in interim storage was studied for causes of degradation, effects and consequences and possible treatments, performed by GRS gGmbH. There are currently no indications for mandatory measures during the authorized period and beyond, but some hypothetical treatments were identified. These treatments were evaluated with regard to their impact on interim storage, radiation exposure for personal, manageability and radionuclide mobility in repositories. Measures include, for example, heating and earlier removal from interim storage for conditioning. Even though technical feasibility was not part of the study, it seems clear that with any of the identified measures, higher radiation doses would have to be expected for the personnel. The impact of these measures on radionuclide mobility in the repository is assessed to be low. However, a more quantitative assessment of the impact of hypothetical treatments appears only feasible when a repository concept including waste acceptance criteria is fixed, which is not the case at the time of the study.