(GRS-890) Application of Climate Modelling to Assess the Robustness of Safety Statements and Scenario Uncertainties for the Disposal of High-Level Radioactive Waste

Marc Johnen (GRS) Christine Kaufhold (PIK) Judith Flügge (GRS) A. Ganopolski (PIK), J. Wolf (GRS), P. Horenburg (GRS), K. Fischer-Appelt (ELS), F. Charlier (ELS)

Project code: STAFuE-21-4-Klei

This final report presents the results of the REDUKLIM project, which investigated the influence of future climate developments on the long-term safety of a deep geological repository for high-level radioactive waste. The project aimed to identify and reduce uncertainties in safety assessments by combining global climate modelling, regional groundwater simulations, and sensitivity analyses.
 

Key objectives and findings:

  • Climate Modelling: Using the Earth system model CLIMBER-X, plausible climate scenarios for the next one million years were constructed, considering both natural evolution and anthropogenic emission scenarios. Results suggest that intermediate emission scenarios could delay the onset of the next glaciation to 100,000 years, while high cumulative CO2 emissions may postpone it for nearly 200,000 years.
  • Impact on Biosphere Dose: Climate conditions strongly affect agricultural irrigation needs and, consequently, the mean additional effective annual dose for a representative person of the population. Warmer scenarios increase irrigation deficits and potential radiation doses, whereas colder scenarios significantly reduce radiation exposure.
  • Stylised Climate States: Derived from model outputs, six representative climate states (temperate, permafrost, glaciation, glaciation with permafrost, erosion valleys, and sea level rise) were implemented in groundwater models to assess their impact on repository safety.
  • Groundwater Modelling: Long-term simulations show that glaciation can increase hydraulic gradients and therefore accelerate the radionuclide transport from the repository and the host rock. Other climate states, such as permafrost or sea level rise, have comparatively minor effects.
  • Sensitivity Analysis: Among all parameters in the groundwater models, sorption and diffusion coefficients exert the greatest influence on radionuclide transport. With the sensitivity analysis it can be said that climate states play a secondary role compared to these material properties.


Climate evolution is relevant for long-term safety but less critical than uncertainties in host rock properties. The results provide valuable input for site selection and safety case development by illustrating extreme conditions and their potential impact. Sensitivity analysis proved to be an effective tool for uncertainty quantification and prioritisation of research needs. In this final report, the results from all work packages (WP) are presented in a short form of the interim reports.