For nuclear facilities, external hazards are major contributors to the overall risk. Due to global warming, the frequency and intensity of certain types of external hazards may change. This holds, in particular, for hydrological and meteorological hazards. Therefore, GRS assess the climatic changes to be expected in Central Europe over the coming decades and their effects on the safety of nuclear power plants (NPPS), interim storage facilities and repositories for nuclear waste (during their operation phase) in the framework of the research project “Einfluss des Klimawandels auf die Sicherheit kerntechnischer Anlagen” (KlimakA) funded by BASE.

At the beginning of the project, a literature review on climate projections for Central Europe has been performed. The focus of this review was on information regarding extreme events with low exceedance frequencies, because this type of events is most relevant from a safety point of view. Depending on the facilities under consideration different time horizons are of interest: While for European NPPs the focus is on the next 60 to 80 years, for interim storage facilities and repositories longer time scales, up to well into the 22^nd century, are of interest. The study led to the following insights: (i) Climate projections are subject to large uncertainties. (ii) Evaluations with respect to events with low exceedance probabilities are scarce. (iii) Projections for changes beyond the current century are almost non-existent. (iv) With the exception of temperature increase, changes of hydrological and meteorological effects due to climate change will be limited for most central European countries.

Based on an evaluation of the worldwide NPP operating experience, a review of the design of European NPPs with respect to external hazards and considering the WENRA requirement to protect NPPs against hazards with return periods of 10.000 years, there is currently no indication of a major increase of the overall risk due to climate change. Nevertheless, operational challenges may arise. Hazards predominantly contributing to safety related effects are lightning strikes, high winds, biological hazards, low temperatures, and flooding events.

As interim storage facilities are less dependent on active systems than NPPs, their safety will probably be even less affected by climate change. One caveat being that climate projections beyond 2100 are scares and depend on uncertain assumptions. But as the pertinent design requirements for interim storage facilities are similarly high as those for NPPs, a high level of robustness of interim storage facilities can be expected. Similar considerations hold for the surface installations of repositories which will be assessed in the next step of KlimakA.

How to cite: Thuma, G. and Strack, C.: Climate Change in Central Europe and its Effects on External Hazards for Nuclear Facilities, Third interdisciplinary research symposium on the safety of nuclear disposal practices, Berlin, Germany, 17–19 Sep 2025, safeND2025-3, https://doi.org/10.5194/safend2025-3, 2025.

Over the assessment period of one million years, a repository for high-level radioactive waste (HAW) will be influenced by a multitude of processes and developments that must be considered when designing the repository. One such development is the climate, whose influences are highly dynamic and complex. To address these challenges, further research is required for global climate modelling using “Earth system Models of Intermediate Complexity” (EMICS) and in far-field modelling of potential repository sites in Germany. In this work far-field groundwater models are set up to estimate climate and parameter uncertainties to characterise and document the effects, and to show how or to what extent these uncertainties can be reduced in accordance with the requirements of EndlSiUntV §11.

The climatic states most relevant to the radionuclide transport in the far-field were identified and modelled using different boundary conditions. Groundwater models were set up and run for temperate climate, glaciation, permafrost, the presence of erosion valleys and sea level rise. A generic geological model from previous projects was used as the basis for modelling a potential repository site in claystone (Reinhold et al. 2013). The flow and transport processes of advection, density-driven flow, dispersion, diffusion, sorption and decay were implemented using the code “distributed density-driven flow (d³f++)” (Schneider et al. 2023, Fein 2004, Fein & Schneider 1999). The pollutant transport from the repository into the surrounding geological layers is modelled and evaluated at observation points. In addition, the mass integrals of the various model units are used to analyse the mass flow out of the host rock according to §4 section 5 of the EndlSiAnfV.

Simulations are carried out for different climate states and parameter variations in order to quantify their influence on the radionuclide distribution in the far-field. The results show a low influence of the climatic states and a significant influence of the diffusion as the primary transport process in the clay rock and the sorption as a strong retarding process. Only for low diffusion coefficients the hydraulic gradient affect the transport velocities. Site selection must be preceded by sufficiently good exploration to determine the rock properties as well as possible in order to be able to provide a robust safety case for the repository in the future.

References

Bundesministerium für Umwelt, Naturschutz, und nukleare Sicherheit (BMUV) (2020): Endlagersicherheitsanforderungsverordnung - EndlSiAnfV. BGBl. I S. 2094.

Bundesministerium für Umwelt, Naturschutz, und nukleare Sicherheit (BMUV) (2020): Endlagersicherheitsuntersuchungsverordnung - EndlSiUntV. BGBl. I S. 2094, 2103.

Fein, Eckard; Schneider, Anke (1999): d3f – Ein Programmpaket zur Modellierung von Dichteströmungen. Abschlussbericht. GRS-139. Braunschweig.

Reinhold, Klaus; Jahn, Steffen; Kühnlenz, Tatjana, Ptock, Lennart, Sönnke, Jürgen (2013): Methodenentwicklung und Anwendung eines Sicherheitsnachweiskonzeptes für einen generischen HAW-Endlagerstandort im Tonstein (AnSichT). Endlagerstandortmodell Nord (AnSichT) - Teil I: Beschreibung des geologischen Endlagerstandortmodells. Zwischenbericht. BGR. Hannover.

Schneider, Anke; Conen, Niklas Paul; Gehrke, Anne; Hilbert, Julian; Knodel, Markus M.; Kröhn, Klaus-Peter et al. (2023): HYMNE - hydrogeological modelling at a regional scale. GRS-750. Braunschweig.

How to cite: Johnen, M., Flügge, J., Fischer-Appelt, K., Charlier, F., Wolf, J., and Horenburg, P.: What matters more: Climate or parameters? A closer look at uncertainties in groundwater modelling, Third interdisciplinary research symposium on the safety of nuclear disposal practices, Berlin, Germany, 17–19 Sep 2025, safeND2025-79, https://doi.org/10.5194/safend2025-79, 2025.

The strategic study "CLIMATE: Impact of Climate Change on Nuclear Waste Management" is part of the European Partnership on Radioactive Waste Management (EURAD-2) and runs from October 2024 to September 2026.

The primary objective of this study is to identify knowledge gaps and provide recommendations for future research on the impact of climate change on radioactive waste management (RWM) facilities and sites across Europe. CLIMATE addresses all types of waste and storage systems (low level to high level waste; surface to deep storage). The entire lifetime of the disposal facility will be considered, i.e.,  construction, operation, as well as long-term post-closure phases, while pre-disposal facilities will also be included. A secondary goal of CLIMATE is to conduct a comprehensive assessment of existing regulatory and institutional frameworks on climate change impacts on RWM facilities, identifying gaps and needs while offering recommendations for future actions. Furthermore, CLIMATE aims to foster collaboration with civil society and stakeholders, by integrating societal concerns and insights into the development of climate resilience strategies for nuclear waste management and emphasising the importance of transparent communication as well as stakeholder involvement in the research and implementation process.

Short-term climate scenarios that may impact construction and operational RWM phases include especially extreme events such as extreme precipitation, which can lead to severe floods and landslides, extreme storm events or temperature increases with subsequent higher wildfire risk.

Long-term climate scenarios, which are relevant for the post-closure phase and which could compromise the integrity of radioactive waste repositories over time, include mainly changes in temperature conditions (global warming and global cooling including permafrost development and ice sheet advances), the geomorphological evolution of the region, sea level changes and hydrogeological shifts.

Assessments of these scenarios and their safety relevance are being conducted based on selected cases representing diverse European climate zones as well as different facilities (pre-disposal/processing vs. final disposal) and waste types (low-/intermediate vs. high-level radioactive waste). In the next step, CLIMATE will also make a selection of natural analogues that represent expected/possible future climate conditions to improve safety assessments for the long-term containment of radioactive materials.

As part of the large EURAD-2 partnership, CLIMATE is challenged but mostly enriched by combining different perspectives of all involved actors: waste management organisations (WMO), research entities (RE) and technical support organisations (TSO) as well as civil society organisations. The outcomes of this strategic study will provide valuable recommendations for policymakers, regulators, and the scientific community, contributing to the development of safety-oriented and effective strategies for radioactive waste management in the context of short-term (decades and centuries) and long-term (millenia and longer) climate change.

How to cite: Peti, L., Beerten, K., Geisler-Roblin, A., Park, J., Strusińska-Correia, A., Montoya, V., Van Zweel, K., Vercelli, M., and Sainz-García, A. M.: Impact of Climate Change on Nuclear Waste Management, Third interdisciplinary research symposium on the safety of nuclear disposal practices, Berlin, Germany, 17–19 Sep 2025, safeND2025-52, https://doi.org/10.5194/safend2025-52, 2025.