Structural Geology and Geomechanics in Nuclear Waste Management

Course Description

Structural geology and geomechanics play a central role in the safe and sustainable management of nuclear waste, particularly where long-term mechanical stability and geological integrity must be ensured over timescales of thousands to millions of years. This course on Structural Geology and Geomechanics in Nuclear Waste Management provides a comprehensive understanding of how geological structures, stress regimes, and failure mechanisms influence the selection, design, and monitoring of nuclear waste repositories. With a strong emphasis on mechanical failure criteria – especially the Mohr–Coulomb failure model – the course links fundamental geological theory with applied engineering and regulatory practice.

The course begins by outlining the broader context of nuclear waste management and the rationale for geological disposal as the preferred long-term solution for high-level and long-lived radioactive waste. Key repository principles such as isolation, containment, and the use of engineered and natural barriers are introduced. Within this framework, structural geology is presented as a critical discipline, as faults, fractures, folds, and other deformation features directly influence rock strength, permeability, and long-term stability. Understanding these features is essential for evaluating whether a geological formation can safely host a repository without compromising containment or increasing the risk of contaminant migration.

Part of the course is dedicated to the principles of structural geology, with particular attention to the identification, mapping, and interpretation of geological structures in the subsurface. Geological structures are treated as dynamic elements whose evolution must be considered in long-term safety assessments, particularly in response to natural stresses, repository excavation, and thermally induced stresses resulting from radioactive decay.

Central to the course is the application of failure criteria, with the Mohr–Coulomb model serving as the primary analytical framework. The theoretical basis of this model is explored, including concepts of normal and shear stress, cohesion, internal friction, and stress envelopes. Practical examples and case studies demonstrate how laboratory-derived strength parameters are transferred to field-scale assessments and how uncertainties in material properties affect safety margins.

Building on this foundation, the course addresses site stability assessment and the determination of mechanical strength parameters in repository design. Particular emphasis is placed on the role of faults and fracture networks as zones of weakness or potential fluid pathways, and on the interaction between geological structures and engineered components such as tunnels, shafts, and waste canisters.

Monitoring and long-term observation form another key theme. Methods for detecting subsurface deformation, stress redistribution, and damage evolution – such as geodetic measurements and microseismic monitoring – are presented as essential tools for safety assessment, adaptive management, and regulatory compliance. 

Consequently, the course situates structural geological and geomechanical analysis within broader risk assessment and regulatory frameworks, demonstrating how structural geological data and failure criteria support safety cases and long-term decision-making in nuclear waste disposal.

Course Outline

1. Course Context: Structural Geology in Nuclear Waste Disposal (20 min)
Role of structural geology and geomechanics in ensuring long term mechanical stability and geological integrity of nuclear waste repositories over geological timescales.
2. Nuclear Waste Management and Geological Disposal Concept (40 min)
Overview of nuclear waste management, justification for geological disposal, and the long term safety challenges associated with high level and long lived radioactive waste.
3. Repository Safety Principles and Barrier Systems (40 min)
Introduction to isolation, containment, and engineered and natural barriers, and how geological conditions underpin repository performance.
4. Structural Geological Controls on Rock Mass Behavior (30 min)
Influence of faults, fractures, folds, and deformation features on rock strength, permeability, and long term stability relevant to repository siting.
5. Geological Structures, Stress Regimes, and Evolution (35 min)
Tectonic history, stress fields, and deformation processes, treating geological structures as dynamic elements relevant to long term safety assessments.
6. Identification and Interpretation of Subsurface Structures (30 min)
Principles of mapping and interpreting subsurface geological structures for site characterization and repository design.
7. Mechanical Failure Criteria and the Mohr–Coulomb Model (60 min)
Conceptual and theoretical basis of mechanical failure, with emphasis on the Mohr–Coulomb failure criterion and its key parameters.
8. From Laboratory Strength to Field Scale Assessment (45 min)
Transfer of laboratory derived strength parameters to field conditions, including uncertainty, scale effects, and implications for safety margins.
9. Site Stability, Faults, and Repository Engineering Interaction (60 min)
Assessment of site stability, role of faults and fracture networks as weaknesses or fluid pathways, and interaction between geological structures and engineered components.
10. Monitoring, Safety Cases, and Regulatory Integration (45 min)
Monitoring of deformation and stress evolution, and integration of structural geological and geomechanical analyses into safety cases, risk assessment, and regulatory decision making.

The class includes two coffee breaks of 15 minutes each plus an one hour lunch break and a 15 minute wrap-up.

Participants’ Profile

This course is designed for professionals and advanced students involved in the geological, mechanical, and safety aspects of nuclear waste management and underground repository systems. It is particularly suitable for:

•    Geoscientists and geologists (e.g. structural geology, engineering geology, hydrogeology) working on subsurface characterization, site assessment, or long term geological safety
•    Rock mechanics, geotechnical, and civil engineers involved in the design, analysis, or monitoring of underground excavations and repository structures
•    Professionals in nuclear waste management organizations responsible for site selection, repository design, performance assessment, or long term monitoring
•    Regulators, safety analysts, and technical advisors seeking a deeper understanding of how structural geology and failure criteria underpin safety cases and regulatory decision making.

The course is also appropriate for doctoral researchers and postgraduate students aiming to strengthen the link between structural geology theory and applied repository engineering.

Prerequisites

No formal prerequisites are required. However, participants are expected to have a basic academic or professional background in geoscience or engineering. Familiarity with fundamental geological concepts (such as rock types and geological structures) and basic mechanics concepts (such as stress and material strength) will support effective engagement with the course material. The course is not introductory in nature; it builds on existing knowledge and focuses on applied analysis, interpretation, and decision making in the context of long term nuclear waste disposal.

About the Instructor

Dr. Carlo Dietl I got his MSc in Geology/Paleontology in 1995 at the Technical University of Darmstadt (Germany). He later got his PhD in Geology in 2000 at University Heidelberg (Germany). During his PhD time he worked about pluton emplacement in the Mid German Crystalline High and the White-Inyo Range (California). Between 2002 and 2012  he worked as postdoc and assistant professor at the geo departments of the universities of Heidelberg, Stockholm (Sweden), Würzburg and Frankfurt/Main (both Germany) - still with a strong focus on pluton emplacement and ductile processes in the lower and middle continental crust, but now analogue modeling, in particular centrifuge experiments of diapirism and dyking played a more central role in my scientific work. From 2012 to 2020 he was appointed as project manager at Gesteinslabor Dr. Eberhard Jahns (Heilbad Heiligenstadt, Germany). It was at Gesteinslabor, where his interest in brittle processes grew and where he got in touch with the Swiss site selection process, due to Gesteinslabor taking part in several rock testing programs for the Swiss implementer in the search for an appropriate disposal site for nuclear waste - Nagra. Since 2020 he has worked as scientist at the research department of the German Federal Office for the Safety of Nuclear Waste Management (BASE) in Berlin. He is responsible for research carried out at the Grimsel Test Site (Swiss Alps), for numerical modeling projects, for CT image analysis and for permeability investigations.

His scientific interests are structural geology, geomechanics, analogue and numerical modeling of deformation processes, management of radioactive waste with a focus on final disposal of high-level nuclear waste and uranium mining and its residues as well as geothermal energy.