THE UNIVERSITY OF MANCHESTER Investigating Effect of Clay Composition on Safety Function Performance in a Geological Disposal Facility (GDF) A thesis submitted to the University of Manchester for the degree of Doctor of Philosophy in the Faculty of Science and Engineering 25th of September 2018 Adam Peter Sims School of Chemistry 49 Table of Contents Table of Contents.............................................................................................................2 Table of Figures................................................................................................................8 Table of Tables................................................................................................................15 Commonly used Abbreviations.......................................................................................17 Abstract............................................…............….............................................................19 Declaration of Work.................................................................................................…....20 Copyright Statement....................................................................................................…21 Acknowledgements.......................................................................…............................…22 About the Author............................................................................................................23 1. Introduction and Thesis content ......................................................................... 24 1.1. Project Significance .............................................................................................. 24 1.2. Aims and Objectives ............................................................................................. 27 1.3. Thesis Structure ................................................................................................... 29 1.4. Papers Submitted and Collaborators ................................................................... 32 1.5. Conferences, external work, and user facilities visited ....................................... 33 1.5.1. Conferences (presentations and posters) ..................................................... 33 1.5.2. External work ................................................................................................ 34 1.5.3. User Facilities ................................................................................................ 34 1.6. References ............................................................................................................ 35 2. Effects of Composition, Radiation Environment, and Corrosion Products on Performance of an Engineered Clay Barrier ............................................................. 38 2.1. The Nuclear Waste Story ..................................................................................... 38 2.1.1. The Nuclear Fuel Cycle .................................................................................. 39 2.1.2. UK Nuclear Legacy ......................................................................................... 42 2.1.3. Current Radioactive waste Storage .............................................................. 44 2.1.4. Geological Disposal ....................................................................................... 45 2.2. Engineered Clay Barrier ....................................................................................... 50 2.2.1. Clay Minerals ................................................................................................. 50 2.2.2. Smectites ....................................................................................................... 52 2 2.2.3. Bentonite ....................................................................................................... 53 2.2.4. Montmorillonite, Nontronite and Beidellite ................................................. 54 2.2.5. Colloids .......................................................................................................... 55 2.3. Challenges from heat generating HLW in a geological disposal facility .............. 55 2.3.1. Heating .......................................................................................................... 56 2.3.2. Irradiation ...................................................................................................... 57 2.3.3. Groundwater Infiltration ............................................................................... 59 2.3.4. Corrosion products ........................................................................................ 66 2.4. References ............................................................................................................ 66 3. Materials and Methods ....................................................................................... 84 3.1. Materials .............................................................................................................. 84 3.1.1. Clay Source Repository Clays ........................................................................ 84 3.1.2. Chemicals ...................................................................................................... 88 3.2. Methods ............................................................................................................... 88 3.2.1. Size Fractionation .......................................................................................... 88 3.2.2. Homoionisation ............................................................................................. 88 3.2.3. Clay Pellets .................................................................................................... 89 3.2.4. Heating .......................................................................................................... 89 3.2.5. γ-irradiation ................................................................................................... 89 3.2.6. α-irradiation .................................................................................................. 90 3.2.7. Colloidal Suspensions .................................................................................... 92 3.2.8. Sorption Experiments .................................................................................... 92 3.3. Clay Characterisation ........................................................................................... 94 3.3.1. Major Element Analysis................................................................................. 94 3.3.2. X-ray Diffraction (XRD) .................................................................................. 94 3.3.3. Infra-red Spectroscopy (IR) ........................................................................... 96 3 3.3.4 Cation Exchange Capacity (CEC), Sorption Properties, and Extractable Fe2+ Measurements ........................................................................................................ 97 3.3.5. Electron Paramagnetic Resonance spectroscopy (EPR) ............................... 99 3.3.6. X-ray Computed Tomography (XCT) ........................................................... 100 3.3.7. Colloidal Measurements ............................................................................. 102 3.3.8. Synchrotron Measurements ....................................................................... 104 3.4. Safety .................................................................................................................. 121 3.4.1. Laboratory Safety ........................................................................................ 121 3.4.2. Radiological Hazards ................................................................................... 121 3.4.3. Safety Courses ............................................................................................. 121 3.5. References .......................................................................................................... 122 4. Molecular- to meso-scale effects of heat and subsquent gamma radiation on engineered clay barrier performance for radioactive waste disposal ..................... 129 4.1 Abstract ............................................................................................................... 130 4.2. Introduction ....................................................................................................... 131 4.2.1. Effect of heating on clay performance ....................................................... 133 4.2.2. Effect of γ-irradiation on clay performance ................................................ 137 4.3. Methods and Materials ...................................................................................... 142 4.3.1. Clay preparation .......................................................................................... 142 4.3.2. Heat treatment and irradiation experiments ............................................. 142 4.3.3. Clay characterisation before and after heat treatment and irradiation .... 143 4.4. Results ................................................................................................................ 146 4.4.1. Clay chemical composition and exchangeable cations ............................... 146 4.4.2. Combined effects of heat and γ-radiation on clay structure ...................... 147 4.4.3. Effect of γ-irradiation on CEC and extractable Fe2+ .................................... 150 4.4.4. EXAFS