CORROSION OF UO2 AND THERMODYNAMIC PROPERTIES OF SOLID SOLUTIONS IN THE ZIRCON GROUP by Elizabeth D. A. Ferriss A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy (Geology) in The University of Michigan 2009 Doctoral Committee: Associate Professor Udo Becker, Co-Chair Professor Rodney C Ewing, Co-Chair Professor Emeritus Eric J Essene Professor Youxue Zhang Assistant Professor Anton van der Ven © Elizabeth D. A. Ferriss 2009 ACKNOWLEDGMENTS First, thank you to my co-chairs Rod Ewing and Udo Becker. Also thanks to my co-authors Pat Brady, Charles Bryan, Eric Essene, and especially Kate Helean. I am grateful to my other committee members past and present: Youxue Zhang, Anton van der Ven, Lars Stixrude, and Kim Hayes. Also to my husband Mark, who provided a fabulous last name, abundant encouragement, and mad formatting skills. Peter van Keken and Eric Kneller taught me essentially everything I know about programming. Artur Deditius, Carl Henderson, and Eric Essene were particularly helpful with the EMPA/WDS and SEM/EDS work. Corey Lambert and Ted Huston were always patient and willing to help me with my latest project. I would not have gotten far at all without Anne Hudon and the rest of the office staff. Lynn Walter was wonderful in helping to get me settled in my first year. Two anonymous reviewers and Thomas Zack provided comments that lead to a substantial improvement in the manuscripts for Chapters 2 and 4. Thanks to Satoshi Utsunomiya and Edgar Buck for discussion about the applicability of TEM to the work described in Chapter 4. Edgar also hosted me for an internship at PNNL. Thanks to Charles Anderson (hi dad!) for the statistics work. Thank you also to my fellow students and friends, particularly Frannie Skomurski (U), Lindsay Shuller (Np), Qiaona Hu (“Joanna”), Monamie (Bhadra) and Sam Haines, the “Friday Night Coven”, Sarah Rilling, Darius Dixon, Subhashis ii Biswas, Cheryl Peyer, Chris Stefano, Devon Renock, J.P. Brandenburg, and Martin Reich. Financial support came in the form of fellowships from the Dept. of Geological Sciences (1st year), the U.S. Department of Energy Office for Civilian Radioactive Waste Management (2nd year), and the National Science Foundation (3rd- 5th years). This work was supported by the Office of Science and Technology and International (OST&I) of the Office of Civilian Radioactive Waste Management (DE- FE28-04RW12254) and NSF-NIRT (EAR-0403732). Many of the computations in Chapter 3 were performed on the University of Michigan Legato cluster (funded through National Science Foundation grant EAR-0651056 to Peter van Keken and Jeroen Ritsema). iii CONTENTS Acknowledgments............................................................................................................... ii List of Figures................................................................................................................... vii List of Tables .................................................................................................................... xii List of Appendices ........................................................................................................... xiv Abstract............................................................................................................................. xv CHAPTER 1. INTRODUCTION.................................................................................... 1 1.1. References................................................................................................................ 7 1.2. Publications and Abstracts Resulting from this Disssertation............................... 11 1.2a. Publications....................................................................................................... 11 1.2b. Conference Proceedings ................................................................................... 11 1.2c. Presentations ..................................................................................................... 12 CHAPTER 2. UO2 CORROSION IN AN IRON WASTE PACKAGE..................... 13 2.1. Abstract.................................................................................................................. 13 2.2. Introduction............................................................................................................ 14 2.3. Methods ................................................................................................................. 15 2.3a. Miniature steel waste packages......................................................................... 15 2.3b. Yucca Mountain process water......................................................................... 19 2.3c. Characterization of solids ................................................................................. 20 2.3d. Water chemistry................................................................................................ 22 2.4. Results.................................................................................................................... 23 2.4a. Fe speciation and pe-pH conditions.................................................................. 23 2.4b. Metal corrosion products .................................................................................. 25 2.4c. Corrosion of UO2 .............................................................................................. 31 iv 2.5. Discussion.............................................................................................................. 34 2.5a. Lowered redox conditions................................................................................. 34 2.5b. Kinetic hindrance of UO2 corrosion ................................................................. 37 2.5c. Implications for radionuclide release from waste packages ............................. 38 2.6. Conclusions............................................................................................................ 40 2.7. References.............................................................................................................. 41 CHAPTER 3. SIMULATION OF THERMODYNAMIC MIXING PROPERTIES OF ACTINIDE-CONTAINING ZIRCON SOLID-SOLUTIONS .. 48 3.1. Abstract.................................................................................................................. 48 3.2. Introduction............................................................................................................ 49 3.3. Zircon solid solutions in nature and experiments .................................................. 51 3.3a. Hf and rare earth elements ................................................................................ 52 3.3b. Actinides........................................................................................................... 54 3.4. Methods ................................................................................................................. 59 3.4a. Total-energy calculations.................................................................................. 61 3.4b. Fitting of Margules and interaction parameters................................................ 62 3.4c. Thermodynamic properties from Monte-Carlo simulations and subsequent thermodynamic integration........................................................................................ 65 3.5. Results.................................................................................................................... 67 3.6. Discussion.............................................................................................................. 73 3.6a. Miscibility trends and bonded radii .................................................................. 73 3.6b. Estimates of miscibility and end-member stability .......................................... 76 3.6c. Exsolution ......................................................................................................... 80 3.7. Conclusions............................................................................................................ 82 3.8. References.............................................................................................................. 84 CHAPTER 4. COMPUTATIONAL STUDY OF THE EFFECT OF PRESSURE ON THE TI-IN-ZIRCON GEOTHERMOMETER.................................................... 91 4.1. Abstract.................................................................................................................. 91 4.2. Introduction............................................................................................................ 92 v 4.3. Computational Methods......................................................................................... 95 4.3a. Quantum-mechanical total-energy calculations................................................ 95 4.3b. Evaluation of solid-solution mixing properties ................................................ 96 4.3c. Quantum mechanical treatment of representative compositions ...................... 96 4.3d. Calculation of cation-cation interaction parameters for solid solutions ........... 98 4.3e. Monte-Carlo simulation: determination of thermodynamic properties .......... 101 4.4. Results.................................................................................................................. 102 4.4a. Free energy comparison.................................................................................. 102 4.4b. Solid solutions ...............................................................................................