Atomistic modeling of the solid-state chemistry of actinide materials by Lindsay C. Shuller

199 Pages·2010·5.42 MB·English

Atomistic modeling of the solid-state chemistry
of actinide materials
by
Lindsay C. Shuller

A dissertation submitted in partial fulfillment
of the requirements of the degree of
Doctor of Philosophy
(Materials Science and Engineering)
in The University of Michigan
2010

Doctoral Committee:
Professor Rodney C. Ewing, Co-Chair
Professor Udo Becker, Co-Chair
Professor Ronald F. Fleming
Professor John Kieffer
Assistant Professor Anton Van der Ven
Professor Peter C. Burns, University of Notre Dame
© Lindsay C. Shuller
2010
To my husband Blake
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Acknowledgements
I would like to start by thanking my husband, as of October 16th, Blake Nickles, for
his continuous love, patience, and support. He has stood by my side every step of this
process and made 200+ miles seem not so far. I also could not have kept my sanity
without the constant love and support of my family – Jan and Don Shuller, Susan Shuller
and Max Franz, Debbie and Steve Nickles, and Kristina, Patrick, and Alex Woodward.
They were able to provide inspiration to my work without fully understanding the subject
matter.
After nine years at Michigan, five of which I was a graduate student, I have met many
people without whom my experience would not be complete. I decided to remain at
Michigan for graduate school after working for one year as an undergraduate student in
Rod Ewing and Udo Becker’s group. I was given unpaired guidance as an undergraduate
researcher by my mentor, Frannie Skomurski. She taught me that research was fun and
provided constant encouragement and guidance as I began developing my thesis topic.
Frannie has continued to support me academically and personally as both a mentor and
friend.
My co-advisors, Rod Ewing and Udo Becker, have given me such a unique graduate
experience. They provided the academic foundation for truly interdisciplinary research
and encouraged me from the start to think creatively about science and problem solving.
With their excellent guidance and superior leadership, I have had the opportunity to assist
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with writing successful (and unsuccessful) grant proposals, presenting at conferences and
workshops, both nationally and internationally, and discussing science with some of the
brightest students, faculty, and researchers.
The rest of my dissertation committee has contributed significantly to, not only my
dissertation, but my development as a scientist. John Kieffer and Anton Van der Ven
have been some of my most influential teachers during my undergraduate and graduate
coursework. Ron Fleming and I have spent countless hours discussing the thorium-fuel
cycle – a shared passion. Peter Burns, from University of Notre Dame, has graciously
agreed to serve on my dissertation committee. I appreciate his guidance from an
experimental perspective. His insight into uranium and neptunium mineralogy has been
irrefutably essential to my research on Np-incorporation into uranyl phases.
Additionally, I have had the opportunity to get my hands “dirty” in his lab at Notre
Dame, where he has allowed me to contribute to ongoing experiments looking at the
corrosion of Np-doped UO . My colleagues at University of Notre Dame – Ginger
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Sigmon-Brown, Daniel Unruh, and Jen Szymanowski – provided valuable assistance
while I worked in their lab and made me feel like part of their research group.
I could never have completed paper work on time or as easily if it weren’t for the
support staff in Materials Science and Engineering (Renee Hilgendorf) and Geology
(Anne Hudon and Nancy Kingsbury). I would like to further thank Anne Hudon, without
whom I would never have figured out my fellowship and would probably have had lapses
in my health insurance. Furthermore, the level of computational support that I have
received in my time at Michigan will be untouched. I am forever grateful to Janine
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Taylor for being such a great computer doctor and to Mike Messina for helping on the
research side of computer issues.
I had the privilege to work with Eric Essene, Carl Henderson, and Anja Schleicher,
during my stint as a graduate assistant in the Central Campus Electron Microscopy
Analysis Lab (EMAL). I learned a tremendous amount from them about mineralogy and
microscopy.
I would like to thank Joanna Mirecki-Millunchick for giving me the opportunity to
teach two semesters as her assistant. It was an honor to work with someone who
obviously cares so much about her teaching. Additionally, I would like to thank Joanna
for including me in her pedagogical research team. I have learned so much about
teaching and pedagogical research from her and our colleague Tershia Pinder-Grover.
Many great friends provided interesting conversation and fun times during my years
in graduate school. My roommates – both human and canine – helped keep me sane and
provided loads of entertainment. Thanks to Kristen Parrish, Julie Sturza, Laura Povlich,
Chris Nelson, and Leo Arnaboldi-Becker. Special thanks goes to Devon Renock. He
was not only a lunch buddy, co-teacher, and lab-mate, but a great friend. And last, but
not least, my colleagues at Michigan, who provided endless conversation about science,
culture, and life – Subashis Biswas, Amy Bengston, Artur Deditius, Darius Dixon, Martin
Reich, Elizabeth Ferriss, Qiaona Hu, Maik Lang, Jie Lian, Veronique Pointeau, Zsolt
Rak, Chintalapalle Ramana, Sandra Rey, Rosa Sureda, Satoshi Utsunomiya, Jianwei
Wang, Fuxiang Zhang, Jiaming Zhang.
I would like to acknowledge the Office of Civilian and Radioactive Waste
Management Fellowship for three years of graduate support. Supplemental support was
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provided by U.S. Department of Energy Office of Basic Energy Sciences (Grant DE
FG02 06ER15783) and U.S. Department of Energy Nuclear Energy University Program
(Grant DE-AC07-05ID14517). I have also been able to interact with great colleagues as
part of the Materials Science of Actinides, an Energy Frontier Research Center funded by
the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under
Award Number DE-SC0001089. Computational resources were provided by the NSF-
NIRT grant (EAR-0403732)

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Table of Contents
Dedication .......................................................................................................................... ii 
Acknowledgements .......................................................................................................... iii 
List of Figures ................................................................................................................... xi 
List of Tables .................................................................................................................. xiv 
Abstract ........................................................................................................................... xvi 
Chapter 1 Introduction..................................................................................................... 1 
References ............................................................................................................... 12 
Publications and abstracts resulting from this dissertation ..................................... 15 
Publications and abstracts resulting from side-projects .......................................... 17 
Chapter 2 Thermodynamic properties of Th U O (0 < x < 1) based on quantum-
x 1-x 2
mechanical calculations and Monte-Carlo simulations ............................................... 19 
Abstract ................................................................................................................... 19 
Introduction ............................................................................................................. 20 
Methodology ........................................................................................................... 22 
Quantum-mechanical calculations ...................................................................... 23 
Generating interaction parameters ...................................................................... 24 
Monte-Carlo simulations .................................................................................... 28 
Structure analysis of quantum-mechanical calculations ......................................... 29 
Thermodynamic properties of mixing .................................................................... 32 
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Composition of natural and synthetic Th U O .................................................... 43 
x 1-x 2
Comparison with calorimetric measurements ......................................................... 45 
Implications for Th U O solid solutions ............................................................. 48 
x 1-x 2
References ............................................................................................................... 49 
Chapter 3 Atomistic calculations of the thermodynamic properties of mixing for
tetravalent metal dioxide solid solutions: (Zr,Th,Ce)O ............................................. 54 
2
Abstract ................................................................................................................... 54 
Introduction ............................................................................................................. 55 
Methods................................................................................................................... 56 
Results ..................................................................................................................... 57 
Discussion ............................................................................................................... 63 
Exsolution tendency ............................................................................................ 63 
Cation ordering and end-member stability ......................................................... 69 
Miscibility limit .................................................................................................. 73 
Conclusions ............................................................................................................. 76 
References ............................................................................................................... 77 
Chapter 4 Quantum-mechanical evaluation of Np-incorporation into studtite ........ 80 
Abstract ................................................................................................................... 80 
Introduction ............................................................................................................. 81 
Methods................................................................................................................... 85 
Quantum-mechanical calculations ...................................................................... 85 
Calculation of incorporation energies ................................................................. 87 
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Calculations of the thermodynamic properties of the (U6+,Np6+)-studtite solid
solution ...................................................................................................................... 89 
Results and Discussion ........................................................................................... 91 
Refined crystal structure ..................................................................................... 91 
Electronic structure of studtite ............................................................................ 96 
Electronic structure of (Np6+ U6+ )-studtite ............................................... 100 
0.25 0.75
Thermodynamics of Np-incorporation into studtite ......................................... 107 
Thermodynamic properties of the (U,Np)-studtite solid solution ..................... 113 
Concluding Remarks ............................................................................................. 118 
Appendix 1: Np6+-modified studtite ..................................................................... 118 
Appendix 2: Np5+-modified studtite ..................................................................... 120 
References ............................................................................................................. 122 
Chapter 5 Np-incorporation into uranyl phases: A quantum-mechanical evaluation
......................................................................................................................................... 128 
Abstract ................................................................................................................. 128 
Introduction ........................................................................................................... 129 
Boltwoodite: Occurrence and structure ................................................................ 132 
Computational Methodology ................................................................................ 134 
What is the meaning of the CASTEP energy? .................................................. 136 
Calculating incorporation energies ................................................................... 138 
Estimating the limit of Np-incorporation .......................................................... 141 
Results ................................................................................................................... 143 
Substitution mechanism I: Np5+ + H+ ↔ U6+ ................................................... 143 
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