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Investigations of Nuclear Forensic Signatures in Uranium Bearing Materials a Dissertation Submitted to the Graduate School of the University of Cincinnati

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Investigations of Nuclear Forensic Signatures in Uranium Bearing Materials a Dissertation Submitted to the Graduate School of the University of Cincinnati Investigations of Nuclear Forensic Signatures in Uranium Bearing Materials A dissertation submitted to the Graduate School of the University of Cincinnati in partial fulfillment of the requirements for the degree of Doctor of Philosophy (Ph.D) In the Department of Chemistry Of the McMicken College of Arts and Sciences By Lisa Ann Meyers B.S. Ohio Northern University 2009 August 2013 Committee Chairs: Thomas Beck, Ph.D. Apryll Stalcup, Ph.D. i Abstract Nuclear forensics is a multidisciplinary science that uses a variety of analytical methods and tools to investigate the physical, chemical, elemental, and isotopic characteristics of nuclear and radiological material. A collection of these characteristics is called signatures that aids in determining how, where and when the material was manufactured. Radiological chronometry (i.e., age dating) is an important tool in nuclear forensics that uses several methods to determine the length of time that has elapsed since a material was last purified. For example, the “age” of a uranium-bearing material is determined by measuring the ingrowth of 230Th from its parent, 234U. A piece of scrap uranium metal bar buried in the dirt floor of an old, abandoned metal rolling mill was analyzed using multi-collector inductively coupled plasma mass spectroscopy (MC-ICP- MS). The mill rolled uranium rods in the 1940s and 1950s. The age of the metal bar was determined to be 61 years at the time of analysis using the 230Th/234U chronometer, which corresponds to a purification date of July 1950 ± 1.5 years. Radiochronometry was determined for three different types of uranium metal samples. The affects of different etching procedures were evaluated to determine whether etching procedures affect radiological age. The sample treated with a rigorous etching procedure (concentrated HNO3) had exhibited the most reliable radiological age while less rigorous etching (8M HNO3) yields a radiological age from 15 years to hundreds of years older than the known age. Any excess thorium on the surface of a uranium metal sample presents a bias in age determination and the sample will appear older than the true age. Although this research demonstrates the need for rigorous surface etching, a bias in ii the radiological age could have arisen if the uranium in the metal was heterogeneously distributed. The uranium isotopic composition of radiological samples can reveal whether the uranium is natural, depleted, or enriched and whether the material has ever been subjected to neutron irradiation or reprocessing. The signatures contained in samples of dirt collected at two different uranium metal processing facilities in the United States were evaluated to determine uranium isotopic composition and compare results with processes that were conducted at these sites. One site refined uranium and fabricated uranium metal ingots for fuel and targets and the other site rolled hot forged uranium and other metals into dimensional rods. Unique signatures were found that are consistent with the activities and processes conducted at each facility and establish confidence in using these characteristics to reveal the provenance of other materials that exhibit similar signatures. In this research, nuclear forensics signatures of a variety of different types of uranium bearing samples, including metals, soils, and ore deposits were determined. Radiochronometry, uranium, thorium, and plutonium isotopic analysis, and elemental composition of these materials were all analyzed. These characteristics, when evaluated alone or in combination, become signatures that may reveal how and when the material was fabricated. iii iv Acknowledgments None of my accomplishments would have been possible without a loving, strong, supporting, and encouraging group of people close by me. I would first like to thank my PhD committee (Dr. Beck, Dr. Ridgway, Dr. Connick, Dr. Spitz, and Dr. Stalcup) and the Department of Chemistry at UC for all of their support and guidance throughout this process. I would like to especially thank my co-advisors, Dr. Apryll Stalcup and Dr. Henry Spitz, who has helped me grow as both a scientist and a person. They have opened up many unique opportunities in my graduate school career that I wouldn’t have otherwise. I would like to thank Dr. LaMont and Dr. Glover for their mentorship and support. I would like to thank the past and present Stalcup and Spitz group for all their support and encouragement. I would like to thank Dr. Ross Williams for his expertise and assistance for my dissertation research at Lawrence Livermore National Laboratory, along with Dr. Kim Knight, Dr. Sarah Roberts, and Rachel Lindvall who helped me with instrumentation operations and/or ran analyses on my samples. I would like to thank Kim Carey for answering my random questions, working hard at scheduling my seminars, as well as providing help with anything I needed. I strongly believe that the department of chemistry wouldn’t be able to function without her. I would like to thank my undergraduate research advisor Dr. Celius and his wife Rachael, who always had faith in my future and accomplishments and have always been very supporting even throughout my time in graduate school. Finally, I would like to thank my family and friends for their daily love and support. This dissertation would not have been possible without all of you. Thank you. This work wouldn’t have been able to be accomplished without the help of funding from various places. I would like to thank the U.S. Department of Energy’s Nuclear Materials Information Program for funding this research. This work was part performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344, support by the U.S. Department of Homeland Security under Grant Award Number 2012-DN-130-NF0001-02, and the Nuclear Forensics Graduate Fellowship Program, which is sponsored by the U.S. Department of Homeland Security, Domestic Nuclear Detection Office and the U.S. Department of Defense, Defense Threat Reduction Agency. The views and conclusions contained in this document are those of the authors and should not be interpreted as necessarily representing the official policies, either expressed or implied, of the U.S. Department of Homeland Security. v Table of Contents Abstract............................................................................................................................... ii Acknowledgements..............................................................................................................v List of Tables ................................................................................................................... viii List of Figures.................................................................................................................... ix Chapter 1: Nuclear Forensics Signatures and Techniques ..................................................1 1.1 Introduction to Nuclear Forensics......................................................................1 1.2 Nuclear Forensic Signatures ..............................................................................2 1.2.1 Uranium and Thorium Isotopic Signatures.........................................2 1.2.2 Plutonium Isotopic Signatures ............................................................4 1.2.3 Radiochronometry...............................................................................5 1.3 Instrumentation Techniques...............................................................................6 1.3.1 Non-destructive Surface Characterization Techniques ......................6 1.3.1.1 Scanning Electron Microscopy (SEM) and Electron Dispersive Spectroscopy (EDS) ......................................................6 1.3.1.2 X-ray Diffraction (XRD) ....................................................8 1.3.2 Destructive Elemental Techniques ..................................................10 1.3.2.1 Inductive Coupled Plasma Mass Spectrometry (ICP-MS) 10 1.3.2.2 Multi-collector ICP-MS (MC-ICP-MS) ...........................12 1.3.2.3 Isotope Dilution Mass Spectrometry (IDMS)....................16 1.4 Actinide Separations .......................................................................................17 1.5 Research Focus ................................................................................................24 1.6 References........................................................................................................25 Chapter 2: Radiochronological Age of a Uranium Metal Sample from an Abandoned Facility ..............................................................................................................................29 2.1 Introduction......................................................................................................29 2.2 Experimental....................................................................................................31 2.2.1 Methods.............................................................................................31 vi 2.2.2 Sample preparation of soil ................................................................31 2.2.3 Radiochemical separation and purification chromatography of soil samples ......................................................................................................32 2.2.4 Sample preparation of uranium metal ..............................................34 2.2.5 Radiochemical separation and purification chromatography of
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