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Investigations of Nuclear Forensic Signatures in Uranium Bearing Materials

Meyers, Lisa A
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1380556939

Abstract Details

2013, PhD, University of Cincinnati, Arts and Sciences: Chemistry.
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 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.
Thomas Beck, Ph.D. (Committee Chair)
William Connick, Ph.D. (Committee Member)
Thomas Ridgway, Ph.D. (Committee Member)
Henry Spitz, Ph.D. (Committee Member)
Apryll Stalcup, Ph.D. (Committee Member)
116 p.
Chemistry
Nuclear Forensics; Radiochronometry; uranium; thorium; isotopic signatures; age dating

Recommended Citations

Citations

  • Meyers, L. A. (2013). Investigations of Nuclear Forensic Signatures in Uranium Bearing Materials [Doctoral dissertation, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1380556939

    APA Style (7th edition)

  • Meyers, Lisa. Investigations of Nuclear Forensic Signatures in Uranium Bearing Materials. 2013. University of Cincinnati, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1380556939.

    MLA Style (8th edition)

  • Meyers, Lisa. "Investigations of Nuclear Forensic Signatures in Uranium Bearing Materials." Doctoral dissertation, University of Cincinnati, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1380556939

    Chicago Manual of Style (17th edition)

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© 2013, all rights reserved.
This open access ETD is published by University of Cincinnati and OhioLINK.