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Materials Science at Oregon State University

Understanding Microstructure -Processing Relationships in Metallic Nuclear Fuels

Date: Thursday, Nov 15th
Presenter: Dr. Liz Kautz, Pacific Northwest National Laboratory

Abstract


Microstructure and chemistry of nuclear reactor core materials have a major influence on material performance, including mechanical and thermal properties, corrosion resistance, and irradiation stability. Therefore, it is essential to thoroughly understand processing required to obtain microstructures that yield desired properties, and thus in-pile performance for materials currently under development for application in nuclear reactors. The work presented here will be focused on a metallic nuclear fuel system (uranium alloyed with molybdenum), and characterization efforts that have enabled improved understanding of microstructure-processing relationships. The low-enriched uranium fuel system studied here is a candidate fuel for replacing currently used high enriched uranium fuels in research reactors and radioisotope facilities worldwide. The conversion from high to low enriched uranium fuel is needed to minimize proliferation risk associated with continued handling and operation of with highly-enriched uranium. Characterization efforts performed employ a variety of experimental techniques (scanning electron and focused ion beam microscopy, atom probe tomography, and transmission electron microscopy) to address the overarching goal of improving microstructure-processing relationships necessary for fuel qualification. We find that fuel chemistry and annealing parameters (time, temperature) impact grain boundary composition and structure, and subsequent phase transformation kinetics. Further, we demonstrate the applicability of atom probe tomography for nanoscale spatially resolved isotopic mapping of uranium across various microstructural features. Our results indicate a uranium carbide phase is formed during the casting process (and not retained from feedstock materials). The broader implications of this work are in understanding impact of impurity elements on phase transformation mechanisms and kinetics, and the applicability of atom probe tomography for nanoscale spatially resolved mapping of uranium isotopes. This work highlights the importance of leveraging multi-length scale characterization methods for improved understanding of microstructure-processing relationships, specifically for nuclear fuel cycle applications.

Bio:
Post Doctorate Research Associate – Pacific Northwest National Laboratory (2018-present)
Ph.D. Intern – Pacific Northwest National Laboratory (2017-2018)
Ph.D. – Materials Engineering, Rensselaer Polytechnic Institute (2014-2018)
Thesis title: Multi-Length scale Microstructure-Processing Characterization of Uranium-Molybdenum Alloys
M.S. - Materials Engineering, Rensselaer Polytechnic Institute (2010-2014, part-time)
Thesis title: Development of CCT Diagrams of Zr-Nb Alloy Phase Transformations within the Kolmogorov-Johnson-Mehl-Avrami Framework
Materials Engineer – Knolls Atomic Power Laboratory (2010-2014)
B.S. – Materials Engineering, Rensselaer Polytechnic Institute (2006-2010)

Research interests:
materials for nuclear fuel cycle applications, metallurgy, microstructure characterization, phase transformation kinetics, atom probe tomography, image processing, computer vision and machine learning