Actinide and Lanthanide Materials III: Fuels
Program Organizers: Clarissa Yablinsky, Los Alamos National Laboratory; Ryan Stillwell, Lawrence Livermore National Laboratory; Kester Clarke, Colorado School of Mines; Clinique Brundidge, Naval Surface Warfare Center; Adam Farrow, Los Alamos National Laboratory; Curt Lavender, Battelle - Pacific Northwest National Laboratory; Douglas Burkes, Pacific Northwest National Laboratory

Tuesday 2:00 PM
October 1, 2019
Room: C120
Location: Oregon Convention Center

Session Chair: Clarissa Yablinsky, Los Alamos National Laboratory; Ryan Stillwell, Lawrence Livermore National Laboratory

2:00 PM  Invited
Constituent Redistribution and Lanthanide Migration in Neutron Irradiated Uranium Zirconium Fuel: Maria Okuniewski1; Jonova Thomas1; Walter Williams1; Lingfeng He2; Xiang Liu2; 1Purdue University; 2Idaho National Laboratory
    During in-pile irradiation of uranium zirconium (U-Zr) fuel, the major constituents of both U and Zr redistribute due to both thermal and concentration gradients that exist radially and axially within the fuel. The lanthanide fission products also exhibit specific segregation trends that occur both radially and locally within certain phases. Recent advances in characterization techniques now allow for a more comprehensive examination of these phenomena from both two dimensional and three dimensional perspectives. Electron microscopy, synchrotron techniques, and atom probe tomography results will be discussed in the context of U-Zr fuel redistribution behavior spanning the macroscopic to atomistic length scales.

2:30 PM  
Carbon Uptake during the Processing of Uranium: Kara Luitjohan1; Seth Imhoff1; 1Los Alamos National Laboratory
    The efficient manufacturing of metals often requires reuse and recycling. However, as metals are processed, they often degrade in quality through an increase in impurity concentration. Uranium, a highly reactive metal, is especially prone to increased impurity levels, particularly carbon. Common conditions encountered during uranium vacuum induction melting provide ample sources for carbon uptake by the metal, but the prevalence of a dominant mechanism is difficult to determine under full-scale processing. This study attempts to separate potential carbon uptake issues related to barrier coatings, gas transport, and native oxide integrity.

2:50 PM  
Influence of Divergency and Initiation Site on Kinetics of Cellular Growth and Coarsening in Aged U-Nb Alloys: Robert Hackenberg1; Megan Emigh1; Pallas Papin1; Ann Kelly1; Robert Forsyth1; Tim Tucker1; Kester Clarke2; 1Los Alamos National Laboratory; 2Colorado School of Mines
    Lamellar decomposition products result when U-Nb alloys are transformed between about 300C and the 647C monotectoid temperature. The kinetics of these cellular precipitation reactions are of interest since the resulting microstructures give undesirable properties. Detailed kinetic studies of these reactions were undertaken in U-Nb alloys isothermally transformed over a wide span of time and temperature. The volume fractions, growth rates, interlamellar spacings, and phase compositions of the discontinuous precipitation as well as the succeeding discontinuous coarsening reactions were measured. These results will be compared with theories of cellular growth. The added effects of non-steady-state growth, diverging lamellae, and the effect of nucleation site (grain boundary vs. carbide inclusions) will be highlighted.

3:10 PM  
Developing Internal Friction Capabilities for Defect Characterization in Actinides: Taylor Jacobs1; Clarissa Yablinsky1; Meghan Gibbs1; Franz Freibert1; Tarik Saleh1; 1Los Alamos National Laboratory
    Defect structures, elastic moduli, and phase transformation behaviors of actinides and other relevant metal alloys are being investigated with internal friction using a dynamic mechanical analyzer (DMA). Internal friction is a measurement of time/temperature dependent anelastic deformation that has been used to study defects (solutes, dislocations, phase/grain boundaries) and phase changes (diffusional and shear based) in a wide variety of materials for over 90 years. However, limited internal friction experimentation has been performed on uranium systems and even fewer information is available on plutonium. The current work seeks to utilize modern DMA capabilities for quantitative characterization of defects generated from processing and self-radiation damage in uranium and plutonium alloy systems.

3:30 PM  
High-resolution Temperature-Dependent Elastic Property Measurements of Nuclear Fuels using Resonant Ultrasound Spectroscopy: Jordan Evans1; Ursula Carvajal1; Jonathan Betts1; Joshua White1; Tarik Saleh1; David Frazer1; Boris Maiorov1; 1Los Alamos National Laboratory
    Approximately 20% of the electricity in the United States is generated by nuclear energy, for which UO2 is the commercial nuclear fuel. Despite its excellent neutronic and chemical properties, UO2 has poor thermal conductivity which decreases with increasing temperature. The thermophysical properties of CeO2 are important due to its relevance to numerous fields, as well as its use as a surrogate material for several actinide oxides. U3Si2 is under consideration as an accident-tolerant fuel (ATF) candidate due to its higher uranium density and thermal conductivity in comparison to UO2. The understanding of these materials’ thermoelastic properties, which dominate their thermal conductivities and govern the efficiency and safety of the conversion of heat to electricity, is critical. In this study, the high-resolution, non-destructive resonant ultrasound spectroscopy (RUS) technique is employed to extract the entire elastic tensor and elastic wave attenuation of these materials from cryogenic temperature to 500 K.

3:50 PM  
Moduli Measurements of Various Fuel and Nuclear Materials Measured at Ambient Temperatures: Tarik Saleh1; Stephen Parker1; Aditya Shivprasad1; David Frazer1; Ursula Carvajal-Nunez1; Meghan Gibbs1; John Dunwoody1; Joshua White1; 1Los Alamos National Laboratory
    Resonant Ultrasound Spectroscopy (RUS) is a powerful means of measuring the elastic modulus of materials very accurately. As such it is a useful tool for characterizing novel materials, measuring the changes in properties due to damage (radiation or otherwise), and as an initial measure of quality in small scale fabrication, specifically to this presentation, in pellets of novel fuel types that were fabricated at Los Alamos National Laboratory. This talk will cover RUS measurements on various fuel materials, including uranium, urania, plutonia/urania MOX fuels, uranium nitrides, thorium nitrides, uranium silicides, various composite fuels and other novel fuel types, as well as nuclear materials such as hydride moderators. Experimental equipment, environment, and challenges while measuring moduli on these actinide bearing materials will be highlighted. Corresponding moduli data from nanoindentation will be presented where available.

4:10 PM  
A6W4Al43 : A New Caged-host for U and Pu: Kevin Huang1; William Nelson2; Alexander Chemey3; Thomas Albrecht-Schmitt3; Ryan Baumbach2; 1Lawrence Livermore National Laboratory; 2National High Magnetic Field Laboratory; 3Florida State University
    We report on a new actinide-hosting caged structure in the form A6W4Al43. The actinides form dimers between adjacent W/Al cages. Multiple thermodynamic and magnetic measurements were performed on the U-member while only magnetization data was obtained for the Pu-member. The Pu's behavior is consistent with delocalized 5f-electric behavior while the U-member displays hybridization effects. The high chemical-tunability of the A6W4Al43 family marks this family as a potential nuclear waste-form and as an attractive and new environment to study 5f-electron physics.