Abstract:Understanding the corrosion of uranium is important for its safe, long-term storage. Uranium metal corrodes rapidly in air, but the exact mechanism remains subject to debate. Atom Probe Tomography was used to investigate the surface microstructure of metallic depleted uranium specimens following polishing and exposure to moist air. A complex, corrugated metal-oxide interface was observed, with approximately 60 at.% oxygen content within the oxide. Interestingly, a very thin (~5 nm) interfacial layer of uranium… Show more
“…The concentration of Si was less than 3 at%, and those of O, Ni, and Al were all less than 2 at% in samples analysed, whereas H concentration was more significant, and was found in concentrations of 4–20 at%. The H concentration can be attributed to the formation of UH when U is in the presence of H 17 . Sources of H leading to the formation of UH could be water used in the bulk metallographic polishing procedure, focused ion beam (FIB) preparation of APT needle specimens, and/or residual H from the APT analysis chamber.Figure 4Compositional and isotopic profiles of DUMo and LEUMo.…”
Spatially resolved analysis of uranium (U) isotopes in small volumes of actinide-bearing materials is critical for a variety of technical disciplines, including earth and planetary sciences, environmental monitoring, bioremediation, and the nuclear fuel cycle. However, achieving subnanometer-scale spatial resolution for such isotopic analysis is currently a challenge. By using atom probe tomography—a three-dimensional nanoscale characterisation technique—we demonstrate unprecedented nanoscale mapping of U isotopic enrichment with high sensitivity across various microstructural interfaces within small volumes (~100 nm
3
) of depleted and low-enriched U alloyed with 10 wt% molybdenum that has different nominal enrichments of 0.20 and 19.75%
235
U, respectively. We map enrichment in various morphologies of a U carbide phase, the adjacent γ-UMo matrix, and across interfaces (e.g., carbide/matrix, grain boundary). Results indicate the U carbides were formed during casting, rather than retained from either highly enriched or depleted U feedstock materials. The approach presented here can be applied to study nanoscale variations of isotopic abundances in the broad class of actinide-bearing materials, providing unique insights into their origins and thermomechanical processing routes.
“…The concentration of Si was less than 3 at%, and those of O, Ni, and Al were all less than 2 at% in samples analysed, whereas H concentration was more significant, and was found in concentrations of 4–20 at%. The H concentration can be attributed to the formation of UH when U is in the presence of H 17 . Sources of H leading to the formation of UH could be water used in the bulk metallographic polishing procedure, focused ion beam (FIB) preparation of APT needle specimens, and/or residual H from the APT analysis chamber.Figure 4Compositional and isotopic profiles of DUMo and LEUMo.…”
Spatially resolved analysis of uranium (U) isotopes in small volumes of actinide-bearing materials is critical for a variety of technical disciplines, including earth and planetary sciences, environmental monitoring, bioremediation, and the nuclear fuel cycle. However, achieving subnanometer-scale spatial resolution for such isotopic analysis is currently a challenge. By using atom probe tomography—a three-dimensional nanoscale characterisation technique—we demonstrate unprecedented nanoscale mapping of U isotopic enrichment with high sensitivity across various microstructural interfaces within small volumes (~100 nm
3
) of depleted and low-enriched U alloyed with 10 wt% molybdenum that has different nominal enrichments of 0.20 and 19.75%
235
U, respectively. We map enrichment in various morphologies of a U carbide phase, the adjacent γ-UMo matrix, and across interfaces (e.g., carbide/matrix, grain boundary). Results indicate the U carbides were formed during casting, rather than retained from either highly enriched or depleted U feedstock materials. The approach presented here can be applied to study nanoscale variations of isotopic abundances in the broad class of actinide-bearing materials, providing unique insights into their origins and thermomechanical processing routes.
“…Concentration of Si is less than 3 at%, O, Ni, and Al are all less than 2 at% in samples analyzed, whereas H concentration is more significant, and was found in concentrations of 4-20 at%. The H concentration can be attributed to the formation of UH when U is in the presence of H [17]. Sources of H leading to the formation of UH could be water used in the bulk metallographic polishing procedure, FIB prepareation of APT needle specimens and/or from residual H background from the APT analysis chamber.…”
Section: D Elemental Distribution Across Precipitate-matrix Interfacesmentioning
confidence: 99%
“…The LEU-10Mo was subjected to subsequent thermo-mechanical processing treatments (hot and cold rolling) to form the final fuel foil. Additional sample fabrication details are reported in References [47, 19,17]…”
Section: Materials Fabricationmentioning
confidence: 99%
“…Uranium (U) is the heaviest element naturally occurring in the Earth's crust in significant amounts, and is used both in its natural, processed, and anthropogenic forms. U isotopes are central to a diverse set of scientific disciplines, most notably earth and planetary sciences [1][2][3][4][5][6][7][8], toxicology, environmental monitoring and bioremediation [9][10][11], and the nuclear fuel cycle, forensics, and safeguards [12][13][14][15][16][17][18][19][20][21][22]. Specifically in nuclear fuel cycle applications, the amount of the fissionable U isotope ( 235 U) relative to all U (defined as enrichment) is a critical parameter in fuel performance, and thus impacts economic viability of nuclear power.…”
Spatially resolved analysis of uranium isotopes in small volumes of actinide-bearing materials is critical for a variety of technical disciplines, including earth and planetary sciences, environmental monitoring, bioremediation, and the nuclear fuel cycle. However, achieving sub-nanometer scale spatial resolution for such isotopic analysis is currently a challenge. By using atom probe tomography, a three dimensional nanoscale characterization technique, we demonstrate unprecidented nanoscale mapping of uranium isotopic enrichment with high sensitivity across various microstructural interfaces within small volumes (100 nm 3 ) of depleted and low enriched uranium alloyed with 10 wt % molybdenum with different nominal enrichments of 0.20 and 19.75% 235 U respectively. The approach presented here can be applied to study nanoscale variations of isotopic abundances in the broad class of actinide-bearing materials, providing unique insights into their origin and thermo-mechanical processing routes.
“…Alloys applied in nuclear reactors 1,2 , gas turbines 3,4 , heterogeneous catalysis 5,6 , automotive internal combustion engines 7 , and electronic devices 8,9 are routinely exposed to high-temperature, corrosive, and oxidising environments. Oxidation of alloys in service can degrade material properties and performance, raising significant safety and economic concerns.…”
A multimodal chemical imaging approach has been developed and applied to detail the dynamic, atomic-scale changes associated with oxidation of a zirconium alloy (Zircaloy-4). Scanning transmission electron microscopy, a gas-phase reactor chamber attached to an atom probe tomography instrument, and synchrotron-based X-ray absorption near-edge spectroscopy were employed to reveal morphology, composition, crystal, and electronic structure changes that occur during initial stages of oxidation at 300 °C. Oxidation was carried out in 10 mbar O2 gas for short exposure times of 1 and 5 min. A multilayered oxide film with a cubic ZrO adjacent to the oxide/metal interface, a nanoscopic transition region with a graded composition of ZrO2−x (where 0 < x < 1), and tetragonal ZrO2 in the outermost oxide were formed. Partitioning of the major alloying element (tin) to the oxide/metal interface and heterogeneously within the oxide accompanied the development of the layered oxide. Our work provides a rapid, high-throughput approach for detailed characterisation of initial stages of zirconium alloy oxidation at an accelerated time scale, with implications for several other alloy systems.
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