Seaborg Institutes: Emerging Topics in Actinide Materials and Science: Actinide Synthesis and Physics
Sponsored by: TMS Structural Materials Division, TMS: Nuclear Materials Committee
Program Organizers: J. Rory Kennedy, Idaho National Laboratory; Taylor Jacobs, Helion Energy; Krzysztof Gofryk, Idaho National Laboratory; Assel Aitkaliyeva, University of Florida; Don Wood, Idaho National Laboratory
Tuesday 2:30 PM
March 21, 2023
Room: 28A
Location: SDCC
Session Chair: Eteri Svanidze, MPI CPfS; Krzysztof Gofryk, Idaho National Laboratory
2:30 PM Invited
The Quest for Californium(II) and the Importance of Trail Markers from Other Transuranium Elements and Lanthanides: Thomas Albrecht-Schoenzart1; 1Colorado School of Mines
The standard reduction potential of californium(III) to californium(II) has been measured to be anomalously low compared to both earlier actinides and to lanthanides with either similar ionic radii or the same number of f electrons. This potential is similar to that of Sm(III) to Sm(II) and thus samarium provides a potential electrochemical analog for fine-tuning the challenging reduction chemistry. However, Sm(II) should be considerably larger than Cf(II) and the coordination chemistry might be different enough that smaller Ln(II) cations are needed to guide ligand design. Moreover, directions provided by Ln(II) cations can still lead one down the wrong path because they do not account for radiolytic reactions or the contracted bond distances observed with actinides. By combining both Ln(II) and earlier actinide chemistry, we have finally isolated a Cf(II) molecule and now understand why it has been so elusive. This talk with detail that journey to discovery.
3:00 PM Invited
End to End Plutonium Processing at LLNL: Kiel Holliday1; 1Lawrence Livermore National Laboratory
A new aqueous recovery lab for plutonium installed at LLNL features mirror glovebox lines, which result in a high degree of flexibility while still meeting LLNL missions. Different variables, isotopics, or process conditions can be explored in one line, while maintaining ideal conditions in another. The capabilities stood up are a nitric acid-based purification process. Dissolution, anion exchange, and oxalate precipitation are employed to recover pure plutonium oxide product. The resulting purified plutonium oxide is then sent to pyrochemical processing. At LLNL the complete pyrochemical flowsheet has been demonstrated at small scale (100 – 200 g) allowing for the creation of custom alloys and isotopic compositions. Recently, partial direct oxide reduction, molten salt extraction, electrorefining, and alloying were used to produce an Accelerated Aged Alloy of plutonium. Here we present the features of the aqueous recovery laboratory in greater detail and the equipment modifications that enable small scale pyrochemical processing.
3:30 PM
From Mild Hydrothermal to High Temperature Solutions: Crystal Growth of New Uranium and Transuranium Phases: Hans-Conrad Zur Loye1; Kristen Pace1; Travis Deason1; Gregory Morrison1; Theodore Besmann1; Jake Amoroso2; David DiPrete2; 1University of South Carolina; 2Savannah River National Laboratory
The crystal growth of uranium and transuranium containing phases has been accomplished via two different crystal growth routes, mild hydrothermal and high temperature solution flux growth. In both cases we are targeting the preparation of new compositions to evaluate their potential use as nuclear waste forms. The mild hydrothermal route works extremely well for crystallizing complex fluoride phases, such as Na3GaU6F30, Na3AlNp6F30, Na3FePu6F30, and Cs2NiNp3F16, while the high temperature flux route works well for crystallizing oxide phases, such as Cs2PuSi6O15 and Na2PuO2(BO3). The synthesis and structures of these phases will be discussed, along with our appraoch of identifying potential compositions that we can pursue synthetically.
3:50 PM
The Path Toward Molecular Beam Epitaxy of Single Crystalline Actinide Materials: Kevin Vallejo1; Brelon May1; Cody Dennett1; Paul Simmonds2; David Hurley1; Krzysztof Gofryk1; 1Idaho National Laboratory; 2Boise State University
Actinide-based materials possess unique physics due to the presence of 5f electrons. However, samples with high purity and crystallinity are required for the effective examination of unique quantum phenomena and to provide accurate experimental values for theoretical models. Molecular beam epitaxy is a non-equilibrium synthesis technique which presents an attractive avenue for the fabrication and study of monocrystalline actinide materials as it offers a high degree of control over purity, dimensionality, strain, and interfaces between monolithically grown materials. The methods for controlling and accessing the complex oxidation states of actinide elements (such as U and Th) are not fully understood. It is important to comprehend the formation mechanisms of materials with maintenance, safety, and a radioactive issues prior to introducing them to the deposition chamber. Therefore, transition metals with similarly intricate bonding arrangement possibilities will be initially investigated to gain insight on how to engineer actinide materials.
4:10 PM Break
4:30 PM Invited
Enhanced Spin Orbit Coupling in the Actinides: Peter Riseborough1; 1Temple University
A number of actinide intermetallic compounds, such as the uranium monochalcogenides, show giant magnetic anisotropies. We show that giant anisotropies result from the Coulomb enhancement of the spin-orbit coupling, and that the enhancement is largest for highly hybridized systems that are in the close proximity to a quantum critical point. The enhancement is attributed to the constructive interference of atomic Coulomb and spin-orbit scattering processes of electrons in hybridized bands. The calculational method consists of a variational method in where off-diagonal atomic correlations induced by the spin-orbit coupling are enhanced by the off-diagonal elements of the Coulomb interaction with the same symmetry. The method is applied to the calculation of the magnetic anisotropy.
5:00 PM Invited
Magnetic and Electronic Properties of Actinides Affected by Polar Bonding: Ladislav Havela1; 1Charles University
Metallic state of light actinides and their compounds leads typically to delocalization of 5f electronic states. If the 5f band becomes broad due to a short inter-actinide spacings, e-e correlations are suppressed, yielding weak Pauli paramagnetism. In the system of Uranium, the Hill limit of approx. 340 pm should be exceeded to provide conditions for magnetic order. More recently it has been realized that a polar character of bonding provides a further tuning possibility. Typically, at U systems, a charge transfer towards ligands, affecting mainly the 6d states, reduces the 5f-6d hybridization, and supports thus formation of magnetic moments and their ordering. Such tendency has been studied at U hydrides and at Zintl phases (UCu2P2), the latter yielding TC values approaching room temperatures under pressure.