Seaborg Institutes: Emerging Topics in Actinide Materials and Science: Thermodynamic/Radiobiology
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
Thursday 8:30 AM
March 23, 2023
Room: 28A
Location: SDCC
Session Chair: Shuxiang Zhou, INL; Rory Kennedy, INL
8:30 AM Invited
Elucidating the Corrosion Mechanism of Commercial Ni-based Superalloys in UCl3 Containing-chloride Molten Salt Systems: Trishelle Copeland-Johnson1; Xavier Quintana2; Michael Woods1; Ruchi Gakhar1; Daniel Murray1; Guoping Cao1; Lingfeng He1; 1Idaho National Laboratory; 2Oregon State University
The United States Department of Energy is committed to the advancement of nuclear reactor technology through initiatives such as the Advanced Reactor Development Program (ARDP), to diversify the United States energy portfolio towards more sustainable energy options, including demonstration by industry partners of molten salt fast reactors (MSRs). Construction of MSR technology requires qualified nuclear structural materials. Unfortunately, there are no current materials that meet current qualification requirements dictated by the Nuclear Regulatory Commission for construction of MSRs. Adapting current structural material qualifications requires expansion of our current knowledgebase on corrosion performance. In this investigation, we assess microstructural changes in Inconel 617, Hastelloy N, and Hastelloy C-276 after exposure to a UCl3-containing salt system through a multi-modal characterization approach, including computer tomography and electron microscopy. The findings from this investigation will further expand our assessment of the corrosion performance of structural materials being investigated for construction of MSR components.
9:00 AM Invited
Practical Approach to Modeling the Complex Thermochemistry of Actinide-Containing Molten Salts: Theodore Besmann1; Jacob Yingling1; Juliano Schorne-Pinto1; Johnathan1; Mina Aziziha1; Clara Dixon1; Jorge Paz Soldan Palma1; Ronald Booth1; Amir Mehdi Mofrad1; joshua Wermers1; 1University of South Carolina
It is well understood that highly polarizable ions in molten salts lead to short-range ordering/polymerization that makes it difficult to represent salt thermochemistry. This is particularly the case for actinide-containing salt melts where the coordination of species is seen to vary with temperature and composition as observed in experimental structural studies and in ab initio molecular dynamics simulations. Simple solution models fail to capture this tendency as they cannot accommodate the influence of significant non-ideal configurational entropy. This presentation will discuss application of the widely used modified quasi-chemical model in the quadruplet approximation for such systems which has been demonstrated to well represent short-range ordering between second nearest neighbors using pair exchange reactions. Unlike first principles approaches it has a low computational cost and easily accommodates multi-element systems. The modeling of actinide-containing salt melts will be demonstrated in relation to real-time observations of behavior.
9:30 AM
Revisiting the U-Zr Phase Diagram: A Critical Review: Walter Williams1; Jarrod Lund2; Maria Okuniewski2; Edwin Garcia2; 1INL; 2Purdue University
Since the 1950s, the uranium-zirconium (U-Zr) system has been investigated for use as a reference fuel for fast reactors. Thus, the development of an understanding of the thermally and compositionally induced crystallographic phases is critical for further advancement of this technology. A comparison of the two most widely reported phase diagrams, Bauer and Rough (developed in the 1950s) and that of Sheldon and Peterson (developed in the 1980s) show inaccuracies and differences that motivated a critical review on the phase transformations within the U-Zr system. Here, by combining new experimental measurements and emerging machine learning tools, an updated free energy description is presented to reconcile the already published and new thermodynamic data.
9:50 AM Cancelled
Thermodynamics of Plutonium, Its Alloys and Defects: Franz Freibert1; 1Los Alamos National Laboratory
Plutonium in its elemental form is semi-metallic in nature and exhibits many confounding behaviors for a single component system when exposed to temperature and pressure. One informative concept which enables researchers to better understand this system is that of thermodynamics. Discussed will be the application of thermodynamics to Pu and its alloys, in particular, its thermophysical properties of bulk modulus B, thermal expansion alpha, specific heat Cp and density rho. Thermophysical quantities are derivable from first-principles calculations, so modern theoretical tools such as the electronic structure theory implemented via Density Functional Theory are extremely useful in connecting quantum mechanics and thermodynamics. Extending these thermodynamic concepts to radiogenesis and kinetic evolution of defects and the resultant broad range of phenomena are proving crucial to the ultimate understanding of thermodynamic instabilities and aging effects in plutonium. LA-UR-22-26860
10:10 AM Break
10:30 AM Invited
Elucidating the Radiobiology of Alpha Particles in Cancer Therapy: Sandra Davern1; Miguel Toro-Gonzalez1; Amber Bible1; 1Oak Ridge National Laboratory
Targeted alpha therapy utilizes the high-energy deposition and short pathlength of alpha particle emissions to induce DNA double-strand breaks. These are difficult for the cell to repair and, in sufficient amounts, overwhelm DNA repair mechanisms, culminating in cell death. Consequently, their impact on surrounding cells through direct and indirect effects of radiation needs to be evaluated. Clinical trials with Ac-225 (t1/2 = 9.92 days) highlight its potential for eradicating metastatic disease. As targeted alpha therapy becomes accepted and used as a treatment for cancer at earlier stages of disease, it will be important to study the impacts of alpha-emitting radionuclides at a cellular level. Actinium-225 has four alpha emitters in its decay chain, with Bi-213 (t1/2 = 45.6 min) and Fr-221 (t1/2 = 4.9 min) having significant half-lives. Recent assessment of the effect of targeted and untargeted delivery of Ac-225 to breast and ovarian cancer cells will be discussed.
11:00 AM Invited
Advancing Actinium-225 Coordination Chemistry and Chelator Development for Targeted Alpha Therapy: Megan Simms1; Caroline Lara1; Alex Ivanov1; Nikki Thiele1; 1Oak Ridge National Laboratory
Actinium-225 is under intense investigation for use in targeted alpha therapy, a rising cancer treatment strategy that couples the cytotoxicity of alpha particles with the tumor specificity of biological targeting vectors to selectively eradicate cancer cells. To successfully harness Ac-225 for this application, the Ac ion must be stably bound to the targeted construct via a bifunctional chelator to prevent its redistribution to healthy tissues in vivo and subsequent off-target radiotoxicity. In support of the development of more effective chelators for Ac-225, we present our efforts to advance the fundamental coordination chemistry of the Ac(III) ion. Specifically, we describe the experimental determination of thermodynamic stability constants of Ac-225 complexes with a series of chelators relevant to targeted alpha therapy. Furthermore, we discuss how these data can be leveraged to guide future ligand design efforts for this underexplored radioactive ion, and present new chelation platforms developed in our lab to date.
11:30 AM
Structural Changes in Molten Salt Fuel and/or Waste Stream Compounds Cs2UCl6 and Cs2UO2Cl4 from Room Temperature to Melting: Benjamin Walusiak1; Alice Smith2; Sven Vogel2; Stepehn Parker2; Shane Mann2; Alberto Gomez2; Adam Phelan2; Christopher Cahill1; 1George Washington University; 2Los Alamos National Laboratory
Recently the advantages of molten uranium chloride fuels have been recognized for fast spectrum molten salt reactors (FSMSR’s) in particular. Attention should therefore be given to uranium chloride phases, including those that could form as fission in the reactor progresses, or in MSR waste streams. Cesium, being a major fission product, is known to form salts with uranium and uranyl chlorides in the form of Cs2UCl6, and Cs2UO2Cl4 (U4+ and U6+ respectively). Although these compounds are known, their behavior from room temperature to melting, including phase transitions and lattice expansion, has not been completely and unambiguously carried out. As such, a rigorous structural characterization of these phases, from room temperature to melting, has been performed. Phase transitions, including melting, and crystal lattice changes have been characterized by powder X-ray diffraction (PXRD, George Washington University), differential scanning calorimetry (DSC), and time of flight neutron diffraction (Los Alamos National Laboratory).