Thermodynamics of Materials in Extreme Environments: On-Demand: Thermodynamics of Nuclear Materials and Minerals
Sponsored by: ACerS Basic Science Division, ACerS Energy Materials and Systems Division
Program Organizers: Xiaofeng Guo, Washington State University; Kristina Lilova, Arizona State University; Kyle Brinkman, Clemson University; Alexandra Navrotsky, Arizona State University; Jake Amoroso, Savannah River National Laboratory; Xingbo Liu, West Virginia University; Gustavo Costa, NASA Glenn Research Center
Friday 8:00 AM
October 22, 2021
Room: On-Demand Room 9
Location: MS&T On Demand
Session Chair: Xiaofeng Guo, Washington State University; Gustavo Costa, NASA Glenn Research Center
Invited
Thermodynamics of An-Cl Complexes at High Temperature and Pressure: Ping Yang1; Xiaobin Zhang1; Morgan Kelley1; Jason Baker1; Hakim Boukhalfa1; Artaches Migdissov1; Hongwu Xu1; 1Los Alamos National Laboratory
Nuclear energy represents a critical means to ensure sustainable energy supplies and curb greenhouse gas emissions. However, the development of nuclear energy systems is still hampered by safety concerns associated with the handling, processing, and disposing of spent fuel and high-level waste. One leading candidate approach is the storage of spent fuel in geological repositories. The behavior of actinides in high P-T environments is a fundamental knowledge gap with little understanding of complexation and thermodynamics of 5f-elements at geothermal relevant P-T conditions of these proposed disposing facilities. In this talk, we will present the impact on the chemical species and their thermodynamics from the elevated temperature and pressure based on the first-principle methods. The predicted results were validated by experimental Raman and XAS measurements in a hydrothermal diamond-anvil cell. The close integration between theory and experiment is the key to push forward the understanding of f-element chemistry at hydrothermal conditions.
Invited
Dissolution of Uranium Based Dioxide in Nitric Acid: Impact of Fission Products and Microstructure: Nicolas Dacheux1; Thomas Barral2; Thibault Kaczmarek2; Malvina Massonnet2; Laurent Claparede1; Nicolas Clavier3; Stephanie Szenknect2; Renaud Podor3; 1University of Montpellier; 2CEA; 3CNRS
SNF dissolution appears as a key step for its reprocessing although complex chemical, structural and microstructural properties complicate the global understanding of its chemical durability. In this field, sintered samples of UO2 doped with FP (mainly lanthanides such as Ce, Nd and Gd or PGM’s) were prepared by wet chemistry routes, sintered then submitted to dissolution tests in various nitric acid solutions to mimic reprocessing conditions. Using a macroscopic approach, the impact of each FP was analysed through the elemental releases in solution. Either lanthanide and PGM elements induced significant modification of the dissolution rates of the ceramics. This macroscopic description was connected to operando monitoring of the evolving solid/solution interface during the dissolution. Preferential dissolution zones (pores, grain boundaries, …) as well as different evolution depending on the crystal orientation in the grains were observed by ESEM, suggesting various progresses of the dissolution reaction at the solid/solution interface.
Cancelled
Thermodynamic Properties of Fluoride Molten Salts from Modeling and Simulations: Shun-Li Shang1; Jorge Paz Soldan Palma1; Brandon Bocklund1; Nathan Smith1; Yi Wang1; Hojong Kim1; Zi-Kui Liu1; 1Penn State University
Rational design and development of molten salts depend on understanding and prediction of critical thermochemical and physical properties of salts such as melting points and solubility of fission products; thus appealing for accurate modeling and especially modeling tools. Using a model system of NiF2-FLiNaK, the present work aims to demonstrate the recent development of our open-source tools PyCalphad (https://pycalphad.org) and ESPEI (https://espei.org) to perform CALPHAD modeling of molten salts by means of the regular model, the ionic liquid model, the associate model, and in particular the modified quasichemical model (MQM), recently implemented in the PyCalphad/ESPEI framework, on an equal footing. The modelled results are compared with experimental results in the literature, the present measurements using electromotive force and differential scanning calorimetry, and the present ab initio molecular dynamics (AIMD) simulations; demonstrating a new pathway for efficient CALPHAD modeling of molten salts using the open-source tools with uncertainty quantification.
Invited
Effective Assessment and Thermodynamic Database Development for Potential Nuclear Reactor Molten Salt Systems: Theodore Besmann1; Juliano Schorne Pinto1; Jacob Yingling1; Johnathan Ard1; Mina Aziziha1; Matthew Christian1; Amir Mofrad1; Mahmut Aslani1; Jake McMurray2; 1University of South Carolina; 2Oak Ridge National Laboratory
The continuing effort to expand the successful Molten Salt Thermal Properties Database – Thermochemical, has driven efforts to improve the accuracy of database values and the efficiency of required assessments. Fundamental studies of salts have made it clear that they experience short-range ordering, and the effect on the resulting coordination numbers on salt thermodynamic properties is captured in the current modified quasi-chemical model in the quadruplet approximation. The accuracy of these models is being improved through the use of multiple system endmembers, better capturing phenomenological behavior with varying temperature and composition. Optimization of systems using experimental and computational information to fit model parameters in such complex systems is problematic, and thus methodologies to more efficiently effect the fits have been developed. These approaches will be described as well as the current state of the database.
Energetics of La, Nd-containing Hydroxylbastnaesite (La1-xNdxCO3OH) Solid Solutions: Vitaliy Goncharov1; Haylea Nisbet2; Andrew Strzelecki1; Chris Benmore3; Hongwu Xu2; Artaches Migdisov2; Xiaofeng Guo1; 1Washington State University; 2Los Alamos National Laboratory; 3Argonne National Laboratory
Hydroxylbastnaesite (LnCO3OH) is a common REE ore mineral that primarily hosts light rare-earth elements (LREE), often occurring as solid solutions in nature. To better understand the nature and the formation mechanism of such deposits, we studied hexagonal La–Nd hydroxylbastnaesite (La1–xNdxCO3OH) solid solutions (x = 0, 0.25, 0.50, 0.75, 1) by synchrotron powder X-ray diffraction, TGA-DSC-MS, and high temperature oxide melt drop solution calorimetry. Two-step decomposition pathways were confirmed for La1–xNdxCO3OH solid solutions. The enthalpies of formation of La1–x</SUB >NdxCO3OH were determined, from which the enthalpies of mixing were derived with an interaction parameter of 12.58 ± 0.16 kJ/mol, suggesting a regular solution model for the mixing of La and Nd. Lastly, we estimated the Gibbs free energy of mixing at various relevant formation temperatures, from which we demonstrated that the favorable formation of La1–xNdxCO3OH solid solution is driven by entropic effects induced by hydrothermal conditions.
Influence of Local Charge and Magnetic Ordering on Point Defect Properties in Magnetite (Fe3O4): Shivani Srivastava1; Blas Uberuaga2; Mark Asta3; 1University of California Berkeley; 2Los Alamos National Laboratory; 3University of California Berkeley; Lawrence Berkeley National Laboratory
The thermodynamic and kinetic properties of iron oxides play important roles in corrosion processes in many structural materials. As part of an effort aimed at understanding such processes under conditions involving irradiation induced defect production in nuclear energy applications, this work is focused on understanding the equilibrium and non-equilibrium properties of point defects in magnetite (Fe3O4). Specifically, we employ first-principles calculations to investigate formation and migration energies of point defects in this material. The low-temperature structure of magnetite features coupled charge, spin and orbital order. This phase undergoes an order-disorder phase transition at around 120K, but there is evidence of strong local order above this transition. A specific focus of the calculations is understanding the effect of this local order on the properties of vacancy and interstitial point defects. The implications of these results on the impact of irradiation on magnetite formation during oxidation/corrosion of iron will be discussed.
Energetics of K-,Ga- Titanate Hollandites: Nancy Birkner1; Mingyang Zhao1; Kyle Brinkman1; 1Clemson University
Hollandites show promise for immobilization of alkali metal radionuclides (e.g. 137Cs fission product of nuclear reactors). The Center for Hierarchical Waste Form Materials previously measured the thermodynamic stability of A-site (Ba,Cs)-containing titanate hollandites of the general form BaxCsyZnx+y/2Ti8-x-y/2O16 and BaxCsyB2x+yTi8-2x-yO16 (x + y = 1.33 and B = Al, Fe, Ga). Enthalpies of formation in order of increasing stability are Ga<Zn<Fe≈Al (notation based on B-sites). Additionally, greater [Cs] increases stability resulting in fractional Cs retention increase under aqueous leaching conditions. Recently, K,Ga - titanate hollandites, (KxGayTi8-x-yO16, x = y) were measured using high temperature oxide melt solution calorimetry. Like previous titanate hollandites, their formation enthalpies are strongly exothermic indicating thermodynamic stability relative to their binary oxides and elements at 25 °C.