Materials in Nuclear Energy Systems (MiNES) 2021: Nuclear Fuel Cycles- Session I
Program Organizers: Todd Allen, University of Michigan; Clarissa Yablinsky, Los Alamos National Laboratory; Anne Campbell, Oak Ridge National Laboratory
Tuesday 8:00 AM
November 9, 2021
Room: Conference Center A
Location: Omni William Penn Hotel
Session Chair: Clarissa Yablinsky, Los Alamos National Laboratory
8:00 AM Invited
Recent Advances in Pyroprocessing of Light Water Reactor Fuel: Krista Hawthorne1; 1Argonne National Laboratory
Reprocessing of used nuclear fuel is a key step in enabling the deployment of advanced nuclear reactors and minimizing the amount of radioactive material that must be disposed of as waste. Pyroprocessing safely and efficiently recycles used nuclear fuel into usable components by applying electrochemical operations in molten salt electrolytes. For light water reactor (LWR) fuel, the oxide is electrochemically reduced to metal, then electrorefined to recover a pure uranium product. The fission products are removed from the salt electrolyte and immobilized in durable waste forms for disposal. These processes are well understood at the laboratory scale, but the impacts of salt chemistry and cell geometry on process efficiencies must be determined on scaled-up systems to optimize production methods, process controls and monitoring, and product quality. Recent work at Argonne National Laboratory on understanding aspects of the process electrochemistry and engineering at multiple scales will be discussed.
8:40 AM
Instrumentation in Molten Salt Systems: Commercial Availability, Custom Solutions, and Gaps: Adam Burak1; Xiaodong Sun1; Ethan Hamilton2; Michael Simpson2; Dimitris Killinger3; Supathorn Phongikaroon3; 1University of Michigan; 2University of Utah; 3Virginia Commonwealth University
Few commercial instruments can be applied to molten salt work. Others require fabrication/construction in-house and some do not exist or are in their infancy. Monitoring molten salt parameters such as temperature, composition, and redox potential is essential to infer the property evolution of materials exposed to molten salts. Commercialized technology is sparse for measuring parameters in molten salts. To measure parameters, more difficult than temperature, there is a dearth of technologies commonly requiring instruments to be built in-house. Reliable, optimized instruments, with quantified uncertainty, facilitate advanced and comparable studies. The use of uniform instrumentation reduces time spent designing and characterizing instrumentation, which can be better spent designing experiments, and ease comparison between different studies in the literature. This work discusses commercially available instruments for molten salts, prevalent in-house solutions, and where development of new instrumentation is needed. In addition, recent advances in instrumentation development for the VTR will be discussed.
9:00 AM
Deliquescence of Eutectic LiCl-KCl Diluted with NaCl for Interim Waste Salt Storage: Claire Decker1; Jerry Howard1; Levi Gardner2; Allison Harward1; Guy Fredrickson3; Tae-Sic Yoo3; Michael Simpson1; Krista Carlson1; 1University of Utah; 2Argonne National Laboratory; 3Idaho National Laboratory
Molten eutectic LiCl-KCl is a widely used electrolyte for electrorefining uranium from spent nuclear fuel. Due to the hygroscopic nature of this salt, careful handling and storage is required to avoid deliquescence and corrosion of container materials. This study investigated a potential processing path for reducing the deliquescence through dilution with NaCl. The hydration behavior of LiCl-KCl diluted with NaCl was evaluated in terms of mass gain due to water absorption, visual evidence of deliquescence, and visual evidence of corrosion to stainless-steel containers in a humid air environment. Pure LiCl-KCl exhibited a 50 mass% increase due to water absorption and exhibited deliquescence after 24 hours. 89 mass% NaCl was required in order to prevent deliquescence. Dilution with 89% NaCl was also found to protect stainless steel crucibles from corrosion. Corrosion, thus, appears to require deliquescence. While NaCl dilution decreases steady state hydration and eliminates deliquescence, storage volume is increased ~10x.
9:20 AM
Perovskite-derived Cs2SnCl6-Silica Composites as Advanced Waste Forms for Chloride Salt Wastes: Yang Kun1; Brian Riley2; John Vienna2; Dong Zhao1; Jie Lian1; 1Rensselaer Polytechnic Institute; 2Pacific Northwest National Laboratory
Advanced materials and processes are required to separate halides and fission products from complex salt waste streams associated with the chemical reprocessing of used nuclear fuels and molten salt reactor technologies and immobilize them into chemically durable waste forms. We explore an innovative concept using metal-halide perovskites (MHPs) as advanced host phases to incorporate Cs and Cl with very high waste loadings. Wet chemistry-synthesized Cs2SnCl6 powders from CsCl salts are encapsulated into a silica matrix to form a composite using spark plasma sintering with tunable Cs and Cl loadings. The MHP-silica composites display exceptional chemical durability with the long-term release rates of Cs and Cl comparable to or outperforming the state-of-the-art waste form materials despite significantly higher waste loadings. The scalable synthesis of the MHPs from wet-chemistry opens up new opportunities in designing advanced salt waste forms for the sustainable development of advanced fuel cycles and next-generation reactor technologies.
9:40 AM
A First-principles Database Approach to Predicting Trans-uranic Waste Forms: Matthew Christian1; Hunter Tisdale1; Greg Morrison1; Adrian Hines1; Hans-Conrad zur Loye1; Theodore Besmann1; Amir Mofrad1; 1University of South Carolina
First-principles density-functional theory (DFT) provides an efficient way to screen trans-uranic (TRU) waste form candidates. To this end, the Center for Hierarchical Waste form Materials (CHWM) has created a structural database based on known parent structures to generate hypothetical TRU crystal structures. The calculated formation enthalpies for the candidate structures are then compared to formation enthalpies of competing reaction products, following the methodology of the Open Quantum Materials Database (OQMD). The results provide relative stabilities that are used to speculate on formation probability. Our calculations using this approach have led to the discovery of new structures, encouraging its expanded adoption.
10:00 AM Break