UF3 Instability in Molten Fluoride Salts: Mechanisms, Possible Interactions and Redox Control

About the Event

Molten fluoride salt reactors offer a promising pathway to advanced nuclear energy, but their operation requires precise control of the fuel salt redox state to limit corrosion of structural materials. In LiF-based binary and ternary salts, UF3 acts as a reducing buffer. However, this behavior has not been established in NaF-bearing fuel salts. Our research shows that the UF3 buffer systematically breaks down in NaF-bearing fuel salt. This study identifies four instability pathways: (1) disproportionation of UF3 to metallic uranium; (2) reaction with structural metal surfaces; (3) depletion in the presence of a fission product and/or a surrogate compound for PuF3; and (4) formation of insoluble carbides in carbonaceous moderator materials. These pathways occur within the accepted operating window and intensify with thermal history and trifluoride accumulation. These findings represent a fundamental revision of the redox-control framework used for molten salt reactor fuels.

About the Speaker

Nagihan Karakaya is a postdoctoral researcher in Nuclear Engineering at Virginia Tech under the supervision of Dr. Jinsuo Zhang. Her research focuses on redox-control mechanisms in molten salt reactor fuels, including corrosion and material stability in high-temperature ionic liquids; the chemical stability of molten salts; electrochemical sensor development for high-temperature liquids; thermophysical property measurement of metallic and ionic liquids; and the recycling of used fuel into advanced reactor fuel. She earned her M.S. and Ph.D. in Nuclear Engineering from Virginia Tech and her B.S. in Chemical and Process Engineering in Turkey. Her research offers new insight into molten-salt redox chemistry and fuel stability, with implications for reactor design and safety. Her work received first place in the poster presentation at the 2025 Molten Salt Reactor Workshop at Oak Ridge National Laboratory.