Chemistry and physics of graphite in fluoride salt reactors
Abstract: Graphite is a ubiquitous material in nuclear engineering. Among Generation IV reactor designs, graphite serves as a reflector or fuel element material in Fluoride-Salt-Cooled-High-Temperature Reactors (FHRs), Molten Salt Reactors (MSRs), and High-Temperature-Gas-Reactor (HTGRs). Graphite versatility in nuclear systems stems from its unique combination of mechanical, thermal, chemical, and neutronic properties. These properties vary across graphite grades and are influenced by operational parameters like temperature, radiation, and chemical environment. While the role of these parameters is well understood for HTGRs, the effect of graphite exposure to fluoride salts in FHRs and MSRs has not been fully characterized yet. In these reactors, graphite can be subject to multiple mechanisms of interaction with the salt, including salt-infiltration in graphite pores, chemical reactions with the salt constituents, and tribo-chemical wear. These mechanisms can have an impact on graphite’s integrity and functional performance in the reactor, including its ability to immobilize tritium, its irradiation-resistance, and its sensitivity to degradation under air ingress. This seminar will describe physical and chemical mechanisms of interactions of fluoride salts with graphite and discuss their impact on reactor engineering.
Bio: Lorenzo Vergari is a Ph.D. candidate in the Department of Nuclear Engineering at the University of California, Berkeley. He is a member of the SALT research group, and he is advised by Dr. Raluca Scarlat. Lorenzo’s experimental and computational interests lie in the chemistry and engineering of coolants and blankets and their interactions with reactor materials. Before joining UC Berkeley, he received a M.S. in Nuclear Engineering from Polytechnic University of Milan, a M.S. in Energy and Nuclear Engineering from Polytechnic University of Turin, and a B.S. in Energy Engineering from Polytechnic University of Milan.