Carbon Effects on Corrosion in Molten Fluoride Salt
Chan, Kevin Jeremy
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The fluoride salt-cooled high temperature reactor (FHR) is a Generation IV reactor concept that uses molten fluoride salt as the primary coolant to enable breakthrough improvements in economics and safety over the current generation of reactors. However, graphite fuel elements and other carbon components present large surface area to the coolant salt. They can degrade structural alloys by driving carburization or by forming metal carbides with corrosion products. A thorough understanding of the interactions between environmental carbon and structural alloys is necessary for the successful development and deployment of FHRs. Key knowledge gaps of carbon-alloy interactions in molten fluorides were addressed in this work. Simultaneous chromium depletion and carburization behavior of several alloys were studied in multi-duration exposure tests. Pre-carburization experiments evaluated the beneficial and detrimental effects of carburization related to corrosion. Most importantly, the mechanism of carbon transport was investigated in support of future designs of carburization control measures.