b'Understanding SaltUnderstanding fundamental salt chemistry enables corrosion Chemistry and Corrosionresistant materials development for molten salt reactors.Control of Chloride SaltsC hloride salts are candidate fuel and coolant for some molten salt reactor concepts as they offer potential for sustained operation in a fast neutron for Molten Salt Reactors spectrum with minimal salt processing, passive safety, and a high power density. However, molten chlorides present significant corrosion challenges to structural materials. Currently, the corrosion data for relevant metal alloys in chloride salts are very limited, presenting technical risks for reactor design and operation. This project provided critical baseline data to understand the salt chemistry and corrosion control of two chloride saltssodium chloride (NaCl)-uranium chloride PROJECT NUMBER:(UCl) and NaCl-magnesium chloride (MgCl)most relevant to chloride molten 20A44-126 salt reactors. From systematic experimentation and multiphysics based density TOTAL APPROVED AMOUNT:functional theory modeling, the following major important findings were made on $1,532,900 over 3 years the corrosion of candidate materials for molten salt reactors in chloride salts, salt redox potential control, and guidelines for developing corrosion resistant alloys for PRINCIPAL INVESTIGATOR:chloride molten salt reactors for long-term operation. Guoping CaoThe correct testing methodology for evaluating corrosion of materials is very CO-INVESTIGATORS: important. Galvanic corrosion and dissimilar materials effects during corrosion Jianguo Yu, INL testing can significantly accelerate the corrosion of alloys in chloride salts. Junhua Jiang, INL Sparging a gas mixture of argon and hydrogen into molten chloride salt could Ruchi Gakhar, INL dramatically decrease the corrosion of materials in chloride salts. Yaqi Wang, INL The effect of fission product cesium iodide on 316H stainless steel in NaCl-MgCl Haiyan Zhao, University of Idaho was insignificant. After systematic testing of many different iron-based and nickel-based alloys in NaCl-MgCl salt under identical testing conditions, it was found that Hastelloy C-276 exhibited outstanding corrosion resistance with a weight loss lower than that of pure nickel. Hastelloy C-22 also exhibited good corrosion resistance. Analysis of the systematic corrosion tests on many different alloys could provide fundamental guidelines for developing alloys for chloride molten salt reactors that would exhibit good corrosion resistance and mechanical properties for long-term operations. First principles density functional theory multiphysics modeling found tremendous disproportionate behavior and chemical stability difference of UCl and uranium fluoride (UF). The modeling shows that UCl is much more stable than UF, suggesting different requirements for chloride- and fluoride-fueled molten salt reactors. 56'