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A. Pint Compared to the current UO2/ Zr-based alloy fuel system, alter- native cladding materials need to offer slower oxidation kinetics and a smaller enthalpy of oxidation in order to significantly reduce the rate of heat and hydrogen generation in the core during a coolant-limited beyond design basis accident. The steam oxidation behavior of candidate materials is a key metric in the evaluation ofATF concepts and also an important input into models. The SevereAccidentTest Station at Oak Ridge National Laboratory (ORNL) is able to measure steam oxidation behavior at up to 1700°C. Project Description: The project is examining the steam oxidation behavior of candidate materials suggested by the research community (i.e. community testing) and supporting ORNL work on the development of FeCrAl and SiC. The steam oxidation data being collected at 1200°-1700°C is unique as no prior work has considered steam oxidation of alloys at such high temperatures, particularly near the solidus temperature of FeCrAl at ~1500°C. A key objective of the program is to develop reliable performance models. However, prior modeling work of FeCrAl cladding used incomplete information on the physical properties of FeCrAl. Therefore, this project is developing integral data on the melting points of oxides and alloys as well as the structural integrity of FeCrAl compared to Zr-based cladding at up to 1700°C in steam. In addition, the steam oxidation behavior of FeCrAl after 1-yr exposures to LWR conditions was evaluated in ramp (i.e. heating at 5°C/min) testing up to 1500°C. Accomplishments: To support community testing, steam oxidation testing of the MIT Fe-12Cr-3Si was conducted, showing good steam oxidation up to 1000°C but more rapid attack at 1100°C where Fe-rich oxides formed at the specimen edges. Based on the model Fe-Cr alloy work at ORNL, it is possible that a combination of Mo, Mn and Si additions could reduce the required Cr content in a Fe-Cr alloy to lower than 20%. However, recent char- acterization work of a model Fe-Cr alloy showed that a protective SiO2 layer did not form at the Cr2O3-metal interface after exposure in steam at 1200°C like it did at lower temperatures. Therefore, it is questionable if Fe-Cr alloys could form a protective oxide at temperatures above 1200°-1300°C and be a viable alternative to FeCrAl alloys, which form a more stable alpha-Al2O3 scale and remain protective to ~1500°C in steam. High (>12%) Cr content alloys will be susceptible to alpha´ embrittle- ment under LWR-relevant irradiation temperature and dose regimes. Another area that was investigated this year was the behavior of model FeCrAl alloys after exposure to LWR service conditions for 1 year. Ramp testing was performed in 1 bar steam This project is testing candidate accident tolerant cladding materials at up to 1700°C steam to assist in materials development efforts and support the development of performance models