2018 | AFC ACCOMPLISHMENTS 88 As part of the research and development process of replacing the current Zr-based fuel cladding for light water reactors with the more accident tolerant FeCrAl fuel cladding, one of the integral experiments needed to predict behavior is the large-break, loss of coolant accident (LOCA) burst test. FeCrAl has oxidation rates more than 100X slower than Zr up to near its melting point of near 1500°C. The burst test requires a ~30 cm long tube of the material with a uniform diameter and wall thickness. Thus, in the early stages of FeCrAl development, such tubing did not exist in sufficient quantity for this type of experiment. As the project matured and larger batches of the new FeCrAl tube were fabricated, it was now possible to conduct these experiments for the C26M alloy that was inserted into Plant Hatch in February 2018. Project Description: A key objective of the program is to develop reliable performance models for operation and during various accident scenarios for new accident tolerant fuel (ATF) concepts, such as the new FeCrAl cladding. Deploying this new oxidation-resistant ATF cladding will decrease the generation of heat and hydrogen compared to Zr-based claddings and increase coping time in the event of an accident, alowing for more time for mitigation and evacuation. However, prior modeling of FeCrAl cladding used incomplete information on the physical properties of FeCrAl. This project is developing integral data and one incomplete area is the burst behavior of C26M, a 2nd generation FeCrAl alloy with improved strength due to the additions of Mo and Si. Tube burst is inevitable during large break LOCA conditions as tubes are internally pressurized for operation in the pressurized water operating. When the coolant (pressurized water) is lost, the tubes now have an internal stress not balanced by the outside environment.As the temperature increases and the material becomes weaker (and is consumed by oxidation due to oxidation in steam), the tube eventually bursts. The burst temperature and the size of the burst determine when and how much fuel might be released to the environment during various accident scenarios. Accomplishments: The goal in 2018 was to burst test C26M FeCrAl tube specimens from multiple batches and determine the performance of this new material relative to (1) first generation FeCrAl Burst Testing of ATF Cladding Materials Principal Investigator: Bruce A. Pint Burst testing in steam of the new C26M FeCrAl alloy has shown superior burst behavior to first generation FeCrAl tubing and smaller burst openings at higher internal pressure.