Oxidation and embrittlement behavior of FeCrAl-ODS cladding tube under loss-of-coolant accident conditions

Abstract

To evaluate the oxidation and embrittlement behavior of an oxide-dispersion-strengthened FeCrAl (FeCrAl-ODS) cladding tube under loss-of-coolant accident (LOCA) conditions, we conducted isothermal oxidation and ring-compression tests on unirradiated, stress-relieved FeCrAl-ODS cladding tube specimens. Further, we discussed the loss of coolable geometry of the reactor core loaded with the FeCrAl-ODS cladding tubes under LOCA conditions, using data from the ring-compression tests in this study and the integral thermal shock tests from our previous study. The results reveal that oxidation kinetics of the FeCrAl-ODS cladding tube at ▪ is four orders of magnitude lower than that of a conventional Zircaloy cladding tube, which highlights the exceptional oxidation resistance of the FeCrAl-ODS cladding tube. The breakaway oxidation of the FeCrAl-ODS cladding tube was observed at ▪ for durations equal to or exceeding ▪, and melting was observed at ▪. The ring-compression and the integral thermal shock tests indicate that, depending on the oxidation time, the ductile to brittle transition threshold — as determined by the ring-compression test — exists between ▪ and ▪. Meanwhile, the fracture threshold — established through the integral thermal shock test — falls between ▪ and ▪. Therefore, taking a conservative approach based on available data, the fracture and non-fracture results from the integral thermal shock tests can define the lower and upper boundaries of the threshold for the loss of coolable geometry of the reactor core during a LOCA.