The Mechanical Response Evaluation of Advanced Claddings During Proposed Reactivity Initiated Accident Conditions

This study investigates the failure mechanisms of advanced oxidation resistant FeCrAl nuclear fuel cladding at high-strain rates, similar to conditions characteristic of design basis reactivity initiated accidents (RIAs). During a postulated RIA, the nuclear fuel cladding may be subjected to complex loading which can cause multiaxial strain states ranging from plane-strain to equibiaxial tension. To achieve those accident conditions, the samples were deformed by the expansion of high strength Inconel alloy tube under pre-specified pressure pulses, simulating strains rates occurring in a postulated RIA. The mechanical response of the advanced claddings, in the unirradiated state with ample ductility, was compared to that of hydrided zirconium-based nuclear fuel cladding. The hoop strain evolution pulses were collected in situ; the permanent diametral strains of both accident tolerant fuel (ATF) claddings and the current nuclear fuel alloys were determined after rupture. Both zirconium-based alloys and FeCrAl alloys exhibited ductile behavior. FeCrAl model alloys without microstructural control and strengthening mechanism were used in this demonstration study that showed reduced diametral strain (less than 0.15) compared to the diametral strain for the unirradiated zirconium-based alloy (approximately 0.2).