Accelerated characterization of Zircaloy-4 and ATF cladding creep behavior in accident relevant conditions

Abstract

Accident tolerant fuel concepts represent valuable improvements to light-water reactors from both a safety and economic perspective. As accident tolerant fuel claddings are nearing maturity, it is vital that the mechanical behavior of the claddings is characterized during accident and off-normal conditions. Valuable thermomechanical data can help set performance and safety limits for further efficient operation of the current reactor fleet. However, characterization of cladding behavior during accident conditions is costly and time intensive. As such, an accelerated framework for characterizing high-temperature creep behavior has been developed utilizing digital image correlation. Creep testing of zircaloy-4 was evaluated at 650 °C and 700 °C to demonstrate the validity of this framework for future use on new cladding concepts. Discrete internal loading steps were utilized to recover creep behavior over a wide range of stresses from a single sample. Four tests in total were completed resulting in twenty stress-strain rate data points. The data was compared to conventional models of Zr creep behavior. It was found that the data agreed with models utilizing isotropic Hill parameters, possibly indicating effects of anisotropy were mitigated.