Unveiling Damage Mechanisms of Chromium-Coated Zirconium-Based Fuel Claddings

Coated nuclear fuel claddings offer a promising, near-term solution to address the demand for next-generation, accident-tolerant fuel systems and possess superior mechanical properties and greater oxidation resistance compared to current cladding technology, allowing for improved performance during beyond design-basis accident conditions. Here, we unveil the room temperature (23 °C) and high temperature (315 °C) failure mechanisms of chromium-coated zirconium alloys using a novel mechanical test rig coupled with in-situ three-dimensional digital image correlation and acoustic emissions sensing to monitor spatial strain and crack initiation / propagation during cladding expansion. Ex-situ scanning electron microscopy was used to characterize crack propagation at various levels of strain and temperature. Axial cracking along the full circumference of the room temperature samples was observed, while angled cracks along the surface were observed in the high temperature samples. Through-thickness cracking was observed in both room temperature and high temperature samples. The differing fracture mechanisms observed between room temperature and high temperature samples will carry significant implications for their use in reactor environments.