Zirconium hydride phase mapping in Zircaloy-2 cladding after delayed hydride cracking

Hydrogen uptake in zirconium alloys is a major limiting factor of nuclear fuel cladding as subsequent hydride precipitation can lead to potential failure via delayed cracking (DHC). The specific mechanisms DHC have been focus earlier research, however there still no clear definition the resulting crystallography and sizes at various temperatures crack propagation. In this work, novel thermo-mechanical testing procedure was used induce radially propagating cracks thin-walled temperature range from 100 320 °C. Focused ion beam (FIB)- prepared lamellae were extracted samples containing arrested for synchrotron micro-beam X-ray diffraction (µXRD) mapping crystallographic phases. µXRD phase maps provided information about required cluster size that would fracture (less than 5 µm), i.e. critical size. Phase shows DHC-responsible hydrides primarily consist δ phase, with slightly increased ɣ/δ ratios lower temperatures. multilayer cladding, liner material significantly ɣ-hydride, while on average, δ-phase remains predominant. This work also highlights ɣ-hydride indeed stable which precipitate during propagation within inner cladding.