Hydride effect on crack instability of Zircaloy cladding

•Radial hydrides near the crack tip had a significant effect on crack propagation.•For radial hydrides off the crack line vertically, the effect on crack propagation was notably reduced.•The longer hydride platelet resulted in a remarkable effect on crack propagation.•A long split in the radial hydride precipitate would enhance crack propagation.•The presence of circumferential hydride among radial hydrides may play an important role in crack propagation.

A methodology was proposed to investigate the effect of hydride on the crack propagation in fuel cladding. The analysis was modeled based on an outside-in crack with radial hydrides located near its crack tip. The finite element method was used in the calculation; both stress intensity factor KI and J integral were applied to evaluate the crack stability. The parameters employed in the analysis included the location of radial hydride, hydride dimensions, number of hydrides, and the presence of circumferential hydride, etc. According to our study, the effective distance between a radial hydride and the assumed cladding surface crack for the enhancement of crack propagation proved to be no greater than 0.06 mm. For a hydride not on the crack line, it would induce a relatively minor effect on crack propagation if the vertical distance was beyond 0.05 mm. However, a longer hydride precipitate as well as double radial hydrides could have a remarkable effect on crack propagation. A combined effect of radial and circumferential hydrides was also discussed.