Hydrides Formation From Fuel Cladding Corrosion and Influence of Hydrides on Mechanical Behavior

Corrosion of zirconium-based new cladding material exposed to reactor coolant water during nuclear reactor operations could lead to hydrogen absorption into the material and subsequently precipitation as hydrides during extended storage. Depending on size, distribution, and orientation, these hydrides may lead to premature fracture, as a result of hydride embrittlement or delayed hydride cracking. The work described in this paper used cathodic charging followed by annealing to prepare hydrided Zircaloy-2 three-point-bent beam specimens. The hydrided specimens were studied using a loading stage inside a scanning electron microscope chamber to investigate the critical stress levels required to cause hydride reorientation and to characterize the fracture resistance after hydride reorientation. The results showed that the absorbed hydrogen content in the bulk material can be adjusted by controlling the cathodic charging conditions and annealing temperature. The reoriented hydrides reduced the fracture resistance of the Zircaloy-2 material. The resulting stress intensity factor-resistance curves for Zircaloy-2 with reoriented hydrides are lower than those of Zircaloy-2 without hydrides.