Effect of hydride re-orientation and hydride rim on fracture energy of Zircaloy-4 cladding

Some phenomena, such as hydride rim and hydride re-orientation, can occur in SNF claddings and they can worse the integrity of the claddings more than uniformly precipitated hydrides. In this study, hydrogen charging and hydride re-orientation treatment were implemented to simulate SNF claddings and ring compression tests were adopted as a test method to evaluate the fracture energy of claddings which shall be subjected to shock loads during transportation. Then, effects of hydride re-orientation and hydride rim on fracture energy were analyzed based on the RCT results. RCTs were conducted using uniform hydride specimens and hydride rim specimens treated hydride re-orientation in 90-150 MPa at a temperature ranges from RT to 200 degrees C. Mechanical properties of SNF claddings were evaluated on two parameters, The fracture energy/area at RT, 100 degrees C and 150 degrees C decreases with an increase in the RHCF. Radial hydride can be an important factor to evaluate facture energy of claddings. With high hoop stress (e.g. U1, U2, R1, and R2), claddings can be brittle even in 150-200 degrees C. Claddings with hydride rim can be ruptured by low external energy although cladding hoop stress is low.