Investigation of resistance of nuclear fuel cladding to hydride cracking

In this study hydride induced cracking was investigated using specimens prepared from Zircaloy-4 fuel cladding materials. Temperature dependence of the delayed hydride cracking (DHC) rate and the influence of heat treatment on hydride cracking was evaluated. After adding about 200 wt-ppm of hydrogen to the samples DHC velocity was determined on fatigue precracked specimens using pin-loading tension technique. Tests were done under constant loading and initial K-I value of about 15 MPa root m. Crack growth velocity was determined at temperature range 144- 283 degrees C. It was found that cracking velocity has Arrhenius type temperature dependence and increases up to 275 degrees C, at higher temperatures cracking rate sharply decreases. Delayed hydride cracking velocity depends on thermal treatment conditions of the cladding material, DHC rate is about 1.6 times higher in cold-worked than in stress-relieved material and no cracking was observed in recrystallized material.