Investigation of resistance of nuclear fuel cladding to hydride cracking

Abstract

In this study hydride induced cracking was inves-tigated using specimens prepared from Zircaloy-4 fuel cladding materials. Temperature dependence of the de-layed 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 un-der constant loading and initial KI value of about 15 MPa√m. Crack growth velocity was determined at tem-perature range 144- 283°C. It was found that cracking ve-locity has Arrhenius type temperature dependence and in-creases up to 275 °C, at higher temperatures cracking rate sharply decreases. Delayed hydride cracking velocity de-pends on thermal treatment conditions of the cladding ma-terial, DHC rate is about 1.6 times higher in cold-worked than in stress-relieved material and no cracking was ob-served in recrystallized material.