Stress Corrosion Crack Initiation and Growth and Formation of Pellet-Clad Interaction Defects

Abstract

The critical events leading to stress corrosion failure of fuel rods are poorly understood. The aim of the present work is to acquire data on stress corrosion cracking (SCC) initiation and crack growth and to use these data for improving our understanding of fuel rod failures. Crack growth has been studied as a function of stress intensity by means of cladding specimens with fatigue precracks of different sizes. The SCC growth rate was found to increase with the ninth power of the stress intensity. Smooth SCC specimens have been studied under constant load and under constant strain rate conditions. By applying the crack growth functions (determined by experiments with the fatigue precracked specimens), the times spent to propagate a crack and to initiate a crack as a function of stress have been deduced. The effect of irradiation on the SCC properties has been investigated with specimens irradiated in Halden boiling water reactor (HBWR).