Influences of Stress Intensity Factor and Dissolved Hydrogen on the Fatigue Crack Growth Behavior of Low-Alloy Steel in Boiling Water Reactors

Environmentally assisted cracking (EAC) of low-alloy steels exposed to high-temperature water in a simulated boiling water reactor (BWR) environment was found to be dependent upon the stress intensity range (ΔK) of the specimens and the dissolved hydrogen concentration. Whether the load frequency was high or low, the crack propagation rate increased as the stress intensity range (ΔK) increased under the same water quality and loading conditions. In addition, the electrochemical corrosion potential (ECP) of low-alloy steel in high-temperature pure water is closely related to the amounts of dissolved oxygen and hydrogen in the water. It was observed that even dissolved low concentrations of hydrogen, which lowered the ECP, could effectively suppress the crack growth rate (CGR). Many CGR data from this study were comparable with those obtained from some well-known CGR prediction models for BWR environments, except in the hydrogen water chemistry (HWC) condition. However, the current CGR data with a low loading frequency were not bounded by the Eason model.