Effects of Hydrogen on Stress Corrosion Crack Growth Rate of Nickel Alloys in High-Temperature Water

Stress corrosion cracking (SCC) of Alloy 600 (UNS N06600) and Alloys 182 (UNS W86182), 132 (UNS W86132), and 82 (UNS N06082) weld metals in high-temperature water is important because these materials are used widely in the pressurized water reactor (PWR) coolant system. Plant experience indicates that SCC will steadily increase as plants age without effective mitigation. Because there is a peak in crack growth rate vs. dissolved H2, adjusting the dissolved hydrogen concentration represents a significant opportunity for SCC mitigation in PWR primary water. The effects of lithium and boron concentrations, the associated pH at temperature, are observed to have little effect on crack growth rate.