SUSCEPTIBILITY OF LOW-ALLOY CARBON-STEEL TO FITTING AND STRESS-CORROSION CRACKING IN STEAM-GENERATOR CONDITIONS

The susceptibility of ASTM A302, grade B steel (UNS K12022) to stress corrosion cracking (SCC) and pitting was examined through modeling of different stages of operation of the steam generator in a nuclear powe r plant Effects of temperature, dissolved oxygen (DO) content, and dir ection of loading were studied The steel was found to be very suscepti ble to pitting and SCC at all tested temperatures (100 degrees C to 26 0 degrees C), especially when the DO level was > 50 ppb. Fitting and S CC were often associated with the presence of sulfide inclusions. The short transverse direction was more susceptible to SCC than the longit udinal direction. The presence of a weld region was not found to enhan ce susceptibility to cracking or pitting.