Materials Model Boiler Tests for the Babcock & Wilcox Once-Through Steam Generators

Two model test boilers simulated the operating conditions of the Babcock & Wilcox Company Oconee class once-through steam generators to test for materials-environment compatibility. Results of nearly seven years of operation show that a stress relief heat treatment [621°C (1150°F)/10 h] reduces the risk of stress corrosion cracking (SCC) of Alloy 600 steam generator tubes. The introduction of minor amounts of caustic contamination is also not likely to result in tube failures of properly heat treated tubes. Consequently, steam generators tubed with stress-relieved Alloy 600 and employing condensate-polished all volatile-treated water have little risk of tube failure by SCC and/or pitting corrosion.