Corrosion of structural materials in water and steam

In light water reactors stress corrosion is much more acute than in thermal power plants and should be minimized by a suitable choice of structural materials. Stress corrosion occurs in about 20% of nuclear power plants. The highest incidence has been recorded in AISI 304 steels. Lower incidence has been shown for Inconel 800 and practically none has been found in the ferritic 2.25Cr1Mo steel. Stress corrosion in operation is mainly due to deviations from the designed water regimen; stress corrosion was often observed in the preoperational stage. Stress corrosion mainly occurs in the presence of chlorides (22%), oxygen (18%), lye (11%), and due to other unknown impurities. Corrosion resistance tests were conducted in water and steam on steels used for the current manufacture of steam generators. Following preliminary interpolation (linear dependence) to 30 years, material losses in water and water steam under experimental conditions range within acceptable limits and may be tolerated in the steam generator design observing preset parameters. (Kr)