New options for improved steam generator U-bend integrity
Primary-side intergranular stress corrosion cracking (IGSCC) has been noted in the U-bend region of first- and second-row Alloy 600 tubes in pressurized water reactor recirculating steam generators. The cracks have been found primarily at the apex and near the tangents of the bends on the extrados (outside bend radius) and in the sides near the small radius of the curvature portion of the distorted tube. During fabrication, the tubes were bent without stress relief. High residual strains are therefore present in these tube sections. Further, laboratory tests have shown Inconel 600 material to be susceptible to IGSCC at nuclear steam supply system operating temperatures. Although the cracking mechanism is generally understood, the tight radius bend, the tube ovality, and the complications of working in a radioactive steam generator make inspection and repair of these regions challenging. Babcock and Wilcox has initiated three programs to attack the U-bend cracking problems: applying rotating probe technology for better tube examinations, stress relieving the tubes to retard IGSCC, and removing plugs to return previously plugged tubes to service. Collectively, these three programs provide a valuable tool to keep the small radius U-bend tubes of commercial nuclear systems in service.
- OSTI ID:
- 6981904
- Report Number(s):
- CONF-8711195-
- Journal Information:
- Trans. Am. Nucl. Soc.; (United States), Journal Name: Trans. Am. Nucl. Soc.; (United States) Vol. 55; ISSN TANSA
- Country of Publication:
- United States
- Language:
- English
Similar Records
Corrosion test qualification for in situ stress relief of recirculating steam generators' U-bends
Residual and applied stress analysis of an alloy 600 row 1 U-bend: Final report
Related Subjects
210200* -- Power Reactors
Nonbreeding
Light-Water Moderated
Nonboiling Water Cooled
ALLOYS
BOILERS
CHEMICAL REACTIONS
CHROMIUM ALLOYS
COOLING SYSTEMS
CORROSION
CRACKS
EDDY CURRENT TESTING
ELECTROMAGNETIC TESTING
ENERGY SYSTEMS
FABRICATION
INCONEL 600
INCONEL ALLOYS
INSPECTION
INTERGRANULAR CORROSION
IRON ALLOYS
MATERIALS TESTING
NICKEL ALLOYS
NICKEL BASE ALLOYS
NIOBIUM ALLOYS
NONDESTRUCTIVE TESTING
PERFORMANCE
PLUGGING
PRIMARY COOLANT CIRCUITS
PWR TYPE REACTORS
REACTOR COMPONENTS
REACTOR COOLING SYSTEMS
REACTORS
RELAXATION
REPAIR
RESIDUAL STRESSES
STEAM GENERATORS
STRESS CORROSION
STRESS RELAXATION
STRESSES
TESTING
TUBES
VAPOR GENERATORS
WATER COOLED REACTORS
WATER MODERATED REACTORS