Materials performance in operating pressurized water reactor steam generators

Journal Article · Mon Mar 01 04:00:00 EST 1976 · Nucl. Technol., v. 28, no. 3, pp. 348-355

OSTI ID:4092256

Weeks, J R

T he Inconel-600 tubing in operating pressurized water reactor (PWR) steam generators has developed leaks due to intergranular stress corrosion cracking or a general wastage attack, originating from the secondary side of the tubing. Corrosion has been limited to those areas of the steam generators where limited secondary coolant circulation and high heat flux have caused impurities to concentrate. Wastage or pitting attack has always been associated with local concentrations of sodium hydrogen phosphates, whereas stress corrosion has been associated with local concentration of sodium or potassium hydroxides. The only instance of stress corrosion originating from the primary side occurred on cold- worked tubing when hydrogen was not added to getter oxygen, and LiOH was not added to raise the pH of the primary coolant. All U. S. PWR manufacturers are now recommending an all-volatile treatment of the secondary coolant, whereas many plants operated until recently using a phosphate treatment. Experience in operating plants has shown, however, that removal of phosphate-rich sludge deposits is difficult, and that further wastage and/or intergranular stress corrosion can develop; the residual sodium phosphates gradually convert by reaction with corrosion product hydroxides to sodium hydroxide, which remains concentrated in the limited flow areas. Improvements in circulation patterns have been achieved by inserting flow baffles in some PWR steam generators. Inservice monitoring by eddy current techniques, as recommended in U. S. Nuclear Regulatory Commission Regulatory Guide 1.83, is useful for detecting corrosion- induced defects in the tubing, but irreproducibility in field examinations can lead to uncertainties in interpreting the results. (auth)

• Research Organization: Brookhaven National Lab., Upton, NY
• NSA Number: NSA-33-027968
• OSTI ID: 4092256
• Journal Information: Nucl. Technol., v. 28, no. 3, pp. 348-355, Journal Name: Nucl. Technol., v. 28, no. 3, pp. 348-355; ISSN NUTYB
• Country of Publication: United States
• Language: English

Related Subjects

*PWR TYPE REACTORS-- STEAM GENERATORS
*STEAM GENERATORS-- MATERIALS
210200* --Nuclear Power Plants--Power Reactors
Non- Breeding
Light-Water Moderated
Non-Boiling Water Cooled
INCONEL 600
LEAKS
N77200* --Reactors--Power Reactors
Non-breeding
Light- water Moderated
Non-boiling Water-cooled
PERFORMANCE
PITTING CORROSION
STRESS CORROSION
TUBES
WATER CHEMISTRY