Remedial methods for intergranular attack of alloy 600 tubing. Volume 3. Boric acid and acetic acid remedial methods. Final report
An important cause of recent tube degradation in recirculating pressurized water reactor (PWR) steam generators with open tube/tubesheet crevices is intergranular attack (IGA) of alloy 600 tubing in the crevice region. The attack appears to occur on the hot leg tubing because of high concentrations of caustic species formed from remnants of past phosphate water treatment, combined with materials from inleakage from freshwater-cooled condensers. The concept of using neutralizers to modify the aggressiveness of the crevice environment was examined. It appears that this can be accomplished by neutralizing the caustic species with an acid. Two ways to apply the acid are by off-line flushing during plant shutdown and by on-line treatment during operation. The substance that appears to be most suitable for off-line flushing is acetic acid, with boric acid as a second choice. Concentrations should be in the range of from 1000 to 5000 ppM. The addition of 1000 to 5000 ppM of a non-ionic detergent in the flush solution should improve penetration of the crevice. Use of preflush lancing to remove sludge on the tubesheet will also help by reducing acid consumption. The requirements for materials to be used in on-line treatment are more stringent because of possible interaction with other components in the secondry system. Boric acid is the only substance that has operational experience. A series of tests are proposed to investigate the behavior of acetic acid and boric acid on tubesheet sludge, on tubesheet/support plate material, and on alloy 600/tubesheet couples. Similarly, areas of uncertainty of on-line treatment with boric acid are its effect on tubesheet/support plate materials and on the rest of the secondary system. 23 refs.
- Research Organization:
- Babcock and Wilcox Co., Alliance, OH (USA). Research and Development Div.
- OSTI ID:
- 5708583
- Report Number(s):
- EPRI-NP-4635-Vol.3; ON: TI86920389; TRN: 86-021995
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
36 MATERIALS SCIENCE
INCONEL 600
CREVICE CORROSION
INTERGRANULAR CORROSION
REACTOR MATERIALS
PWR TYPE REACTORS
STEAM GENERATORS
TUBES
ACETIC ACID
BORIC ACID
CORROSION INHIBITORS
WATER CHEMISTRY
ALLOYS
BOILERS
CARBOXYLIC ACIDS
CHEMICAL REACTIONS
CHEMISTRY
CHROMIUM ALLOYS
CORROSION
HYDROGEN COMPOUNDS
INCONEL ALLOYS
INORGANIC ACIDS
IRON ALLOYS
MATERIALS
MONOCARBOXYLIC ACIDS
NICKEL ALLOYS
NICKEL BASE ALLOYS
NIOBIUM ALLOYS
ORGANIC ACIDS
ORGANIC COMPOUNDS
REACTORS
VAPOR GENERATORS
WATER COOLED REACTORS
WATER MODERATED REACTORS
210200* - Power Reactors
Nonbreeding
Light-Water Moderated
Nonboiling Water Cooled
360105 - Metals & Alloys- Corrosion & Erosion