Evaluation of intergranular attack on Alloy 600: Volume 2, Effectiveness of boric acid: Final report

Technical Report · Tue Dec 01 00:00:00 EST 1987

OSTI ID:5536398

Hermer, R E; Wolfe, C R

The effect of boric acid applied on-line and via crevice flushing was evaluated in this program as a remedial action for intergranular attack on mill annealed Alloy 600 steam generator tubing in tubesheet and support plate crevices. Single tube model boilers were used to simulate the full length of a steam generator tubesheet crevice and the support plate crevices at hot leg conditions. The tubesheet crevices had preloaded inventories of 10% sodium hydroxide/2.5% sodium sulfate solution. All of the crevices were exposed to on-line additions of 0.1 ppM hydroxide and 0.04 ppM sulfate as the sodium salts. These baseline conditions caused pre-existing IGA beneath eccentrically mounted support plates to increase in depth at a rate of 2.40 ..mu..m/day. In the tubesheet crevices the pre-existing IGA increased in depth at a rate of 1.6 ..mu..m/day. The virgin mill annealed tubing in the tubesheet crevice developed IGA at a rate of 0.73 ..mu..m/day during the final 60 days of the 90 day test. The first 30 days were an incubation period during which no IGA occurred. The results of this work suggest that boric acid can inhibit IGA on unattacked tubing when applied continuously at the field specifiation of 5 to 10 ppM in the blowdown. It can also slow down propagation of pre-existing IGA if present in the proper ratio (which requires adequate treatment levels) and if it can access the corrosion sites. Corrosion may progress in areas where boric acid is not able to penetrate in sufficient excess to the corrodent present. 10 refs., 85 figs., 39 tabs.

• Research Organization: Westinghouse Electric Corp., Pittsburgh, PA (USA). Steam Generator Technology Div.
• OSTI ID: 5536398
• Report Number(s): EPRI-NP-4978-Vol.2; ON: TI88920139
• Country of Publication: United States
• Language: English

Related Subjects

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS
36 MATERIALS SCIENCE
INCONEL 600
CORROSION INHIBITORS
INTERGRANULAR CORROSION
STRESS CORROSION
PWR TYPE REACTORS
STEAM GENERATORS
BORIC ACID
PROGRESS REPORT
SECONDARY COOLANT CIRCUITS
TUBES
WATER CHEMISTRY
ALLOYS
BOILERS
CHEMICAL REACTIONS
CHEMISTRY
CHROMIUM ALLOYS
COOLING SYSTEMS
CORROSION
DOCUMENT TYPES
ENERGY SYSTEMS
HYDROGEN COMPOUNDS
INCONEL ALLOYS
INORGANIC ACIDS
IRON ALLOYS
NICKEL ALLOYS
NICKEL BASE ALLOYS
NIOBIUM ALLOYS
REACTOR COMPONENTS
REACTOR COOLING SYSTEMS
REACTORS
VAPOR GENERATORS
WATER COOLED REACTORS
WATER MODERATED REACTORS
210200* - Power Reactors
Nonbreeding
Light-Water Moderated
Nonboiling Water Cooled
360105 - Metals & Alloys- Corrosion & Erosion