Denting of Inconel steam generator tubes in pressurized water reactors. Third informal report

Technical Report · Mon Aug 01 04:00:00 EDT 1977

OSTI ID:6812195

van Rooyen, D; Weeks, J R

The recent plant operating experience and laboratory test results on the phenomenon of denting in recirculating PWR steam generators is reviewed. Although denting was first reported only in plants that were converted from phosphate to AVT, it has now also been observed in plants still on phosphate, as well as in some that started on AVT. In some units, slightly abnormal eddy current signals have been observed at the top of the tube sheets. The degree of denting in operating steam generators may be related to the levels and duration of chloride inleakage. Chloride, however, is not the only active ingredient, and does not seem to give denting until local acid conditions arise; consequently, it may be necessary for soluble copper and/or nickel ions to be present to promote the denting reaction. Chloride concentrations in actively corroding crevices can increase by several orders of magnitude over the bulk coolant. It is thus difficult to develop a basis for Cl/sup -/ specifications for secondary water. Maintaining Cl/sup -/ low enough to prevent denting may be unmanageable without full flow condensate demineralization in coastal plants with copper alloy condensors and feedwater lines. Cathodic depolarization by oxidizing species are thought to promote the formation of acid chlorides in crevices and trigger the denting reactions; some ions may also catalyze the rapid formation of magnetite. These, and other mechanistic aspects of denting are discussed. The implications of the Inconel 600 tube defects at Ginna in non-dented areas, originating from the primary side, are also discussed.

• Research Organization: Brookhaven National Lab., Upton, N.Y. (USA)
• DOE Contract Number: EY-76-C-02-0016
• OSTI ID: 6812195
• Report Number(s): BNL-NUREG-23219
• Country of Publication: United States
• Language: English

Related Subjects

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS
210200* -- Power Reactors
Nonbreeding
Light-Water Moderated
Nonboiling Water Cooled
ALLOYS
BOILERS
CHEMICAL REACTIONS
CHROMIUM ALLOYS
CORROSION
CORROSION PRODUCTS
CORROSION PROTECTION
DEFORMATION
INCONEL ALLOYS
NICKEL ALLOYS
NICKEL BASE ALLOYS
PWR TYPE REACTORS
REACTORS
STEAM GENERATORS
TUBES
VAPOR GENERATORS
WATER CHEMISTRY
WATER COOLED REACTORS
WATER MODERATED REACTORS