Causes of denting. Volume 2. Laboratory test results. Final report
Denting is the deformation of the alloy 600 heat transfer tubes at tube-tube support plate intersections in some nuclear steam generators. The purpose of this study was to review the results of all Westinghouse dent-related laboratory testing in order to derive correlations between corrosion rates and chemistry, temperature, heat flux, crevice condition, and support plate material. Chemistry considerations are the most significant of these parameters and involve the definition of the level of acid chloride in the crevice. Consideration of the relationship between this concentrated solution and the more dilute bulk environment is also provided. The principal effect of heat transfer is to concentrate, within crevices, nonvolatile contaminants that are present in the bulk. Correlation of denting with heat flux level is influenced by bulk chemistry or local thermohydraulics and thus are difficult to attribute directly to heat flux. Denting increased with temperature. Crevice condition encompassed three variables: width, packing, and shape. A minimum width was found in both isothermal and heat transfer tests, below which denting or bulging was negligible or nonsustainable beyond a marginal extent. The quatrefoil crevice shape required higher heat flux than the drilled shape to produce denting on A285 carbon steel material. Pre-packing crevices with corrosion product oxides did not profoundly alter the denting mechanism, but was adopted mainly to optimize consistency of results. The resistance to denting of different support materials was found to increase with increasing chromium content of the alloy, and 405 SS, in either the drilled or quatrefoil configuration, resisted denting.
- Research Organization:
- Westinghouse Electric Corp., Pittsburgh, PA (USA). Nuclear Technology Div.
- OSTI ID:
- 6923548
- Report Number(s):
- EPRI-NP-3275-Vol.2; ON: TI84920420
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
210200* -- Power Reactors
Nonbreeding
Light-Water Moderated
Nonboiling Water Cooled
ALLOYS
BOILERS
CARBON STEELS
CHEMICAL REACTIONS
CHEMISTRY
CHROMIUM ALLOYS
CHROMIUM STEELS
CORRELATIONS
CORROSION
CORROSION DENTING
CORROSION RESISTANT ALLOYS
CREVICE CORROSION
DEFORMATION
ENERGY TRANSFER
HEAT TRANSFER
INCONEL 600
INCONEL ALLOYS
IRON ALLOYS
IRON BASE ALLOYS
NICKEL ALLOYS
NICKEL BASE ALLOYS
NIOBIUM ALLOYS
PWR TYPE REACTORS
REACTORS
STAINLESS STEEL-405
STAINLESS STEELS
STEAM GENERATORS
STEELS
TUBES
VAPOR GENERATORS
WATER CHEMISTRY
WATER COOLED REACTORS
WATER MODERATED REACTORS