Model boiler testing to evaluate inhibitors for caustic induced stress corrosion cracking of Alloy 600 tubes
- Commissariat a l`Energie Atomique, Hague (France)
- Electric Power Research Inst., Palo Alto, CA (United States)
- Dominion Engineering Inc., McLean, VA (United States)
A series of model boiler tests, using a mixture of precracked and non-precracked (virgin) tube-to-tube support plate intersections was performed. The testing supported the qualification of inhibitors for mitigating the secondary side corrosion of alloy 600 steam generator tubes. Many utilities suspect that the caustic impurities come from the feedwater. Candidate inhibitors included boric acid (as a reference), cerous acetate, and two forms of titanium dioxide: a laboratory produced titania-silica sol-gel, and manometer sized anatase The latter was combined with a 150 C pre-soaking with a titanium lactate, and was tested with and without a zeta potential treatment by sodium aluminate. Effectiveness of boric acid to prevent and retard caustic induced intergranular corrosion was confirmed in all crevice configurations (open and packed). The cerous acetate treatment multiplied by two to four the time necessary to detect a primary-to-secondary leak on virgin tubes, and reduced the propagation rate on precracked tubes. Cerium was found intimately mixed, as cerianite, with the free span and crevice deposits, when the crevices were sufficiently accessible. Due to its very low solubility and large particle size, the titania-silica sol-gel was unable to penetrate the crevices and had no effect on the degradation process. The nanometric particle size titania treatment and/or the preceding soaking with soluble titanium lactate drastically increased the titanium concentration in free span and open crevice deposit (with no added sodium aluminate, titania reacted with magnetite to form ilmenite) and showed undeniable capacity to prevent tubing degradation. Its effectiveness, in the case of packed crevices and for arresting cracks, was not so conclusive.
- OSTI ID:
- 203803
- Report Number(s):
- CONF-950816-; ISBN 1-877914-95-9; TRN: 96:009769
- Resource Relation:
- Conference: 7. international symposium on environmental degradation of materials in nuclear power plants: water reactors, Breckenridge, CO (United States), 6-10 Aug 1995; Other Information: PBD: 1995; Related Information: Is Part Of Seventh international symposium on environmental degradation of materials in nuclear power systems -- Water reactors: Proceedings and symposium discussions. Volume 1; Airey, G.; Andresen, P.; Brown, J. [eds.] [and others]; PB: 664 p.
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
21 NUCLEAR POWER REACTORS AND ASSOCIATED PLANTS
CORROSION INHIBITORS
PERFORMANCE TESTING
INCONEL 600
STRESS CORROSION
CRACK PROPAGATION
STEAM GENERATORS
TUBES
CORROSION PROTECTION
PWR TYPE REACTORS
MITIGATION
INTERGRANULAR CORROSION
SECONDARY COOLANT CIRCUITS
EXPERIMENTAL DATA
ADDITIVES