Corrosion of Palo Verde 2 upper bundle steam generator tubing

Book · Sun Dec 31 04:00:00 EST 1995

OSTI ID:203822

Magee, T P; Molkenthin, J P; Hall, J F ^[1]; Melton, M A; Sachs, D E; Sweeney, K M ^[2]; Begley, J ^[3]

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1. ABB Combustion Engineering, Windsor, CT (United States)
2. Arizona Public Service Co., Tonopah, AZ (United States)
3. Packer Engineering, Pittsburgh, PA (United States)

Palo Verde Unit-2 (PV-2) has experienced degradation in the upper bundle region of some of its Alloy 600 steam generator (SG) tubes. Arizona Public Service (APS) initiated several mitigating actions, including a 1994 chemical cleaning to remove tube deposits. Eddy current tests (ECT) conducted after chemical cleaning showed an increase in the number of indications. To detail the bend region indications, APS elected to remove the hot leg bend portion of 21 tubes for laboratory examination. The examination showed that the degradation mode was outside diameter initiated intergranular attack (IGA) and intergranular stress corrosion cracking (IGSCC). The most severe corrosion occurred beneath ridge-like deposits, although shallow IGA was discovered on large areas of free-span tubing. In some cases, degradation was associated with scratches or gouges on the tubes. Some wear was apparently caused by periodic tube-to-tube contact. Degradation was found in tubing with both poor and partial correspondence between grain boundaries and carbides. The chemical conditions that caused the tube degradation were likely neutral to alkaline solutions containing residual sulfur (sulfide) species. The burst strength of all tubes tested significantly exceeded Regulatory Guide 1.121 requirements. These results confirmed past PV-2 tube corrosion examination results.

• OSTI ID: 203822
• Report Number(s): CONF-950816--; ISBN 1-877914-95-9
• Country of Publication: United States
• Language: English

Related Subjects

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS
36 MATERIALS SCIENCE
CORROSION
CRACK PROPAGATION
EXPERIMENTAL DATA
INCONEL 600
INTERGRANULAR CORROSION
MECHANICAL PROPERTIES
MITIGATION
NONDESTRUCTIVE TESTING
PALO VERDE-2 REACTOR
STEAM GENERATORS
TUBES
WEAR