Virtually all of the 17,000 tubes in the two units were deteriorating, with 2500 plugged and 5000 sleeved. In the early 1980s, pitting problems surfaced in the steam generator tubing by the mid eighties, tube corrosion had reached an unacceptable level. This was the experience at Unit 2 of Millstone nuclear station, which features an 870-MW pressurized-water reactor (PWR) with two nuclear recirculating steam generators. In selecting replacements for major powerplant components, a fresh approach can be advantageous-even when complex nuclear components are involved. OSTI Identifier: 7145843 Report Number(s): EPRI-NP-4831 ON: TI87920091 TRN: 86-038166 Resource Type: Technical Report Country of Publication: United States Language: English Subject: 21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS 36 MATERIALS SCIENCE MILLSTONE-2 REACTOR STEAM GENERATORS CHROMIUM STEELS COPPER INCONEL 600 IRON NICKEL NUCLEAR POWER PLANTS PH VALUE PITTING CORROSION REACTOR MATERIALS REACTOR OPERATION TUBES WATER CHEMISTRY ALLOYS BOILERS CHEMICAL REACTIONS CHEMISTRY CHROMIUM ALLOYS CORROSION ELEMENTS ENRICHED URANIUM REACTORS INCONEL ALLOYS IRON ALLOYS IRON BASE ALLOYS MATERIALS METALS NICKEL ALLOYS NICKEL BASE ALLOYS NIOBIUM ALLOYS NUCLEAR FACILITIES OPERATION POWER PLANTS POWER REACTORS PWR TYPE REACTORS REACTORS STEELS THERMAL POWER PLANTS TRANSITION ELEMENTS VAPOR GENERATORS WATER COOLED REACTORS WATER MODERATED REACTORS 210200* - Power Reactors, Nonbreeding, Light-Water Moderated, Nonboiling Water Cooled 360105 - Metals & Alloys- Corrosion & = , It also indicates the need to minimize accumulation of copper and iron oxides and of acid-forming salts in the steam generators.Īuthors: Daniel, P L Harper, S L Publication Date: Wed Oct 01 00:00: Research Org.: Babcock and Wilcox Co., Alliance, OH (USA). This work corroborates the postulated pitting mechanism and suggests a mechanism of formation for the observed wastage bands. Local solute concentrations of 0.001 to 0.1 molar are consistent with the postulated pH. Pitting occurs in areas where reduction of copper oxides raises the Alloy 600 surface potential into the passive range. The wastage band near the tubesheet is attributed to active dissolution of Alloy 600, which occurs at low potentials.

Indications are that the pH within the pits and wastage areas ranges from 1 to 4 - the higher pH occurs at the tube surface and in pits near the tubesheet the lower pH occurs in pits away from the tubesheet. They were used to analyze local corrosive conditions and corrosion processes that occur in the steam generators. The diagrams were constructed using new thermodynamic data. Corrosion products identified on Alloy 600 tubes pulled from the Millstone Unit 2 nuclear steam generator were compared to phase fields of appropriate Pourbaix diagrams.

Copper pourbaix diagram