Maintenance Strategies for Incoloy-800 Heat Exchangers Cooled by Service Water

Abstract

About 4% of the total production losses experienced by Ontario Hydro's nuclear generating stations has been attributable to heat exchanger (HX) maintenance. One of the most significant problems has been the failure of the Pickering Nuclear Generating Station B (PNGS-B) Incoloy-800 (1-800) tubed moderator HX's due to corrosion under service water deposits. Darlington NGS (DNGS) shutdown cooling HX's and Unit 1 and 2 moderator HX1s plus all Bruce NGS (BNGS) moderator HX1s are also tubed with 1-800 and cooled by service water. A strategy consisting of tube bundle replacement combined with preventive maintenance has been developed to minimize the impact of 1-800 corrosion.