MILLSTONE NUCLEAR POWER STATION - UNIT #2: A SHORT CYCLE REWIND PROGRAMME

摘要

Many of the large liquid-cooled generators operating in power plants around the world were manufactured a quarter of a century or more ago by a variety of Original Equipment Manufacturers (OEMs). This aging fleet is increasingly susceptible to bar, end winding, and core vibration issues as well as stator bar liquid leaks, posing serious reliability and maintenance problems. Threats such as oil contamination, insulation damage, and age can adversely affect winding reliability. Leaks, bar or core failures that occur on machines operating at high voltage and high bar electromagnetic fields can cause forced outages, unplanned rewinds of the stator and field, and substantial contamination of the core and field, all of which can amount to considerable downtime of several months. The related losses involved in such circumstances can be significant. The Millstone Rewind Project, implemented by Northeast Utilities using General Electric's Short-Cycle Liquid-Cooled Rewind Program techniques, was designed to address these issues. The Millstone 2 Main Generator Stator Rewind Project was completed successfully in May 2000 during Millstone 2 Refueling Outage 13. This project consisted of the complete replacement of all the stator bars in the Millstone 2 main generator and installation of a new Main Generator Temperature Monitoring System in the Computer Room section of the Millstone 2 control room. The Main Generator Stator Rewind Project-the critical path activity throughout the outage-was completed in 35 days and seven hours, including tag, generator disassembly, rewind, and generator reassembly. By completing 65 hours ahead of the predicted 38-day schedule, the overall outage duration was reduced from the originally scheduled 45 days to an impressive 40 days and 20 hours, breaker to breaker. We believe this set a world record for a nuclear power plant outage duration, which included a main generator stator rewind. This paper, with its detailed reference materials, addresses all aspects of the decision process to implement a full stator rewind at Millstone. It also presents technical updates, decision analysis, and justification for the rewind, as well as details of GE's Short-Cycle Liquid-Cooled Rewind Program-a continuous improvement program with over 50 applications since 1996 on planned and unplanned, full and partial rewinds worldwide. Finally, this paper shares lessons learned and best practices that were the keys to successful critical path planning and outage execution as experienced by the outage team at Millstone.