Cook 2 nuclear unit begins extended refueling outage

The D.C. Cook 2 nuclear unit operated by American Electric Power (NYSE:AEP) utility Indiana Michigan Power began its 22nd refueling outage on Oct. 3.

The refueling and maintenance outage will include a $250m turbine replacement project, the utility said in a news release.

During the 18-month fuel cycle, the unit is projected to have generated 13.5 million megawatthours (MWh) of electricity at a capacity factor of 99.4%. Unit 2 has operated at effective full power for the last five fuel cycles dating back to May of 2009. Cook Unit 1 remains at 100% power, the utility said in a news release.

In addition to refueling the reactor and performing regular maintenance and testing work, the outage will be extended due to the replacement of the main turbine and the inspection and replacement of baffle bolts, which support internal components of the reactor vessel.

Specific outage duration is considered proprietary information, but the outage is expected to be completed in the fourth quarter of this year.

Replacement of the high-pressure turbine and all three low-pressure turbines is the largest of Cook’s Life Cycle Management (LCM) projects. The $250m turbine replacement has been in the planning for more than five years and it was known that it would extend this outage.

LCM includes 117 upgrade and replacement projects as part of the 20-year operating license extension granted by the Nuclear Regulatory Commission in 2005.

AEP will accelerate baffle bolt inspections previously planned for 2019 based on industry initiatives that commenced following the discovery of degraded baffle bolts at two plants this spring. Any degraded bolts will be replaced and it’s likely that additional bolts will be proactively replaced this outage.

The baffle bolts hold the baffle plates in place which direct water flow through the fuel assemblies in the reactor. Similar bolt failures have occurred previously in the industry and specialized repair tools and existing safety analyses are used to resolve the issue. The identified causes of the failed bolts were considered in the replacement bolt design and repair. Additional baffle bolt inspections and replacements, and a potential design change to minimize stress on baffle bolts, may also take place in subsequent outages for both Cook units.

Another of the LCM projects this outage is replacement of two 40-ton safety-related heat exchangers. Other major projects include emergency power cable and battery replacements, pump and valve overhauls and improvements to the nuclear fuel handling equipment.

About 2,500 contracted workers will supplement the regular 1,200-person plant staff leading up to and during the outage. About 500 of those workers will be dedicated to the turbine replacements alone. More than 15,500 maintenance, inspection and equipment modification job activities totaling almost 400,000 work-hours are scheduled for two daily 12-hour work shifts.

At full capacity, the 1,030-MW (net) Unit 1 and 1,077-MW (net) Unit 2 combined produce enough electricity for more than one and one half million average homes. The two pressurized water reactors (PWRs) are located in Bridgman, Michigan.

About Wayne Barber 4201 Articles
Wayne Barber, Chief Analyst for the GenerationHub, has been covering power generation, energy and natural resources issues at national publications for more than 20 years. Prior to joining PennWell he was editor of Generation Markets Week at SNL Financial for nine years. He has also worked as a business journalist at both McGraw-Hill and Financial Times Energy. Wayne also worked as a newspaper reporter for several years. During his career has visited nuclear reactors and coal mines as well as coal and natural gas power plants. Wayne can be reached at