American Electric Power (NYSE:AEP) utility Indiana Michigan Power said Jan. 3 that Unit 2 of the D.C. Cook nuclear plant in Bridgman, Michigan had completed an 89-day refueling and maintenance outage.
The company finished the regularly-scheduled outage at 7:20 p.m. on Jan. 2, the utility said in a news release. Unit 2 was listed at 23% power generation on Jan. 3 by the Nuclear Regulatory Commission (NRC).
In addition to refueling the reactor and performing regular maintenance and testing work, the outage was 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.
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 114 upgrade and replacement projects as part of the 20-year operating license extension granted by the NRC in 2005.
The baffle bolt inspections were previously planned for 2019 but were moved forward based on industry initiatives following the discovery of degraded baffle bolts at two plants this spring.
Ultrasonic inspection was performed on all 832 bolts and 201 bolts were replaced. Based on the inspections, AEP determined there was no impact on the safety of Unit 2 during the previous cycle of operation, AEP said.
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.
About 2,000 contracted workers supplemented the regular 1,200-person plant staff during the outage.
At full capacity, the 1,030-net MW Unit 1 and 1,077-net MW Unit 2 combined produce enough electricity for more than one and one half million average homes.
“Thanks to all our employees and local and regional craft workers for their safe and hard work during this longer than usual outage,” said Joel Gebbie, Senior Vice President and Chief Nuclear Officer. “We also appreciate the support of our families and the community as we work to secure the long-term viability and reliability of our plant,” Gebbie said.