The Unit 2 reactor at the Cook nuclear power plant in Bridgman, MI, is up and running after being down since late September for a planned refueling and maintenance outage.

Indiana Michigan Power’s Cook plant completed its refueling at 7:20 p.m. Monday allowing its Unit 2 reactor to reconnect to the transmission grid.

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In addition to refueling the reactor and performing regular maintenance and testing work, the 89-day outage ended up 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 projects.

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The $250 million turbine replacement has been in the planning stages for more than five years.

Originally, plans called for the reactor to be gaining in power and connected to the electric grid by late December.

However, an unexpected snag occurred as problems with defective fuel pump injectors for emergency diesel generators used as backup power supply for Units 1 and 2 ended up discovered, plant spokesman Bill Schalk said.

“That caused about a week delay from the schedule as we were hoping to be up around Christmas Eve, but it was a longer outage because of the baffle bolts and the turbine,” Schalk said.

The baffle bolt inspections were previously on tap for 2019, but that plan moved forward based on industry initiatives following the discovery of degraded baffle bolts at two plants last spring.

Plant workers performed ultrasonic inspection on all 832 bolts, and 201 bolts ended up replaced. Based on the inspections, AEP determined there was no impact on the safety of Unit 2 during the previous cycle of operation.

Cook’s Life Cycle Management includes 114 upgrade and replacement projects as part of the 20-year operating license extension granted by the Nuclear Regulatory Commission in 2005.

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 assisted the plant’s 1,200 full-time employees during the outage.

At full capacity, both unit reactors at Cook combined are capable of producing enough electricity to power more than 1.5 million homes.

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