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Major Upgrades at Constellation Nuclear Stations Ensure Carbon-Free Electricity for 15 Million This Summer

Over 13,000 workers supported maintenance projects during spring refueling outages to keep power supplied 24/7 during hot summer months and beyond

Over 13,000 workers performed technology upgrades and equipment maintenance during six refueling outages at Constellation nuclear plants this spring, investments that will prepare the plants for the hot summer months ahead. The cutting-edge upgrades and preventive maintenance will ensure Constellation’s nuclear fleet, which serves 15 million American homes and businesses, will have access to safe, affordable, carbon-free electricity this summer to help combat any periods of high heat or humidity.

During the refueling outages, workers replaced or refurbished dozens of pumps and motors, performed quality assurance inspections on reactor and fuel components, and completed tens of thousands of other technical tasks to ensure the power plants provide uninterrupted carbon-free electricity for up to 24 straight months.

“Constellation is helping accelerate this country’s transition to a carbon-free future and it begins with our zero emissions nuclear fleet running nonstop through the summer,” said Joe Dominguez, CEO of Constellation. “We met our commitment to operational excellence last winter by keeping our plants running throughout the cold months despite challenging weather conditions. Our investments in the plants this spring will help us maintain that level of performance during the upcoming summer months, as the climate crisis continues to produce extremely hot weather.”

This summer, nuclear reliability could be especially helpful in moderating electricity prices for Illinois customers. Constellation’s 24/7 carbon-free baseload nuclear power displaces generation from fossil-fuel plants that may experience further spikes in gas and oil costs. This is in addition to the $1 billion credit Constellation’s nuclear plants are projected to deliver for northern Illinois ratepayers as a result of the Climate & Equitable Jobs Act passed last year.

The refueling outages would not be possible without support from thousands of skilled electricians, pipefitters, welders, carpenters, laborers, steamfitters and other trades people on site performing thousands of inspections, tests and maintenance activities that cannot be done while the unit is online. Along with replacing about one-third of the fuel in each reactor, workers completed other major projects during the nuclear outages this spring, including:

  • In Illinois, workers at Quad Cities Unit 2 performed an overhaul and inspection of the turbine on one of the redundant core cooling systems; a full technical inspection of the Byron Station Unit 2 main generator; and a comprehensive inspection of two reactor recirculation flow control valves at LaSalle County Generating Station.
  • In the east, workers at Calvert Cliffs Station in Maryland replaced the Unit 1 main generator connections. At Limerick Station in southeastern Pennsylvania, technical experts performed a full inspection of the main turbine. At Nine Mile Point in upstate New York, workers replaced all four of the Unit 2 main power transformers, improving the station’s ability to maintain safe, reliable, carbon-free power for the upstate New York area.

“We carefully schedule these important upgrades, maintenance activities and technical inspections during periods of lower power demand to ensure our carbon-free nuclear units remain online 24/7 through the blistering summer months ahead,” said Tim Hanley, chief operating officer at Constellation.

About Constellation

Constellation is the nation’s largest producer of carbon-free energy and the leading competitive retail supplier of power and energy products and services for homes and businesses across the United States. Headquartered in Baltimore, its generation fleet powers more than 20 million homes and businesses and is helping to accelerate the nation’s transition to clean energy with more than 32,400 megawatts of capacity and annual output that is 90 percent carbon-free. Constellation has set a goal to eliminate 100 percent of its greenhouse gas emissions by leveraging innovative technology and enhancing its diverse mix of hydro, wind and solar resources paired with the nation’s largest carbon-free nuclear fleet. Constellation’s family of retail businesses serves approximately 2 million residential, public sector and business customers, including three-fourths of the Fortune 100. Learn more at or on Twitter at @ConstellationEG.


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