US power utility Exelon said on 19 July that the four nuclear plants serving Chicago and northern Illinois are approaching a combined 41 years, or 15,000 consecutive days, of continuous service at a time when the energy grid is increasingly challenged by extreme heat and storms. The Dresden, Byron, Braidwood and LaSalle NPPs located outside the Chicago region provide more than two-thirds of the state’s carbon-free energy and are the only clean-energy resources that can operate around-the-clock, 365 days a year.

Byron reached 5,000 consecutive days online last week, and Dresden reached 4,260 consecutive days during the same period. Braidwood Station has recorded 3,975 days and LaSalle Station 1,603 days, making the Illinois plants among those leading the industry for continuous operation.

Including Exelon Generation’s Clinton and Quad Cities nuclear stations, Illinois has six nuclear sites that provide 90% of the state’s clean energy and serve as an essential complement to the state’s other clean energy resources. The plants run close to 100% of the time in summer and winter when electricity use is high, while solar averages 20% and wind 30%, Exelon noted.

Low power prices and market rules that give fossil-fuel power plants an unfair advantage forced Exelon Generation to announce last year that it will close the Byron Generating Station in September and the Dresden Generating Station in November. The Braidwood and LaSalle nuclear plants also are at high risk of premature retirement in the near term.

With the first of the plants approaching permanent closure, policymakers continue to work on legislation that would preserve the plants as part of a comprehensive plan to maintain and grow clean-energy jobs, keep energy bills affordable and achieve net-zero emissions by 2050. The four Chicago-area plants support 28,000 direct and indirect jobs and contribute $3.5 billion annually to Illinois’ economy.

Losing Byron and Dresden will result in a cumulative increase in carbon dioxide emissions of more than 100 million metric tons over the next decade, even after taking into account the increase in renewables that would occur under the proposed energy legislation. This is more than the entire volume of carbon dioxide emissions otherwise projected for northern Illinois over the same period. These additional emissions would be caused by the regional grid operator dispatching fossil generation to make up for the lost zero-carbon energy coming from Dresden and Byron, Exelon explained.

Image: Unit 2 at the Byron nuclear power plant (photo credit: Exelon)