Five Exelon Generation nuclear units in Illinois have returned to full-power operation after reducing their output late Thursday night and early Friday morning at the request of regional transmission operator PJM Interconnection, according to a company spokeswoman.
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The 912-MW Quad Cities-1 and 994-MW Quad Cities-2 in Cordova, Illinois, reduced output beginning at 11:40 pm CDT Thursday (0440 GMT Friday) "in coordination with PJM due to pricing signals and transmission line constraints," Exelon spokeswoman Dorothy Wallheimer said in an email Friday.
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Both units were operating at 100% of capacity as of 4:20 am CDT (920 GMT), Wallheimer said. Earlier that morning, unit 1 was operating at 93% and unit 2 at 94%, the US Nuclear Regulatory Commission said in its daily reactor status report.
The 1,268-MW Byron-1 in Byron, Illinois, reduced output for the same reason beginning at 11:55 pm CDT Thursday (0455 GMT Friday) and was operating at 100% as of 9:30 am CDT (1430 GMT) Friday, Wallheimer said. Earlier that morning, the unit was operating at 95% of capacity, NRC said in its report.
The 1,320-MW Braidwood-1 and the 1,295-MW Braidwood-2 in Braceville, Illinois, reduced output for the same reason beginning at 12:12 am CDT (0512 GMT) Friday, and both units were operating at 100% as of 8:30 am CDT (1330 GMT) that day, Wallheimer said. Earlier that morning, both units were operating at 98% of capacity, according to NRC's report.
Since 2015, Exelon has temporarily reduced off-peak output at one or more of its nuclear plants in Illinois numerous times in coordination with PJM because of grid constraints and what the company calls "pricing signals."
Exelon has previously said intermittent grid congestion has been occurring in the region around those plants because of transmission line outages for scheduled maintenance, large influxes of wind-generated power into the grid during off-peak hours, or a combination of those factors.
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