FERC on Aug. 25 granted NextEra Energy’s request to waive certain rules under MISO’s tariff to allow the company to restart its Duane Arnold nuclear plant by the end of 2029.  

The commission ruled that NextEra is free to combine interconnection service and alter a point of interconnection, bringing the company a step closer to recommissioning the 50-year-old Duane Arnold Energy Center in Palo, Iowa (ER25-2989).  

NextEra is in the process of reinstating the plant’s operating license with the Nuclear Regulatory Commission and claims it could resume commercial operation on the plant by the end of 2028 at the earliest and the end of 2029 at the latest.  

In its Aug. 25 order, FERC permitted NextEra to combine leftover interconnection service at the site and use a nearby standalone interconnection agreement from a NextEra affiliate company to accommodate Duane Arnold’s historical peak winter net capacity range of 600-619 MW.  

The commission also allowed NextEra to use MISO’s generator replacement process to support recommissioning, even though an affiliate company — and not NextEra itself, the historical owner — is heading recommissioning efforts and cannot meet the original commercial operation deadlines of the stitched-together interconnection services.  

The Duane Arnold plant was idled in August 2020 after a derecho damaged the plant’s cooling towers and Alliant Energy ended its power purchase agreement five years ahead of schedule. NextEra subsidiaries quartered Duane Arnold’s interconnection service among four planned solar farms, only one of which was constructed and sold. The three remaining solar generator interconnection agreements are set to be bundled with NextEra affiliate Kinsella Energy Center’s 200-MW interconnection service to support the nuclear plant’s re-entry on the grid. NextEra plans to consolidate the interconnection service at the 161-kV level.  

NextEra said equipment necessary to repower the plant, including generator step-up transformers, isn’t scheduled to arrive until 2028, making the 2026 commercial operation target of the trio of original solar plans infeasible. The plant’s boiling water reactor is currently in long-term storage after being de-fueled. 

‘Old-fashioned Way’

In its order, FERC also accepted NextEra’s request for a Dec. 31, 2029, commercial operation deadline and agreed with the company that a late 2029 restart date would allow for “unexpected delays resulting from challenges driven by the complexity of a project of this nature including parallel supply chain activities, physical site work and regulatory processes that will be required to return the plant to power operations.”    

NextEra said it and MISO agreed that a change to the point of interconnection would have “no material adverse impacts” on the grid or other interconnection customers.  

NextEra said without waivers of MISO’s interconnection rules, it could have been forced to start fresh and apply to enter the RTO’s interconnection queue, which could add years to the restart goal.  

FERC said NextEra “acted in good faith in investing significant capital and securing interconnection rights in order to pursue a consolidated [generator interconnection agreement] necessary to recommission Duane Arnold.” NextEra said it could invest anywhere from $50 to $100 million over 2025 to fire up the plant within three to four years.  

The commission said without the waivers, MISO would have been forced to terminate the existing interconnection rights that Duane Arnold is counting on to reconnect. It said granting extra time would give NextEra the space to “obtain regulatory approvals, procure necessary equipment and recommission Duane Arnold.”  

Pamela Mackey Taylor, director of the Iowa Chapter of the Sierra Club, protested the waivers and said they weren’t necessary because they weren’t caused by unforeseen circumstances. Taylor argued also that the nuclear restart would lead to the abandonment of about 600 MW of solar development, making impacts more pronounced than NextEra claimed. Finally, she said NextEra has no guarantee from the NRC that Duane Arnold can reopen.  

NextEra said data centers’ need for high-capacity baseload generation led it to alter its solar power plans at the nuclear site.  

FERC said it wasn’t presented evidence that the solar projects will be “wholly abandoned.” The commission also said it would not opine on NextEra’s proceeding at the NRC. 

Speaking at Infocast’s 2025 Midcontinent Energy Summit on Aug. 19, MISO Senior Vice President Todd Hillman said nuclear power could play a bigger role in the RTO.  

“In MISO, we’re just doing it the old-fashioned way. We’re turning on old stuff,” Hillman joked, referencing nuclear power plant restarts at Palisades in Michigan and Duane Arnold in Iowa.