U.S. summer nuclear outages declined in 2024, returning to 2022 levels

Average U.S. nuclear capacity outages during the summer of 2024 (June 1 through August 31) decreased to about 2.6 gigawatts (GW) per day from 3.1 GW in 2023, similar to average summer daily outages in 2022. Outages this past summer were highest in mid-July and early August, averaging 3.1 GW per day and peaking at 5.7 GW on the last day of August. More recently, nuclear outages have exceeded the five-year average because of weather-related disruptions and refueling outages.

Nuclear power plants experience both planned outages, usually for maintenance and refueling, and unplanned outages, which can be caused by technical issues, weather-related disruptions, and early retirements. Nuclear plant operators usually avoid scheduling planned nuclear outages during the summer and winter when electricity demand is highest and utilities need to have their reactors available to meet demand.

Unplanned, or forced, nuclear generation outages can result from equipment failure, operational error, or external circumstances such as severe weather. As of October 21, 39 unplanned U.S. nuclear outages occurred in 2024 compared with 55 in 2023.

Waterford Unit 3 in Louisiana had the longest unplanned outage at 59 days after two transformers caught fire on March 22. Peach Bottom Unit 2 in Pennsylvania, Cook Unit 2 in Indiana, and Calvert Cliffs Unit 2 in Maryland had the shortest outages at one day each. The two longest summer outages occurred at Oconee Unit 3 in South Carolina (16 days) and Watts Bar Unit 1 in Tennessee (11 days).

Hurricane Helene in late September caused power outages throughout the Southeast, where a significant number of nuclear plants are located, and affected operations at two nuclear plants:

• Operator Southern Nuclear took Unit 1 at the Hatch Nuclear Plant in Georgia offline, and Unit 2 was operating at 80% power due to decreased electricity load demand from storm damage to the distribution grid. The facility did not sustain significant physical damage.

• Operator Duke Energy decreased power at both units at Catawba Nuclear Station in North Carolina due to electrical equipment damage. Unit 2 returned to service after repairs, and Unit 1 entered its planned refueling and maintenance outage in early October.

Planned nuclear generation outages are usually scheduled to coincide with reactor refueling cycles in the spring and fall. As of July 31, U.S. nuclear plant refueling outages this year have lasted an average of 34 days compared with an average of 38 days in 2023. The outage at Sequoyah Unit 2 in Tennessee lasted the longest, 59 days, followed by Surry Unit 1 in Virginia at 58 days. Refueling outages at Fermi Unit 1 in Michigan and South Texas Project Unit 2 lasted 48 days.

In the second half of 2024, the U.S. nuclear fleet is expected to complete several refueling outages that began in September and October. Cooper Unit 1 in Nebraska, Arkansas Nuclear One, Comanche Peak Unit 2 in Texas, Byron Unit 2 and Braidwood Unit 1 in Illinois, Beaver Valley Unit 2 in Pennsylvania, and Catawba Unit 1 in South Carolina most recently began planned outages.

Our Status of Nuclear Outages web page, which is based on data collected by the U.S. Nuclear Regulatory Commission, provides daily operational information on each commercial U.S. nuclear power reactor.