Daily U.S. nuclear capacity outages averaged 2.5 gigawatts (GW) during the summer of 2022 (June 1 through August 31), nearly 19% lower than the 3.1 GW average in the summer 2021. Summer nuclear capacity outages were lowest in mid-August, averaging 1.0 GW, and highest in June, averaging 3.8 GW.

Nuclear power plants undergo planned outages, usually for maintenance and refueling, and unplanned outages, which include weather-related disruptions and early retirements. U.S. nuclear outages are usually at their lowest in summer and winter because electricity demand is highest during these seasons and plant operators try to ensure plants are available to meet the increased electricity demand.

A planned nuclear generation outage is usually scheduled to coincide with a plant’s refueling cycle. U.S. nuclear power plants typically refuel every 18 to 24 months, mostly in fall and spring, when electricity demand is lower. During a refueling outage, plants typically optimize downtime by scheduling facility upgrades, repairs, and other maintenance work while the nuclear reactor is offline.

As of October 4, the average planned refueling outage in 2022 lasted 38 days, compared with an average of 30 days in 2021. The longer average refueling outage so far this year has mainly been due to two planned refueling outages that lasted longer than expected. The longest-lasting planned outages so far in 2022 have been at the Watts Bar and Fermi nuclear power plants.

Starting in March 2022, Watts Bar Unit 2 underwent a 121-day planned refueling outage, which also included a steam generator replacement project. The outage was originally planned to be completed in mid-May 2022; however, the outage lasted through June because of challenging weather conditions and technical issues.

Fermi Unit 2 conducted a 93-day refueling and maintenance outage from February to May 2022. The outage was delayed because the reactor automatically shut down before the scheduled beginning of the outage when a pump in the facility stopped working as expected.

Unplanned, or forced, nuclear generation outages can result from equipment failure, operational error, or external circumstances such as severe weather. As of October 4, 24 unplanned nuclear outages have occurred in 2022, compared with 51 in 2021.

We also classify early retirements as unplanned outages in the data. The early retirement of the Palisades Nuclear Plant in Michigan affected the amount of available nuclear capacity in the summer of 2022. The plant was retired in late May 2022, despite being licensed to operate through 2031, which was a loss of about 770 GW of nuclear-generating capacity.

Although Palisades was retired, it might reopen in the future. In September 2022, Michigan Governor Gretchen Whitmer sent a letter to the U.S. Department of Energy supporting an application for a federal grant to restart the Palisades facility. The letter is based on state concerns about CO2 emissions, electricity reliability, and the local economy.

Our Status of Nuclear Outages webpage, 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.