U.S. nuclear capacity outages were 35% higher in summer 2020 than 2019

U.S. nuclear capacity outages averaged 4.2 gigawatts (GW) during the summer of 2020 (June through August), nearly 35% higher than the 2.7 GW average in summer 2019. Summer nuclear outages were at their lowest level from late June to mid-July, averaging 2.3 GW. Outages significantly increased in the latter half of July, peaking in late July at 6.5 GW and peaking again in August at 6.2 GW.

Nuclear outages are usually lowest in the United States during summer and winter because electricity demand is high during these seasons and plant operators need to meet the increased cooling and heating demand. Nuclear plants undergo planned outages, usually for maintenance and refueling, and unplanned outages, which include weather-related disruptions and early retirements.

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 during the 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.

So far in 2020, average planned outage times increased to 33 days, slightly longer than the 2019 average of 32 days. The increase was largely because of extended outages at two reactors: Fermi Unit 2 in Michigan and Grand Gulf in Mississippi. The Fermi Unit 2 refueling outage lasted 131 days because of COVID-19-related work delays. Grand Gulf underwent an 89-day extended refueling and maintenance outage while plant operators completed a modernization of its turbine control system.

Unplanned, or forced, nuclear generation outages can result from equipment failure, operational error, environmental conditions, or external circumstances such as severe weather.

Early retirements also factor into unplanned outages, which affected available summer capacity in 2020. Duane Arnold, a 601-megawatt (MW) capacity nuclear power plant in Iowa, experienced an unplanned outage in early August after high winds damaged the cooling towers. The facility was originally scheduled to retire on October 30, 2020, but operators chose to leave it closed given its close retirement date and estimated cost of repairs.

In April 2020, the Unit 2 reactor at the three-unit Indian Point nuclear power plant was retired, removing 998 MW of nuclear capacity. Although the reactor was licensed to operate through 2024, it was retired early because of increased operating costs and reduced revenues. Indian Point Unit 3 is scheduled to retire in April 2021, after which the Indian Point facility will be decommissioned.

EIA's Status of Nuclear Outages page, which is based on data collected by the U.S. Nuclear Regulatory Commission, provides daily operation information on each commercial U.S. nuclear power reactor.

Principal contributor: Slade Johnson