Fewer outages and a lower amount of large curtailments worked to keep total U.S. nuclear plant availability in winter 2017-2018 higher than the winter 2016-2017 for the majority of the season.

Plant availability during the period spanning Dec. 1, 2017, to Feb. 28, 2018, peaked at 99.76% on Jan. 28 and notched its lowest point on Feb. 17 at 90.71%. In comparison, during the prior-year period spanning Dec. 1, 2016, to Feb. 28, 2017, total plant availability topped out at 97.12% on Jan. 21, 2017, and saw its low on Feb. 25, 2017, at 88.26%. Winter 2017-2018's levels were above winter 2016-2017's levels for 80 days, or 88.89% of the season, and this can be traced to fewer outages and large curtailments.
A total of 17 units were shut from Dec. 1, 2017, to Feb. 28, 2018, with 25 outages reported, including five reactors that were idled more than once. Entergy Corp.'s Grand Gulf 1 Mississippi was taken offline five times during the three-month period. In contrast, 25 units were idled from Dec. 1, 2016, to Feb. 28, 2017, with four units shut more than once over the time span.

At the independent system operator and regional transmission organization level, the Electric Reliability Council of Texas and the Midcontinent ISO saw nuclear generation reach its lowest points in December 2017, while ISO New England posted its low in January. The California ISO, New York ISO, PJM Interconnection and the Southwest Power Pool saw their nuclear power supply lows in February. The California ISO saw plant availability drop to close to 60% at 60.68% on Feb. 16 while production in the Midcontinent ISO stayed below the 100% level for the entire three-month period.
At the state level, Illinois, New York and North Carolina saw the most outages with two units taken offline in winter 2017-2018, while Alabama, Arizona, California, Georgia, Louisiana, Maryland, Massachusetts, Mississippi, Missouri, Tennessee and Virginia saw one unit shut over the period.
The 25 outages during the season were for a variety of reasons ranging from refueling and maintenance to reactor trips. Ameren Corp.'s Callaway plant in Missouri and Tennessee Valley Authority's Watts Bar 2 in Tennessee saw their refueling outages extend into winter 2017-2018 with Callaway returning to service on Dec. 18, 2017, and Watts Bar 2 restarted on Dec. 6, 2017.
Entergy's River Bend 1 in Louisiana saw the longest outage of the season with the unit taken offline from Jan. 8 until Jan. 30 for a 23-day refueling outage. Southern Co.'s Hatch 1 in Georgia was idled for 21 days for planned seasonal work and returned to service on Feb. 26. PG&E Corp.'s Diablo Canyon 2 in California is currently the longest ongoing refueling outage of the season with the unit still offline as of March 1 after being shut on Feb. 11.
Duke Energy Corp.'s McGuire 1 plant in North Carolina saw the shortest outage at one day, followed by TVA's Browns Ferry 3 in Alabama, Entergy's Grand Gulf 1 in Louisiana and Dominion Energy Inc.'s North Anna 2, which were each shut for two days.
Looking ahead, private sources indicate that 12 units may be taken offline for refueling outages this March while another 12 could be shut for planned seasonal work by April.
As of March 1, five units are offline.
For details of U.S. nuclear power plant operations, visit our Nuclear Availability and Status and Outage pages.
