(Reuters) - About 20,874 megawatts of nuclear power capacity is expected to be out of service in the United States in the upcoming autumn refueling season, according to Reuters data On Thursday.
That is roughly 4.9 percent, or 974 MW, above the 19,900 MW of nuclear capacity that was shut last year during mid-October, the height of the autumn refueling season, the data showed.
The data assumes units currently on extended outages -- like the San Onofre reactors in California and the Crystal River reactor in Florida -- will still be shut in mid-October.
Southern California Edison, the unit of California power company Edison International that operates San Onofre, said Unit 3 will not refuel as scheduled in October.
Due to the damage in Unit 3's steam generators, fuel will be removed from the reactor for the foreseeable future, SCE said in a filing.
"The current plan for Unit 3 is to de-fuel the reactor and place appropriate systems in a layup condition while analysis and testing continue given the uncertain timing of the likely repairs and restart," the company said.
A spokeswoman said a schedule to remove the fuel had not been determined. Nuclear fuel in Unit 2 was removed earlier this year. Unit 2 shut in January for refueling and inspections which revealed damage to its steam generators.
Neither San Onofre unit can return to service without the approval of the Nuclear Regulatory Commission. SCE is planning to cut staff at the plant before the end of the year.
The Fort Calhoun station which had been seen trying to restart in September, will now remain shut at least a few more months, the Omaha Public Power District said.
Nuclear outages over the past five years have averaged about 20,400 MW in autumn (2007-2011) and 23,000 MW in spring (2008-2012).
Since 1999, autumn outages peaked near 27,200 MW in 2009 and bottomed at about 12,300 MW in 2004. Spring outages have peaked at 32,800 MW in 2011 and bottomed at 16,100 MW in 2004.
The 104 U.S. nuclear power reactors are capable of generating almost 101,200 MW of electricity, enough to power about 80 million homes.
Nuclear reactors operate around the clock as baseload facilities, providing some of the lowest-cost power.
Natural gas traders follow the nuclear outages closely because plants burning gas usually make up much of the missing nuclear generation, especially during periods of high demand.
It takes about 200 million cubic feet of natural gas per day to generate about 1,000 MW of electricity. One billion cubic feet of gas could generate about 5,000 MW of electricity.
(Reporting by Naveen Arul and Koustav Samanta in Bangalore and Eileen O'Grady in Houston; Editing by Marguerita Choy)