March 1 (Reuters) - About 24,400 megawatts (MW) of power capacity at U.S. nuclear power plants is expected to be offline at the peak of the 2013 spring refueling season, down more than 10 percent from a year earlier, data from a Reuters survey showed.
Last year, spring nuclear outages peaked at 27,500 MW of capacity in mid-April, according to the data.
The data assumes units currently on extended outages, such as the two reactors at Southern California Edison's (SCE) San Onofre plant in California and Omaha Public Power District's Fort Calhoun in Nebraska will still be shut.
The data also assumes that in addition to the 22,400 MW expected to be out for refueling outages on April 15 (the date of the usual spring peak), there will also be about 2,000 MW of nuclear capacity off for short-term, unexpected reasons. See
The 2,000 MW is the average amount of nuclear generation shut for unexpected, short-term reasons over the past five years.
Nuclear outages over the past five years have averaged about 23,200 MW in spring (2008-2012) and 21,500 MW in the autumn (2008-2012). See
Since 1999, the highest peak for spring outages was near 32,800 MW in 2011, and the highest peak for autumn was over 32,000 MW in 2012.
The 103 U.S. nuclear reactors are capable of generating almost 100,600 MW, enough to power about 80 million homes.
Nuclear reactors produce about 20 percent of the country's generation and operate around the clock as baseload facilities, providing some of the lowest-cost power.
Natural gas traders follow nuclear outages closely because plants burning gas usually make up much of the missing nuclear generation, especially in periods of high demand.
It takes roughly 200 million cubic feet of natural gas per day to generate about 1,000 MW.
The two reactors at SCE's 2,150-MW San Onofre plant shut in January 2012 after the discovery of premature tube wear in the steam generators. For the latest on San Onofre, see
SCE operates San Onofre for its owners, including SCE and Sempra Energy's San Diego Gas and Electric unit.
Omaha Public Power District said it hoped to restart the 478-MW Fort Calhoun in 2013. Fort Calhoun shut for refueling in April 2011 and has remained down due to damage caused by flooding of the Missouri River and needed safety upgrades since. For the latest on Fort Calhoun, see