March 14 (Reuters) - U.S. power company Exelon Corp, the nation's biggest nuclear operator, said modifications at its nuclear fleet, called uprates, could add more than 1,100 megawatts (MW) of carbon free energy by 2021.
This week, the U.S. Nuclear Regulatory Commission (NRC) accepted the company's application to increase the output at its Peach Bottom nuclear plant in Pennsylvania by 12.4 percent.
The two reactors at Peach Bottom currently have a capacity of 1,122 MW and the changes would add about 260 MW of capacity to the plant, Exelon said.
One megawatt can power about 1,000 U.S. homes.
The NRC said the standard review time for a so-called extended power uprate (EPU) application is 18 months after the agency formally accepts the application.
Exelon submitted the Peach Bottom application to the NRC in September 2012. The NRC staff initially determined the application was insufficient in certain respects and asked Exelon for additional information. The company has now provided that information.
Exelon over the past few years has sought to increase the output of several reactors by a much smaller 1.6 percent, including Byron, Braidwood, and LaSalle in Illinois and Limerick in Pennsylvania, according to the NRC website.
The NRC in 2012 said it put the review of the Byron and Braidwood on hold until Exelon provides more information.
In 2012, however, Exelon adjusted its uprate program - delaying a planned uprate at Limerick - primarily due weak market conditions, including weak natural gas and power prices and the continued sluggish economy.
Exelon said it had not yet determined the uprate percentage for Limerick but noted it would not exceed about 12 percent.
As of the end of 2012, Exelon said the program has delivered an additional 310 MW.
The company said about 75 percent of its planned output increases are either complete or are in the installation or design and engineering phases. The remaining 25 percent, if and when completed, would come from the uprate at Limerick currently scheduled to begin in 2017.
The company does not release projected costs on plant specific uprate projects.