Currently, there are 104 commercial nuclear reactors in the United States. In 2011, these plants provided 786 billion kilowatthours of electricity, or nearly one-fifth of total generation. The electrical output of the nuclear power plant fleet can be increased either by constructing new plants or by 'uprating' operating plants. Uprating generally involves physically modifying the plant to increase its generating capacity. Since 1977, more than 6,500 megawatts-electric (MWe) of nuclear uprates have been approved, and most of these have already been implemented. Through July 10, 2012, these cumulative uprates are roughly the equivalent of constructing six new nuclear power plants.
The Nuclear Regulatory Commission (NRC) reviews uprate requests from a nuclear utilities to assure the continued safe operation of these plants; uprates may not be implemented without NRC approval. Since the first requests in 1977, the NRC has approved 144 uprates. Uprates are categorized based on the magnitude of the increase in electrical output as well as the manner in which the increase is achieved. There are three types of uprates:
Uprates may be implemented incrementally or in combination with each other. The new capacity from nuclear uprates can be put into place quickly, as compared to new plant construction, and only as needed by actual demand growth. Although not restricted by NRC regulations, the total uprate potential of any reactor generally will not exceed 20% of the original licensed capacity of the reactor.
All but six of the 104 U.S. reactors have applied for an uprate, and only one reactor, Vermont Yankee (near Brattleboro, Vermont), applied and was approved for a full 20% extended uprate. Susquehanna Units 1 and 2 (near Berwick, Pennsylvania) and Edwin I. Hatch Units 1 and 2 (near Vidalia, Georgia) are the only reactors to have received NRC approval for all three types of uprates.
Currently, the NRC is reviewing applications for seven extended and nine measurement uncertainty recapture (MUR) uprates. If approved, these uprates would add about 1,140 MWe of nuclear capacity, in addition to the approximately 6,500 MWe already approved by the NRC. The total 7,640 MWe is roughly the equivalent of seven reactors the size of each of the Vogtle Units 3 and 4 reactors, which just received their combined construction and operation licenses in February 2012.
The map below shows the status of approved and pending uprates as well as the locations of nuclear power generators that have not yet submitted an application for an uprate.