Currently (as of July 2012), 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: