Answer:
In 2008, the "average" nuclear power plant generated about 12.4 billion kilowatt-hours (kWh). There were 65 nuclear power plants with 104 operating nuclear reactors that generated a total of 808.97 billion kilowatt-hours (kWh), or almost 20% of the nation's electricity.
Thirty-six of those plants had two or more reactors. The smallest nuclear plant has a single reactor with 476 MW of generation capacity and the largest has three reactors with a total of 3,825 MW of capacity.
Source: US Department of Energy