"The policy debate over the role of nuclear power in the nation's energy mix is rooted in the technology's fundamental characteristics. Nuclear reactors can produce potentially vast amounts of useful energy with relatively low consumption of natural resources and emissions of greenhouse gases and other pollutants. However, facilities that produce nuclear fuel for civilian power reactors can also produce materials for nuclear weapons. In addition, the process of nuclear fission (splitting of atomic nuclei) to generate power results in the production of radioactive material that must be contained and can remain hazardous for thousands of years. How to manage the weapons proliferation and safety risks of nuclear power, or whether the benefits of nuclear power are worth those risks, are issues that have long been debated in Congress. The 100 licensed nuclear power reactors at 61 sites in the United States generate about 20% of the nation's electricity. Four new reactors are currently under construction. About a dozen more are planned, but whether they move forward will depend largely on their economic competitiveness with natural gas and coal plants. Throughout the world, 438 reactors are currently in service or operable, and 65 more are under construction."
CRS Report for Congress, R42853
Federation of American Scientists: http://www.fas.org/sgp/crs/index.html