Nuclear energy is energy that is released from an atomic nucleus. It is harnessed by controlling nuclear reactions which release energy that generate electricity, propulsion, and heat. Nuclear energy is released from atoms in two ways: nuclear fusion and nuclear fission. Nuclear fission and radioactive decay are the two most common methods of utilizing nuclear energy to do significant work. In nuclear fission, atoms are split apart to form smaller atoms, releasing energy.
Nuclear power plants use nuclear fission to produce electricity. The fuel that most nuclear plants use is uranium, a nonrenewable fuel. U-235 is a certain kind of uranium whose atoms are easily split. Nuclear power provides 7% of the world's energy and 17% of the world's electricity. In 2005, there were a total of 66 nuclear power plants(composed of 104 licensed nuclear reactors) throughout the United States.
Nuclear power has by-product wastes in the form of heat and radioactive waste. Nuclear generated electricity is touted as a great alternative because it does not emit carbon dioxide into the environment. In the U.S. alone, nuclear energy prevents the emissions of about 697 million metric tons of carbon dioxide. This is about as much carbon dioxide as is released from all American passenger cars combined.
Nuclear energy has a cloudy future because of the war waging over it. Opponents say that because of the problems with long term storage of nuclear waste, radioactive contamination, and military uses for war, nuclear energy is not a safe alternative. Proponents say that because of its good track record, this type of energy is controllable, and perfectly safe when used within guidelines. They also argue that it is a renewable energy source and has very little effects on the environment.