it starts with an atom
An atom includes a nucleus, with protons and neutrons, and electrons orbiting around the outside. When a neutron is blasted at the nucleus, the nucleus can break apart releasing lots and lots of energy. This is called “fission.” When the nucleus breaks apart, its neutrons can also collide with other atoms setting off a chain reaction.
electricity is generated
The energy that is released from fission heats water that is used to turn the turbines of a generator to create electricity. There is no burning in this process. And, only a very small amount of uranium is needed: one pound of uranium has as much energy as three million pounds of coal.
burning coal releases carbon, a greenhouse gas
By contrast, in order for coal to heat water to turn the turbines of a generator to create electricity the coal must be burnt and that burning releases carbon into the atmosphere.
For more information on the benefits and costs of nuclear power, check out the debate: is it time to reconsider nuclear power?