There are two types of nuclear power: fusion and fission. Nuclear fusion is the method of power generation which happens on the sun. If we could harness this, we would be able to produce huge amounts of power.
Nuclear fission is what we use in nuclear power stations. It works by smashing a neutron into a uranium nucleus – the middle of the atom. This then splits into smaller nuclei, and some more neutrons are thrown out. These neutrons all then hit more uranium nuclei, which split apart, release more neutrons, etc. From this chain reaction, energy is produced, which is harnessed; hence the nuclear power station is born.
The problem with this sort of power generation is that it creates toxic waste. It also needs to be under surveillance 24 hours a day, seven days a week, as if something goes wrong, the effects could be devastating.
Nuclear fusion works in a very different way. It occurs by fusing (hence the name) two atomic nuclei, to make a larger nucleus. This produces massive more amounts of energy than fission. Our sun and other stars use this process, however we cannot currently control it, meaning it is not a useful power source.
Because of the way it works, nuclear fusion is a much cleaner method of power generation. It produces less toxic waste, which decays faster than nuclear fission waste does. In the grand scheme of things, you could even argue that it is more clean than using coal, oil or gas – the dirty fossil fuels.
It seemed impossible not so long ago, for the idea of nuclear fusion power stations, as it seemed to be impossible to ever control. However, some recent breakthroughs in technology mean that some scientists are predicting that we may have some nuclear fusion power plants by as early as 2020. That is just a very rough prediction, providing the correct technology advances.