The main use of nuclear energy is to generate electricity.  Originally it was seen as more convenient and probably cheaper than fossil fuel alternatives such as coal, gas and oil.  Nuclear energy has distinct environment advantages over fossil fuels, in that virtually all its wastes are contained and managed, that is, nuclear power stations do not cause any pollution.

Nuclear energy supplies some 14 per cent of the the world's electricity, more than the world used from all sources in 1960.  Today (2012) 30 countries use nuclear energy to generate up to three quarters of their electricity.  

While the World Nuclear Association website focuses on the use of nuclear energy to produce electricity, it is important to note that nuclear energy is also used to produce the radioisotopes used in many parts of our modern world, with health services, industry and even domestic safety very dependent on them.  Many homes have smoke detectors which depend on a tiny amount of americium, derived from plutonium made in a nuclear reactor.  In developed countries, about one half of all people will depend on nuclear medicine at some stage of their lives. 

Healey, Justin, edt. 2012, Nuclear energy debate, vol. 337, The Spinney Press, p. 1

However, nuclear power is one of the most controversial energies in use today.  The fear of accidents, and the problem of what to do with nuclear waste, are both major challenges for the industry.  An additional controversy is the association of nuclear materials with warfare and weapons.

Bowden, Rob, 2009, 'Nuclear energy', Energy sources, Franklin Watts, London, p. 17