How Nuclear Power Works

Summary

In simple terms, a radioactive material such as uranium spontaneously breaks apart. As it does so, it gives out energy and this energy, in the form of heat, can be used to drive an electricity generator. (Other forms of fuel such as coal, oil and gas also use heat to drive a generator, although they are burned rather than use radioactivity.) Although far less uranium is needed to supply a power station than fossil fuels, the process still consumes material and the uranium eventually has to be replaced.

The uranium releases its heat to a primary coolant, usually water, and this is then transferred to a secondary coolant which drives the turbines to produce electricity. Because the two coolants are kept apart, the radioactivity is contained within a substantial shield.

In detail

Radioactivity is the spontaneous disintegration of the atomic nucleus of a material, giving out subatomic particles or electromagnetic rays. The energy that occurs when this happens can be used to provide heat which, in turn, can drive a generator to produce electricity. There are many radioactive elements but the one which is used in all existing power nuclear stations is uranium.

One reason why uranium is used in nuclear power is that it has the advantage of being 'fissile' - that means that some of the particles that are emitted by radioactivity hit other atoms which force them to release particles in turn. A chain reaction is thus created.

Uranium does not occur naturally but has to be retrieved from an ore such as pitchblende or carnotite. Pure uranium consists of the isotope* uranium-238 (U238) which makes up over 99%, 0.7% of uranium-235 and a trace of uranium-234. Because U238 is non-fissile, the natural uranium has to be enhanced or enriched to provide enough of the fissile U235 to be useable as a fuel.

*isotope: a form of an element which has a varying number of neutrons in its atoms. They are identified by a number which is the sum of their protons and neutrons. Isotopes of an element are essentially the same but vary in some characteristic/s.

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