Nuclear power

... explains how nuclear power reactors use a controlled fission reaction to produce power.


Nuclear reactors have been producing electricity since the 1950s and, in early 2003, there were 441 nuclear reactors operating in 30 countries with a total installed capacity of 359 GW.

Nuclear reactors

Nuclear reactors depend on a reaction between neutrons and the atomic nuclei of the fuel for their operation. Uranium, the fuel for almost all reactors, consists principally of two isotopes, uranium-235 and uranium-238.

In natural uranium, the fuel for early reactors, those isotopes are in the proportion of 0.7 per cent and 99.3 per cent, respectively, by weight.
The enriched uranium used in most currently operating reactors contains
about 2.5 per cent of uranium-235.

Energy is released when a uranium-235 nucleus absorbs a neutron and undergoes fission, that is, it splits into two large energetic fragments or fission products, accompanied by the release of several high energy or fast neutrons and some gamma radiation.

The neutrons are slowed in the reactor so that they induce further fissions in the uranium-235. Such neutrons are often called thermal neutrons and the reactors that rely upon them thermal reactors.

 

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