Reactor

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System used to initiate, maintain and control a fission chain reaction (chain reaction). The main part is a core with fissile nuclear fuel. In general, a reactor is equipped with a moderator, a shield and control devices. Reactors are built for research or power generation purposes. Reactors where the chain reaction is maintained by thermal neutrons (see 'neutrons, thermal') are called thermal reactors; if the chain reaction is maintained by fast neutrons, one refers to fast reactors. The first reactor was put into operation on 2nd December 1942 by a group of researchers headed by Enrico Fermi. (See 'pressurized water reactor', 'boiling water reactor').

Reactor structure, principle

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