Editing Control rod (section)

{{Short description|Device used to regulate the power of a nuclear reactor}}
[[File:PWR control rod assemby.jpg|thumb|Control rod assembly for a pressurized water reactor, above fuel element]]
'''Control rods''' are used in [[nuclear reactor]]s to control the rate of fission of the nuclear fuel – [[uranium]] or [[plutonium]].  Their compositions include [[chemical element]]s such as [[boron]], [[cadmium]], [[silver]], [[hafnium]], or [[indium]], that are capable of absorbing many [[neutron]]s without themselves decaying. These elements have different [[neutron capture]] [[neutron cross section|cross sections]] for neutrons of various [[neutron temperature|energies]]. [[Boiling water reactor]]s (BWR), [[pressurized water reactor]]s (PWR), and [[heavy-water reactor]]s (HWR) operate with [[thermal neutron]]s, while [[breeder reactor]]s operate with [[fast neutron]]s. Each reactor design can use different control rod materials based on the energy spectrum of its neutrons. Control rods have been used in nuclear aircraft engines like [[Project Pluto]] as a method of control.