<P> Most nuclear fuels contain heavy fissile elements that are capable of nuclear fission , such as uranium - 235 or plutonium - 239 . When the unstable nuclei of these atoms are hit by a slow - moving neutron , they split , creating two daughter nuclei and two or three more neutrons . These neutrons then go on to split more nuclei . This creates a self - sustaining chain reaction that is controlled in a nuclear reactor , or uncontrolled in a nuclear weapon . </P>
<P> Most nuclear fuels contain heavy fissile elements that are capable of nuclear fission , such as uranium - 235 or plutonium - 239 . When the unstable nuclei of these atoms are hit by a slow - moving neutron , they split , creating two daughter nuclei and two or three more neutrons . These neutrons then go on to split more nuclei . This creates a self - sustaining chain reaction that is controlled in a nuclear reactor , or uncontrolled in a nuclear weapon . </P>
what is the fuel in a nuclear reactor
what is the fuel in a nuclear reactor
uranium - 235 or plutonium - 239
uranium - 235 or plutonium - 239