Answer:
The elements that can be used to produce energy in a fission reactor are the elements that can sustain nuclear chain reaction. The elements should be fissile meaning that the nucleus of the material should be unstable and can undergo decay if bombarded with a neutron and subsequently releasing more neutrons that split other nuclei thus sustaining the chain reaction can be used as nuclear fuel. In general most element in the actinide series of the periodic table are fissile. The features of nuclear fuel are:
1) Have high probability of neutron capture.
2) Release more than 1 neutron on an average after it undergoes fission.
3) Have large half life.
4) Be available in nature in sufficient quantity.
The commonly used nuclear fuels are Uranium-235 and plutonium -239