Explain the process of nuclear fission.

I would start by defining nuclear fission: 'Nuclear fission is the process of splitting up atoms and harnessing the energy from the reaction.' I would then proceed to explain how this occurs: 'Fission happens when a neutron is fired at high speed at a large nucleus, often Uranium or Plutonium. This extra addition of a neutron makes the nucleus highly unstable, and it splits into two smaller nuclei, plus a few extra neutrons. These extra neutrons go on to split more nuclei, starting a chain reaction of atom splitting. Each event of fission creates energy, and the energy from the reaction as a whole is harnessed.