General

• Nuclear fission


  The splitting of large, unstable nuclei to form smaller more stable nuclei (+the emission of spare neutrons)
• Fissionable isotope

  • Uranium - 235
• What usually needs to happen to induce fission

  1. The unstable nuclei must absorb a neutron

  2. Spontaneous fission (where no neutron absorption occurs) is rare
• What is emitted in a fission reaction

  • Two or three neutrons
  • Gamma rays
  • Energy
• Fission products

  Kinetic energy
• What takes place during a chain reaction in a nuclear reactor

  1. An unstable nucleus absorbs a neutron

  2. The nucleus undergoes fission and releases 2 or 3 further neutrons

  3. These induce more fission, which results in a chain reaction
• Consequence of an uncontrolled chain reaction


  • The rate of fission events becomes to high and results in the production of too much energy
  • This can lead to a nuclear explosion
• Main components of the core a nuclear reactor

  • Fuel rods
  • Control rods
  • Moderator
• Role of the moderator in a nuclear reactor

  To slow down the neutrons so they are travelling at speeds which allow them to be absorbed by fissile nuclei and cause fission
• How the chain reaction in a fission reactor is kept under control

  1. Control rods are positioned in between the fuel rods

  2. The rate of fission is controlled by moving these rods up and down

  3. The lower the rods are inserted, the slower the rate of fission
• Fissile nuclei


  Nuclei in which fission can be induced through the absorption of slow neutrons
• Nuclear fusion

  The joining of two light nuclei to produce a heavier nuclei and release energy
• Isotopes of hydrogen commonly used in nuclear fusion

  • Deuterium and Tritium
• Nuclear fusion releases more energy than nuclear fission
• Difficulty of generating energy through nuclear fusion

  • Fusion requires very high temperatures which in itself requires large quantities of energy and also requires casing which can withstand them
• Nuclear fusion is currently not a viable way to produce energy on Earth