Nuclear fission and fusion

• What is Nuclear fission

  The splitting of large unstable nuclei to form smaller more stable nuclei
• Give an example of a fissionable isotope

  Uranium- 235
• What needs to happen to induce fission

  • The unstable nuclei must absorb a neutron
  • spontaneous fission( where no neutron absorption occurs) is rare
• Alongside two smaller nuclei what else is emitted in a fission reaction

  • Two or three neutrons
  • gamma rays
  • energy
• What form of energy do all fission products have

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

  • An unstable nucleus absorbs a neutron
  • the nucleus undergoes fission and releases 2 or 3 further neutrons
  • these induce more fission which results in a chain reaction
• Whats the 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
• What are the three main components of the core a nuclear reactor

  • Fuel rods
  • control rods
  • Moderator
• What’s the 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 is the chain reaction in a fission reactor kept under control

  • Control rods are positioned in between the fuel rods
  • the rate of fission is controlled by moving these rods up and down
  • the lower the rods are inserted the slower the rate of fission
• What term is used to describe the nuclei in which fission can be induced through the absorption of slow neutrons

  Fissile nuclei
• What is nuclear fusion

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

  Deuterium and Tritium
• Which releases more energy nuclear fission or nuclear fusion

  Nuclear fusion
• Explain the 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
• Explain why nuclear fusion is currently not a viable way to produce energy on earth

  With current equipment / techniques the energy required is greater than the energy produced resulting in a net energy loss