Topic 9 - Nuclear Decay and Nuclear Energy

• What is nuclear fission?

  The splitting of large, unstable nuclei to form smaller more stable nuclei (+ the emission of spare neutrons).
• What usually needs to happen to induce fission?

  • The unstable nuclei must absorb a neutron.
  • Spontaneous fission (where no neutron absorption occurs) is rare.
• What term is used to describe nuclei in which fission can be induced through the absorption of slow neutrons?

  Fissile Nuclei
• 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.
• Name a common fissile nuclei.

  Uranium-235
• What are the three main components of the core a nuclear reactor?

  1. Fuel rods
  2. Control rods
  3. Moderator
• 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.
• What is 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.
• 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 is 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.
• What is nuclear fusion?

  The joining of two light nuclei to produce a heavier nucleus 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.
• What must the casing of a fission reactor do?

  Absorb any neutrons and gamma radiation that is released in the fission reactions, to prevent it from passing through to outside the reactor.
• Why are fission products particularly dangerous?

  They have very long half-lives meaning they remain radioactive for a very long time.
• What is the nuclear symbol for a neutron?