Nuclear Fission & Fusion

• What is the energy stored within the nucleus of an atom called?

  Nuclear potential energy
• What are the two types of nuclear reactions that can release energy from the nucleus?

  Fission and fusion
• How is nuclear fission defined?


  The splitting of a large, unstable nucleus into two smaller nuclei
• Which isotopes are commonly used as fuels in nuclear power stations?


  Isotopes of uranium and plutonium
• What happens during fission when a neutron collides with an unstable nucleus?


  The nucleus splits into two smaller nuclei and emits two or three neutrons
• What are the smaller nuclei produced during fission called?

  Daughter nuclei
• What type of radiation is emitted during nuclear fission?


  Gamma rays
• What type of energy do the products of fission possess?

  Kinetic energy
• What is spontaneous fission?


  Fission that occurs without additional energy being put into the nucleus
• What is induced fission?


  Fission that occurs when an unstable nucleus absorbs a neutron
• What is the half-life of uranium-235?


  700 million years
• Why is uranium-235 unsuitable for producing energy in a nuclear power station?


  It has a low activity and energy is released very slowly
• What happens to uranium-236 after it absorbs a neutron?

  It becomes very unstable and splits by nuclear fission almost immediately
• How many extra neutrons are required to induce a Uranium-235 nucleus to split by fission?


  Only one extra neutron
• What is a chain reaction in the context of nuclear fission?


  A process where neutrons released from one fission reaction induce further fission reactions
• What is the role of control rods in a nuclear reactor?


  They absorb neutrons to keep the number of free neutrons constant
• What can happen during uncontrolled chain reactions?


  They can become dangerous as the number of reactions increases rapidly
• How is a nuclear weapon related to uncontrolled chain reactions?


  It uses an uncontrolled chain reaction to release a huge amount of energy as an explosion
• How can the processes involved in nuclear fission be visually represented?


  • Through diagrams that illustrate the reaction
  • A neutron is fired into the target nucleus, causing it to split
• What is nuclear fusion?


  When two light nuclei join to form a heavier nucleus
• Why has nuclear fusion proven hard to reproduce on Earth?


  It requires extremely high temperatures to maintain
• Where does nuclear fusion take place naturally?


  In the centres of stars
• What happens to hydrogen nuclei during nuclear fusion in stars?


  They fuse into helium nuclei and release a large amount of energy
• What is the source of energy produced during nuclear fusion?


  A small amount of the particle’s mass is converted into energy
• What is the equation that describes mass-energy equivalence?


  E = mc2
• What do the variables in the equation E=mc2 represent?

  E is energy in Joules, m is mass in kilograms, and c is the speed of light in meters per second
• How much energy is released from 1 kg of hydrogen undergoing fusion?


  It is equivalent to the energy from burning about 10 million kilograms of coal