nuclear fusion and fission

• What is nuclear fission?

  It is the splitting of a large atomic nucleus into smaller nuclei.
• What is the process of nuclear fission?

  • A neutron is fired into a uranium nucleus.
  • The uranium nucleus splits into smaller nuclei and neutrons.
  • The released neutrons can hit other uranium nuclei, causing further fission.
• What is typically the nucleus that absorbs a neutron in a nuclear reactor?

  Uranium-235
• What happens when a uranium nucleus absorbs a neutron?

  It becomes uranium-236, which is violently unstable.
• What are the large fragments produced from nuclear fission called?

  Daughter nuclei
• What is a chain reaction in nuclear fission?

  It is when neutrons from one fission reaction cause further fission reactions.
• What percentage of energy from a fission reaction is carried by fast-moving neutrons?

  99%
• Why do fast-moving neutrons need to be slowed down in a nuclear reactor?

  To allow energy to pass on to other components in the reactor.
• What is the purpose of the coolant in a fission reactor?

  It is heated by the energy released from fission reactions to boil water and drive turbines.
• What are the main components of a fission reactor?

  • Nuclear fuel (uranium isotope)
  • Graphite core (slows down neutrons)
  • Control rods (regulate chain reaction)
  • Coolant (transfers heat to water)
  • Concrete shield (protects from radiation)
• What is the hazard associated with the daughter products of fission reactions?

  They are radioactive and can pose health risks.
• What is an uncontrolled fission reaction the basis of?

  An atomic bomb
• What is nuclear fusion?

  It is when two small, light nuclei join together to make one heavy nucleus.
• Where do fusion reactions primarily occur?

  In stars
• What happens when four hydrogen nuclei fuse together?

  They form one helium nucleus.
• What is the combined mass of four hydrogen nuclei?

  $6.693 \times 10^{-27} \text{ kg}$
• What is the mass of one helium nucleus?

  $6.645 \times 10^{-27} \text{ kg}$
• What is the missing mass when four hydrogen nuclei fuse into one helium nucleus?

  $0.048 \times 10^{-27} \text{ kg}$
• What happens to the missing mass in fusion reactions?

  It is converted to energy, which radiates away.
• What is a challenge of nuclear fusion?

  It requires the fusing of positively charged nuclei, which repel each other.
• How can particles travel quickly enough for fusion to occur?

  By being in a hot gas or plasma.