6.8 - Nuclear Fission

• Nuclear fission is the splitting up of a large and unstable nucleus, into smaller nuclei.
• Spontaneous fission is when the fission is unforced and the atom splits by itself.

  Is spontaneous fission common or rare?

  Rare
• Fission can occur by an atom's nucleus absorbing a neutron and becoming even more unstable. The neutron helps to split the nucleus. 
• Steps for a nuclear fission chain reaction

  1. It starts with an unstable nucleus like uranium-235.
  2. A neutron is then fired at the unstable nucleus and causes it to split apart.
  3. The unstable nucleus splits into two 'daughter' nuclei and two or three neutrons, while also emitting lots of energy in the form of gamma radiation.
  4. The two or three neutrons that were released are then absorbed by other unstable nuclei and this repeats the process from step 3.
  5. This process then occurs over and over again in what we call a chain reaction.
• How nuclear power stations generate electricity

  1. Whenever unstable nuclei split apart they release lots of gamma radiation.
  2. This gamma radiation is then used to heat liquid water into steam.
  3. As the steam rises it turns turbines, and the kinetic energy of those turbine is converted into electricity by a generator. 
• Ensuring safety in nuclear reactors

  It is very important that the chain reaction of nuclear reactors is kept under control to avoid a nuclear meltdown. 

  To help keep the reaction stable, we can lower control rods into the nuclear reactor which absorb neutrons and slow down the chain reaction.
• What are the main pros of nuclear power?

  • Nuclear fuel such as uranium or plutonium is relatively cheap
  • Nuclear power plants can produce large and steady electric power
  • Nuclear power does not produce any greenhouse gas
• State and explain three cons of nuclear power.

  • They are very expensive to build.
  • The nuclear waste is radioactive so must be stored safely, but it's very expensive because it must be stored for a very long time in thick underground bunkers.
  • There is a risk of the nuclear chain reaction getting out of control and causing a nuclear meltdown.
• What is nuclear fission?

  Splitting of large unstable nuclei
• What happens during nuclear fission?

  It releases energy and smaller nuclei
• How many ways can nuclear fission occur?

  Two ways
• What are the two ways nuclear fission can occur?

  Spontaneously or by absorbing a neutron
• Is spontaneous fission common?

  No, it is rare
• What is required to start fission in nuclear reactors?

  Neutrons are needed to start fission
• What nucleus is commonly used in nuclear fission?

  Uranium-235
• What happens when a neutron is added to a nucleus?

  It makes the nucleus less stable
• What are the products of nuclear fission?

  Two smaller nuclei and energy
• What type of radiation is released during fission?

  Gamma radiation
• What is a chain reaction in nuclear fission?

  One fission triggers more fissions
• What can happen if a chain reaction is uncontrolled?

  It can release huge amounts of energy
• What is used to control the rate of fission in reactors?

  Control rods
• How do control rods work in a nuclear reactor?

  They absorb neutrons to slow the reaction
• What is the purpose of the energy released in nuclear fission?

  To heat water and produce steam
• What do steam turbines do in a nuclear power plant?

  They generate electricity
• What are the pros and cons of nuclear energy?

  Pros:

  • Cheap uranium or plutonium fuel
  • Large and steady energy production
  • Clean, no greenhouse gases

  
  

  Cons:

  • Expensive power plant construction
  • Costly nuclear waste disposal
  • Risk of major disasters
• Is nuclear energy considered renewable?

  No, it is not renewable
• Why is nuclear energy considered clean?

  It doesn't produce greenhouse gases
• What is a major risk associated with nuclear power plants?

  Malfunction leading to disasters
• Why do people feel suspicious about nuclear energy?

  Due to the risk of major disasters