Aims of this Episode:

  • Describe the process of Nuclear Fission;
  • Describe the function of different components of a Nuclear Reactor;
  • Explain the difference between Nuclear Fission and Nuclear Fusion.

Nuclear Fission

Nuclear Fission is currently the only way that humans can generate electricity from a nuclear reaction. It is the splitting of a heavy nuclei [middle of an atom, not including the electrons] caused by absorbing a neutron.

The heavy nuclei is either Uranium or Plutonium, since they are already pretty unstable. When they split, a large amount of energy is given off (in a thermal form), along with two waste nuclei (highly radioactive) and three more neutrons. These neutrons then go on to complete more fission reactions (a chain reaction)… and so on.

In a Nuclear Power Station there are a number of components that you need to be familiar with:

Fuel Rods – These contain the Uranium or Plutonium fuel and so this is where the reactions occur.

Control Rods – As their name suggests these control the reaction by absorbing some of the neutrons created during a fission reaction. If we just let each reaction create three more then the process would get out of control, so we absorb some of the neutrons to maintain the reaction at a desired level. To increase the reaction, the control rods are removed and to reduce the reaction they are inserted further into the Reactor.

Moderator – This is a solid or liquid that is used the slow the neutrons down. If the neutrons (created during each reaction) were not slowed down then they would be too fast to successfully cause more reactions, so the Chain Reaction would stop.

Nuclear Fusion

Nuclear Fusion is the fusing of two nuclei to produce energy.

At present the only places that Nuclear Fusion successfully produces energy are in stars like the Sun. This process uses lighter elements such as Hydrogen. The Hydrogen nuclei fuse together to produce Helium nuclei and a lot of energy. The waste products of this reaction are not as dangerous as those of Nuclear Fission.

To find out more about Nuclear Fission and Fusion, watch this video.


The Chernobyl disaster occurred when a reactor in a Nuclear Fission Power Station overheated. This led to an explosion and fire that spread radioactive waste across Europe.

Once you’ve got your head around the different parts of a Fission Power Station (above) check out this video.

PS: We don’t think Dr Chekov (mentioned in the podcast) actually existed and the dramatisation is meant as a scientific explanation, not a re-enactment of history (basically we made the events up, if you hadn’t already guessed).

S@S 019: Nuclear Fission and Fusion
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