GCSE Physics (AQA)

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Chain Reaction

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Atomic structure Nuclear fission and fusion

Chain Reaction

3:13 Nuclear Energy
Spec 4.4.4.1
Previous Energy from Nuclear Fission Next Nuclear Reactor
  • A nuclear fission reaction can cause further fission reactions, known as a chain reaction.
  • Each fission reaction releases two to three neutrons.
  • The larger nucleus splits into two smaller nuclei and neutrons during a fission reaction.
  • Neutrons can be absorbed by a large nucleus to cause new fission reactions.
  • Fission reactions start when a slow-moving nucleus is absorbed.
  • The process continues until all fissile nuclei have split and released neutrons.
  • A controlled chain reaction occurs if each fission causes only one further fission reaction.
  • To control the reaction, two neutrons must be absorbed by non-fissile nuclei, allowing only one successive reaction.
  • An uncontrolled reaction occurs if all released neutrons cause further fission reactions.
  • Uncontrolled reactions lead to rapid increases in the rate of chain reactions.
  • Uncontrolled chain reactions release huge amounts of energy, causing nuclear explosions.
  • Nuclear weapons work by facilitating uncontrolled nuclear reactions.
  • A nuclear explosion originates from a single nuclear reaction and releases unstable byproducts, leading to irradiation and contamination.

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