AQA GCSE Physics

Revision Notes

4.3.2 Half-Life & Risk

Half-Life & Risk

  • The half-life is the time it takes for the activity of a radioactive source to decrease to half of its original value
  • Different radioactive isotopes can have very different half-lives
  • For example:
    • Francium-218 has a half-life of only 1 millisecond (0.001 seconds)
    • Polonium-210 has a half-life of about 140 days
    • Uranium-235 has a half-life of about 700 million years

Short Half-Life Values

  • If an isotope has a short half-life, the nuclei will decay very quickly
    • This means that the isotope will emit a lot of radiation in a short amount of time
  • If only a small amount of the isotope is used, having a short half-life can be advantageous, as the material will quickly lose its radioactivity
  • If a large amount is used, however, the levels of radiation emitted could make handling the isotope extremely dangerous

Long Half-Life Values

  • If an isotope has a long half-life then a sample of it will decay slowly
    • Although it may not emit a lot of radiation, it will remain radioactive for a very long time
  • Sources with long half-life values present a risk of contamination for a much longer time
  • Radioactive waste with a long half-life is buried underground to prevent it from being released into the environment

Radioactive waste, downloadable IGCSE & GCSE Physics revision notes

Depending on the activity of radioactive waste, it is buried in different ways

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