Hazards of Contamination & Irradiation (OCR Gateway GCSE Physics)

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Hazards of Contamination & Irradiation

Half-Life and the Hazards from Radioactive Material

  • 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
    • It is therefore commonly use in medical tracers
  • If a large amount is used, however, the levels of radiation emitted could make handling the isotope extremely dangerous
    • This is because the isotope will have a large activity
    • The person will be exposed to a lot of radiation in a short period of time

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

Worked example

Summarise the difference in the risk posed by radioactive sources with very short and very long half-lives with regards to:

(a) Irradiation

(b) Contamination

Part (a)

    • A short half-life means a source has a high activity
    • This means there is a high rate of radioactive emissions, compared to a source with a long half-life

Part (b)

    • Sources with long half-lives will remain radioactive for longer
    • They need to be controlled for longer, to prevent them spreading
    • Shielding and storage may be required

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Joanna

Author: Joanna

Joanna obtained her undergraduate degree in Natural Sciences from Cambridge University and completed her MSc in Education at Loughborough University. After a decade of teaching and leading the physics department in a high-performing academic school, Joanna now mentors new teachers and is currently studying part-time for her PhD at Leicester University. Her passions are helping students and learning about cool physics, so creating brilliant resources to help with exam preparation is her dream job!