Explain the difference between radioactive contamination and irradiation, and state which presents the greater long-term hazard to a person.

AQA GCSE Physics (8463) — 4.4.2 Atoms and nuclear radiation · Explain · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Model answer (4 marks)

Irradiation is the exposure of an object to external nuclear radiation; the object itself does not become radioactive and the hazard stops when the source is removed.

Radioactive contamination is the unwanted presence of radioactive atoms on or inside a material; the radioactive atoms are transferred to the object.

Contamination presents the greater long-term hazard because the radioactive atoms remain on or in the object and continue to decay, emitting radiation over a long period of time.

Examiner tips

  • Use the exact terms ‘irradiation’ and ‘radioactive contamination’.
  • Explain that irradiation is external and stops with the source; contamination is internal and persists.
  • State clearly that contamination is the greater long‑term hazard.
  • Keep the answer concise – 4 points only.

Mark scheme (4 marks)

  1. Irradiation is the process of an object being exposed to nuclear radiation from an external source
  2. The irradiated object does not become radioactive / the hazard ends when the source is removed
  3. Radioactive contamination is the unwanted presence of radioactive atoms on or in a material / the radioactive atoms are transferred to the object
  4. Contamination presents the greater long-term hazard because the radioactive atoms remain on/in the object and continue to decay, emitting radiation over a long period of time

Key terms in this question

radioactive contamination · irradiation

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