Explain why radioactive contamination is considered more hazardous than irradiation when a person is exposed to the same radioactive source.

AQA GCSE Physics (8463) — 4.4.3 Hazards and uses of radioactive emissions and of background radiation (Phys only) · Explain · 4 marks · View as Markdown

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

Model answer (4 marks)

Radioactive contamination occurs when radioactive atoms are deposited on or inside the body, or on other materials. These atoms remain in the body and continue to decay, emitting radiation for a long time. In contrast, irradiation only exposes the body to radiation while the source is present; once the source is removed the exposure stops. Therefore contamination causes greater and longer‑lasting damage and is harder to control or remove.

Examiner tips

  • Use the term ‘contamination’ to describe atoms on/inside the body. Explain that the atoms keep decaying. Contrast with irradiation where exposure stops when the source is removed. Show the causal link to greater damage.
  • Use clear, concise sentences and include the key terms: contamination, decay, prolonged exposure, irradiation, source removal.

Common mistakes

  • Confusing contamination with irradiation. Forgetting that contamination continues after the source is gone. Using vague language like ‘more dangerous’ without explaining why.

Mark scheme (4 marks)

  1. Contamination involves radioactive atoms being transferred onto or into the body / unwanted presence of radioactive atoms on other materials
  2. The contaminating atoms continue to decay / emit radiation from on or inside the body for a prolonged period of time
  3. Irradiation only exposes the object to radiation whilst the source is present / the exposure stops when the source is removed
  4. Therefore contamination causes greater / longer-lasting damage to the body / is more difficult to control or remove

Key terms in this question

radioactive contamination · irradiation

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