A hospital worker handles radioactive sources used in medical procedures. Explain why irradiation and radioactive contamination are considered differently when assessing the risk to the hospital worker.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
A hospital worker handles two types of radioactive source: one is a sealed gamma-emitting source used to sterilise surgical equipment from outside its packaging, and the other is an unsealed liquid gamma-emitting tracer that is prepared and injected into patients.
Model answer (4 marks)
Irradiation occurs when the worker is exposed to a radioactive source that is outside the body or an object, so the worker does not become radioactive themselves.
Radioactive contamination occurs when radioactive atoms are introduced onto or into the worker, meaning the worker carries the source with them.
With contamination the worker is continuously exposed to radiation from the decaying atoms for as long as the source remains on or in them, making it harder to limit exposure.
With irradiation the worker can reduce risk by increasing distance from the source, reducing time of exposure, or using shielding, whereas these measures cannot remove contamination once it has occurred.
Radioactive contamination occurs when radioactive atoms are introduced onto or into the worker, meaning the worker carries the source with them.
With contamination the worker is continuously exposed to radiation from the decaying atoms for as long as the source remains on or in them, making it harder to limit exposure.
With irradiation the worker can reduce risk by increasing distance from the source, reducing time of exposure, or using shielding, whereas these measures cannot remove contamination once it has occurred.
Examiner tips
- Use the word ‘irradiation’ for external exposure and ‘contamination’ for internal or surface contamination. Show the difference in control measures – distance, time, shielding vs. removal of the source. Mention that contamination gives a continuous dose, making it harder to minimise.
Common mistakes
- Confusing irradiation with contamination. Failing to explain why contamination gives a continuous dose. Using vague terms like ‘radiation’ without specifying external vs. internal exposure.
Mark scheme (4 marks)
- Irradiation occurs when the worker is exposed to a radioactive source that is outside the body / object, so the worker does not become radioactive themselves.
- Radioactive contamination occurs when radioactive atoms are introduced onto or into the worker, meaning the worker carries the source with them.
- With contamination, the worker is continuously exposed to radiation from the decaying atoms for as long as the source remains on or in them, making it harder to limit exposure.
- With irradiation, the worker can reduce risk by increasing distance from the source, reducing time of exposure, or using shielding, whereas these measures cannot remove contamination once it has occurred.
Key terms in this question
irradiation · radioactive contamination
Related
- All Pearson Edexcel International GCSE Physics (4PH1) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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