A research team is investigating the long-term storage of radioactive waste produced by nuclear power stations. Some of the waste contains isotopes with very long half-lives, whilst other waste contains isotopes with very short half-lives. Explain why both types of waste present a hazard, and describe the difference between the hazards posed by radioactive contamination and irradiation.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Nuclear power stations produce radioactive waste that must be carefully managed. The waste is classified partly according to the half-lives of the isotopes it contains.
Model answer (5 marks)
A long‑half‑life isotope remains weakly radioactive for a very long time, so it can continue to emit radiation for thousands of years and therefore poses a long‑term hazard. A short‑half‑life isotope is initially very radioactive, giving a large immediate dose, but it decays quickly, so the hazard is short‑lived.
Radioactive contamination is the unwanted presence of radioactive atoms on or in a material or object. The contamination is hazardous because the atoms continue to decay, emitting radiation, as long as they remain on the object.
Irradiation is exposure to nuclear radiation from an external source. The object does not become radioactive; the hazard only lasts while the object is near the source.
Radioactive contamination is the unwanted presence of radioactive atoms on or in a material or object. The contamination is hazardous because the atoms continue to decay, emitting radiation, as long as they remain on the object.
Irradiation is exposure to nuclear radiation from an external source. The object does not become radioactive; the hazard only lasts while the object is near the source.
Examiner tips
- Use the words "long‑term" and "short‑term" to link half‑life to hazard.
- Explain that contamination means the material itself becomes radioactive, whereas irradiation is only exposure.
- Mention that irradiation stops when the source is removed.
Common mistakes
- Confusing contamination with irradiation – saying the object becomes radioactive when it only receives radiation.
- Forgetting to mention the time scale of the hazard (long vs short).
- Using vague terms like "dangerous" instead of specifying radiation type or dose.
Mark scheme (5 marks)
- A long half-life isotope remains (weakly) radioactive for a long period of time, so presents a long-term hazard.
- A short half-life isotope is initially highly/very radioactive, posing a large immediate hazard.
- Radioactive contamination is the unwanted presence of radioactive atoms on or in a material/object.
- Contamination is hazardous because the radioactive atoms continue to decay (emitting radiation) over time whilst present on the object.
- Irradiation is exposure to nuclear radiation from an external source and only lasts whilst the object is near the source; the object does not become radioactive.
Key terms in this question
radioactive contamination · irradiation · isotope
Related
- All OCR A-Level Physics A (H556) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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