Recall the differences between contamination and irradiation effects and…

The idea

Contamination means radioactive material gets onto or into an object, a surface or a person, so the source itself is transferred and keeps emitting inside or on the body. Irradiation means exposure to radiation passing through from a source that stays outside the body; the person does not become radioactive. A spilled dust that settles on skin contaminates it, whereas standing near a sealed source in a beam is irradiation. Hazards differ: contamination can be inhaled or swallowed and continue delivering dose until removed, and it can spread, so protective clothing, gloves, containment and careful disposal matter. Irradiation delivers dose only while exposure lasts, so distance, shielding and limiting time reduce it. Compare both by asking whether the source moves with the person and whether the hazard persists after leaving the area.

What earns the marks

• States that contamination transfers radioactive material onto or into an object or person, so the source is carried with them.
• States that irradiation is exposure to radiation from a source that remains outside the body, so the person does not become radioactive.
• Explains that contamination can be taken into the body by inhalation or ingestion and continues to deliver dose until removed.
• Explains that irradiation delivers dose only during exposure, so increasing distance, adding shielding or reducing time lowers the hazard.
• Compares the two hazards by noting that contamination can spread to other places and people whereas irradiation does not transfer the source.

Common mistakes and how to put them right

• Claims that an irradiated person becomes radioactive.

  Put it right by stating that irradiation leaves no radioactive material on the person.

• Treats contamination and irradiation as the same hazard.

  Put it right: Distinguish them by whether the radioactive material itself is transferred.

• Assumes a contaminated object stops being a hazard once removed from the source.

  Put it right: Note that the transferred material keeps emitting until it is removed or decays.

Exam tips

• Decide first whether the radioactive material itself moves to the person; if it does, the situation is contamination.
• Use the words 'source stays outside the body' when describing irradiation to keep the distinction sharp.
• When comparing hazards, mention both persistence of dose and spread to other people or surfaces.