Radioactive Contamination and Irradiation — AQA GCSE Physics
Contamination and irradiation are two different ways that radiation can be a hazard.
Irradiation
Irradiation is the process of exposing an object to nuclear radiation from a source. The irradiated object does not become radioactive itself.
Irradiation can be reduced by:
- shielding (e.g. lead),
- keeping a greater distance from the source, and
- limiting the time of exposure.
Contamination
Contamination occurs when radioactive atoms get onto or into an object. The contaminating atoms continue to decay and emit radiation, so the hazard remains until they are removed.
Comparing the hazards
- Inside the body, alpha sources are the most dangerous (highly ionising, energy absorbed by nearby tissue), so contamination is a serious concern.
- Outside the body, gamma (and beta) are more dangerous because they can penetrate the skin, whereas alpha is stopped by the outer layer of skin.
Working safely and peer review
Scientists use protective clothing, shielding, distance and limited exposure time. Findings on the effects of radiation are published and shared for peer review so that conclusions can be checked and trusted.
Exam tips
- Irradiation = exposure to radiation; the object does not become radioactive.
- Contamination = radioactive atoms on or in an object, which keeps emitting radiation.
- Reduce irradiation by shielding, distance and time.
- Inside the body alpha is most dangerous; outside, gamma.