Radioactive contamination is the unwanted presence of materials containing radioactive atoms on other materials.

• A substance is only radioactive if it contains radioactive atoms that emit radiation

• Contamination occurs when a radioactive isotope gets onto a material where it should not be

  • This is often due to a radiation leak

• As a result of this, the small amounts of the isotope in the contaminated areas will emit radiation and the material becomes radioactive

The hazard from contamination is due to the decay of the contaminating atoms. The type of radiation emitted affects the level of hazard.

Irradiation is the process of exposing an object to nuclear radiation. The irradiated object does not become radioactive. However, it can kill living cells.

Irradiation can be used as a method of sterilisation:

• Surgical equipment is irradiated before being used in order to kill any micro-organisms on it before surgery

• Food can be irradiated to kill any micro-organisms within it

• This makes the food last longer without going mouldy

Hazards of Irradiation and Contamination

• Although irradiation can cause harm, contamination has the potential to cause far more harm, due to the continuous exposure to radiation that it will produce

• Contamination is particularly dangerous if a radioactive source gets into the human body

  • The internal organs will be irradiated as the source emits radiation as it moves through the body

Question: Summarise the difference in the risk posed by radioactive sources with very short and very long half-lives with regards to:

(a) Irradiation.

(b) Contamination.

(a) Sources with short half-lives present a greater risk of irradiation

• A short half-life means a source has a high activity

  1. This means there is a high rate of radioactive emissions, compared to a source with a long half-life

(b) Sources with long half-lives present a greater risk of contamination

• Sources with long half-lives will remain radioactive for longer

  1. They need to be controlled for longer, to prevent them spreading

  2. Shielding and storage may be required