Contamination & Irradiation (Oxford AQA IGCSE Physics)

Revision Note

Contamination & Irradiation

Contamination

  • Contamination is defined as:

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

Irradiation

  • Irradiation is defined as:

The process of exposing a material to alpha, beta or gamma radiation

  • Irradiating a material does not make that material radioactive

    • However, it can kill living cells

Symbol warning of potential irradiation

Radiation hazard symbol in a yellow triangle, IGCSE & GCSE Physics revision notes
This sign is the international symbol indicating the presence of a radioactive material
  • 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 & 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

  • The hazard from contamination arises from the contaminating atoms decaying

    • The level of hazard this poses depends on the type of radiation the decaying atom emits

  • 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

Protecting against irradiation and contamination

  • It is important to reduce the risk of exposure to radiation

  • Radiation can mutate DNA in cells and cause cancer

  • Shielding is used to absorb radiation

    • Lead lined clothing is used to reduce irradiation for people working with radioactive materials

    • The lead absorbs most of the radiation that would otherwise hit the person

  • To prevent contamination an airtight suit is used by people working in an area where there may have been a radiation leak

    • This prevents radioactive atoms from getting inside the person

Protection from radiation

A lead apron and gloves are used to protect a user from irradiation and a radiation suit is used to protect  from contamination
Lead shielding is used when a person is getting an x-ray, as well as for people who work with radiation. Contamination carries much greater risks than irradiation

Comparison of Irradiation and Contamination Table

Irradiation

Contamination

Description

Object is exposed to radiation but does not become radioactive

Object becomes radioactive and emits radiation

Prevention

Prevented by using shielding, such as lead clothing

Prevented by safe handling of sources and airtight safety clothing

Causes

Caused by the presence of radioactive sources outside the body

Caused by inhalation or ingestion of radioactive sources

Examiner Tip

Irradiation and contamination are very commonly confused. Remember that something is radioactive only if it contains radioactive atoms. This can only occur from contamination, not from irradiation!

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