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
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
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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