Contamination & Irradiation (AQA GCSE Physics)
Revision Note
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
The Assassination of Alexander Litvinenko
Contamination is almost always a mistake or an accident
However, in 2006 a former Russian spy was poisoned by a radioactive isotope
His name was Alexander Litvinenko and he was contaminated with the isotope polonium-210
He died because of the poisoning
It is believed that the polonium-210 that poisoned Alexander Litvinenko was secretly put into a cup of tea he was drinking
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
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
Examiner Tips and Tricks
Students often find contamination and irradiation confusing because the language used to describe them is so similar. 'Describe the differences between contamination and radiation' is a really hard exam question if you are not secure in your understanding of each.
Contamination relates to the radioactive substance. If the radioactive substance gets somewhere that it's not supposed to be, that's contamination. It could get on your clothes, it could get inside your body, it could get into the soil where crops are subsequently grown; in all these instances, the presence of the radioactive substance is dangerous because when it decays and releases radiation, you will be exposed to that radiation in such a way that it can cause damage to your cells.
Irradiation relates to the radiation itself. If you stand close to a radioactive substance and you get in the path of the radiation, then you are being irradiated. If you build a house on an old nuclear waste site, you would live in the path of the radiation. If you blast a crate of medical supplies with gamma radiation, they are being irradiated. If you ingest a radioactive substance (contamination) then your cells are in the path of the radiation released in the decay and so your cells will be irradiated.
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