Contamination and irradiation
Irradiation
Shining visible radiationEnergy carried by particles from a radioactive substance, or spreading out from a source. from a torch beam onto a hand lights the hand up because the hand has been exposed to light.
Exposing objects to beams of radiation is called irradiationProcess of exposing an object to a source of radiation. Eg fruit exposed to gamma rays in order to destroy bacteria is said to have been irradiated.. The term applies to all types of radiation including radiation from the nucleiNuclei is the plural of nucleus. The nucleus is the central part of an atom. It contains protons and neutrons, and has most of the mass of the atom. of atomAll elements are made of atoms. An atom consists of a nucleus containing protons and neutrons, surrounded by electrons..
Irradiation from radioactive decayThe process in which unstable atomic nuclei break apart or change, releasing radiation as they do so. can damage living cells. This can be put to good use as well as being a hazard.
Radioactive beams can be used to preserve fruit by exposing the fruit to a radioactive source, typically Cobalt 60. The gamma rays emitted by the cobalt will destroy any bacteria on the fruit but will not alter the fruit in any significant way.
Irradiation does not cause radioactivity.
The method can also be used to sterilise surgical instruments.
Contamination
Contamination occurs if an object has a radioactiveWhen unstable atoms give off particles that can be harmful to humans. material introduced into (or onto) it. An apple exposed to the radiationEnergy carried by particles from a radioactive substance, or spreading out from a source. from cobalt-60 is irradiated but an apple with cobalt-60 injected into it is contaminatedA substance is contaminated if another substance is mixed or dispersed within it..
As with irradiationProcess of exposing an object to a source of radiation. Eg fruit exposed to gamma rays in order to destroy bacteria is said to have been irradiated., contamination can be very useful as well as being potentially harmful.
Doctors can deliberately contaminate a patient's body when it will help with diagnosis with a radioactive source, such as:
- drinking a radioactive mixture (barium meal) will make soft tissue such as your intestine show up on an x-ray
- technetium-99 is a radioactive isotope that can be introduced into the body to make soft tissue such as the brain or the thyroid show up on a scanner
Irradiation versus contamination
The two processes of irradiation and contamination are often confused. However they are very different and useful in their own right.
| Irradiation | Contamination |
| Occurs when an object is exposed to a source of radiation outside the object. | Occurs if the radioactive source is on or in the object. |
| Doesn't cause the object to become radioactive. | A contaminated object will be radioactive for as long as the source is on or in it. |
| Can be blocked with suitable shielding or moving away. | Once an object is contaminated, the radiation cannot be blocked from it. |
| Stops as soon as the source is removed. | It can be very difficult to remove all of the contamination. |
| Irradiation | Occurs when an object is exposed to a source of radiation outside the object. |
|---|---|
| Contamination | Occurs if the radioactive source is on or in the object. |
| Irradiation | Doesn't cause the object to become radioactive. |
|---|---|
| Contamination | A contaminated object will be radioactive for as long as the source is on or in it. |
| Irradiation | Can be blocked with suitable shielding or moving away. |
|---|---|
| Contamination | Once an object is contaminated, the radiation cannot be blocked from it. |
| Irradiation | Stops as soon as the source is removed. |
|---|---|
| Contamination | It can be very difficult to remove all of the contamination. |