Contamination
Contamination occurs if an object has a When unstable atoms give off particles that can be harmful to humans. material introduced into it. For example, an apple is:
- Process 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. if it is exposed to Energy carried by particles from a radioactive substance, or spreading out from a source. from cobalt-60, but
- A substance is contaminated if another substance is mixed or dispersed within it. if cobalt-60 is injected into it
As with irradiation, contamination can be very useful as well as being potentially harmful.
Medical contamination
Injected radioactive sources (such as technetium-99) can be used as A radioisotope used to trace, eg the flow of blood through an organ.. These substances make soft tissues, such as blood vessels or the kidneys, show up in medical imaging procedures.
An Atoms of an element with the same number of protons and electrons but different numbers of neutrons. emits The shortest wavelength and highest energy part of the EM spectrum. Produced by radioactive materials. that easily pass through the body. The rays reach a detector outside the body, for example an x-ray machine or a 鈥榞amma camera鈥. In this way, the radioactive isotope can be followed as it flows through the body. Changes in the amount of gamma Energy is 'given-out' by the material and the internal energy of the material will decrease. For example, infrared radiation from the Sun is emitted into space. from different parts would indicate how well the isotopes are flowing, or if there is a blockage.
In medical applications that involve injecting radioactive sources, efforts are made to ensure that contamination does not cause any long-term effects. This is done by choosing isotopes that:
- have very short The time it takes for the number of nuclei of a radioactive isotope in a sample to halve. Also defined as the time it takes for the count rate from a sample containing a radioactive isotope to fall to half its starting level.
- are not poisonous
In medical applications that involve using radioactive sources, efforts are made to ensure that irradiation does not cause any long-term effects. This is done by considering:
- the nature of the radioactive decay (A type of ionising radiation consisting of 2 protons and 2 neutrons., A type of ionising radiation consisting of a single electron. or A type of ionising radiation that is also part of the EM spectrum. It has no mass.)
- the half-life of the radioactive isotope
- the Poison level. of the substance and its radiation
The half-life should be long enough to produce useful measurements but short enough for the radioactive sources to decay to safe levels soon after use. If an isotope is chosen with a long half-life, the damaging effects of the radiation lasts too long and the dose received continues to rise.
The sources used typically have half-lives of hours. This means that after a few days there will be little radioactive material left in a person鈥檚 body.
Contamination to check for leaks
Tracers can be used to find leaks in water pipes. A gamma-emitting radioactive isotope is added to water in the pipe. Where there is a leak, contaminated water seeps into the ground, causing a build-up of gamma emissions in that area. The build-up of gamma emissions can be detected using a Device used to detect and measure the quantity of ionising radiation in an area.. This makes it easier to decide where to dig to find the leak.
The isotope used for this purpose must:
- be a gamma emitter, so it is easily detected
- have a half-life of several days, to allow the emissions to build up in the soil
- not be poisonous to humans because it will form part of the water supply
| Advantages of contamination | Disadvantages of contamination |
| Radioactive isotopes can be used as medical and industrial tracers | Radioactive isotopes may not go where they are wanted |
| Use of isotopes with a short half-life means exposure can be limited | It can be difficult to ensure that the contamination is fully removed so small amounts of radioisotope may still be left behind |
| Imaging processes can replace some invasive surgical procedures | Exposure to radioactive materials can potentially damage healthy cells |
| Advantages of contamination | Radioactive isotopes can be used as medical and industrial tracers |
|---|---|
| Disadvantages of contamination | Radioactive isotopes may not go where they are wanted |
| Advantages of contamination | Use of isotopes with a short half-life means exposure can be limited |
|---|---|
| Disadvantages of contamination | It can be difficult to ensure that the contamination is fully removed so small amounts of radioisotope may still be left behind |
| Advantages of contamination | Imaging processes can replace some invasive surgical procedures |
|---|---|
| Disadvantages of contamination | Exposure to radioactive materials can potentially damage healthy cells |
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 |
| Does not 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 | Once an object is contaminated, the radiation cannot be blocked |
| 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 | Does not 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 |
|---|---|
| Contamination | Once an object is contaminated, the radiation cannot be blocked |
| Irradiation | Stops as soon as the source is removed |
|---|---|
| Contamination | It can be very difficult to remove all of the contamination |