7.2.6Acids, Bases and Salts
Contamination and Irradiation — Cambridge IGCSE Chemistry 0620 Revision Notes & Topical Questions
5 min read 4 parts Lesson 7 of 11 Unit quiz
Section 1 of 4Key Definitions
Contamination
- The unwanted presence of materials containing radioactive atoms on another material, or inside a living body.
Irradiation
- Exposing a material or person to alpha, beta or gamma radiation, which does not make the material radioactive.
Radioactive
- Something is radioactive only if it contains radioactive atoms that are emitting radiation.
Sterilisation
- Irradiating surgical equipment or food with radiation to kill micro-organisms, so they last longer or are safe to use.
Section 2 of 4Hazards and Control
Hazards and Control
Irradiation hazard
- Radiation from outside the body can damage living cells, so exposure should be limited.
Contamination hazard
- Atoms that are decaying inside or on the body keep emitting radiation for as long as they remain there.
Shielding
- Lead absorbs most of the radiation, and is used to reduce irradiation of people working with sources.
Containment
- Airtight suits and careful handling prevent radioactive atoms from getting onto or into a person.
| Feature | Irradiation | Contamination |
|---|---|---|
| Object becomes radioactive? | No | Yes |
| Typical cause | Exposure to an external source | Leak, inhalation or ingestion of a source |
| Main protection | Shielding such as lead | Airtight suits and safe handling |
| Level of risk | Lower | Much higher, due to continuous exposure |
Section 3 of 4Protection Steps
1
Limit the time spent close to a source, because the total dose received depends on how long exposure lasts.
2
Increase the distance from a source, since the dose received falls rapidly as distance increases.
3
Place shielding such as lead between the person and the source during handling or imaging.
4
Use airtight containment and monitoring so that radioactive atoms cannot enter the body or spread.
Section 4 of 4Exam Checklist & Tips
7.2.6 – Key Points for the Exam
- Contamination Unwanted radioactive atoms present on or inside another material or body.
- Irradiation Exposing a material or person to radiation without making it radioactive.
- Shielding Using a dense material, such as lead, to absorb radiation.
- Sterilisation Killing micro-organisms by irradiating a material.
- Airtight suit Protective clothing that stops radioactive atoms from reaching the wearer.
Common Mistakes
- Saying that an irradiated object becomes radioactive; irradiation does not make an object radioactive.
- Confusing contamination with irradiation, when they are different hazards with different protections.
- Saying lead shielding protects against contamination;
- shielding stops external radiation but does not stop atoms already inside the body.
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