Dangers of Radiation (CIE IGCSE Physics)
Revision Note
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Dangers of Radioactivity
- Ionising radiation can damage human cells and tissues at high doses:
- This could be in terms of:
- Cell death
- Tissue damage
- Mutations
- Cancer
- As a result, its use needs to be kept to a minimum
- However, the benefits of using radiation in medicine can out way the potential risks
- The risks posed by the radiation are smaller than the risks associated with leaving the condition untreated
- For example, if a person has a cancerous tumour that is likely to kill them, then it is less of a risk to use radiotherapy than to leave the tumour
Tissue Damage
- Radiation is effectively used to destroy cancerous tumour cells
- However, it can cause damage to healthy tissue if it is not properly targeted
- This is mostly from high-energy radiation such as gamma rays and X-rays
Mutations
- If the atoms that make up a DNA strand are ionised then the DNA strand can be damaged
- If the DNA is damaged then the cell may die, or the DNA may be mutated when it reforms
- If a mutated cell is able to replicate itself then a tumour may form
- This is an example of cancer, which is a significant danger of radiation exposure
Diagram showing the damage caused to DNA by ionising radiation. Sometimes the cell is able to successfully repair the DNA, but incorrect repairs can cause a mutation
- Acute radiation exposure can have other serious symptoms:
- It can cause skin burns, similar to severe sunburn
- Radiation can reduce the amount of white blood cells in the body, making a person more susceptible to infections by lowering their immune system
- Because of this, it is very important to handle radioactive sources carefully
Safe Storage
- The risks associated with handling radioactive sources can be minimised by following a few simple procedures:
- Store the sources in lead-lined boxes and keep at a distance from people
- Minimise the amount of time you handle sources for and return them to their boxes as soon as you have finished using them
- During use, keep yourself (and other people) as far from the sources as feasible. When handling the sources do so at arm’s length, using a pair of tongs
Radioactivity warning sign
- When using tongs, gloves and safety specs are usually unnecessary when handling radioactive materials, unless there is a risk of the material leaking on to things
Disposing of Radioactive Waste
- If an isotope has a long half-life then a sample of it will decay slowly
- Although it may not emit a lot of radiation, it will remain radioactive for a very long time
- Sources with long half-life values present a risk of contamination for a much longer time
- Radioactive waste with a long half-life is buried underground to prevent it from being released into the environment
Radioactive waste with long half lifes are buried deep underground
Worked example
A student plans to use a gamma source to conduct an experiment. List four things that the student should do in order to minimise the risk to themselves when using the source.
Any four from:
- Keep the source in a lead lined container until the time it is needed
- Use tongs to move the source, rather than handling it directly
- The source should be kept at as far a distance from the student as possible during the experiment
- The time that the source is being used should be minimised
- After the experiment the student should wash their hands
- The date and the time that the radiation has been used for should be recorded
Safety Precautions
EXTENDED
- To mitigate the risks of radiation exposure, there are some safe practices that should be used:
- Radioactive sources should be kept in a shielded container when not in use, for example, a lead-lined box
- Radioactive materials should only be handled when wearing gloves, and with tongs to increase the distance from them
- It may be appropriate to wear protective clothing to prevent the body becoming contaminated
- The time that a radioactive source is being used for should be limited
Regulating Exposure
- Because of the harmful effects of radiation, it is important to regulate the exposure of humans to radiation
- The amount of radiation received by a person is called the dose and is measured in sieverts (Sv)
- One sievert is a very big dose of radiation
- It would cause acute radiation poisoning
- People would normally receive about 3 mSv (0.003 Sv) in one year
- To protect against over-exposure, the dose received by different activities is measured
- A dosemeter measures the amount of radiation in particular areas and is often worn my radiographers, or anyone working with radiation
A dosemeter, or radiation badge, can be worn by a person working with radiation in order to keep track of the amount of radiation they are receiving
Differences in Exposure
- The amount of radiation that a person receives is affected by a person’s occupation, lifestyle or location
- Some areas around the world have higher background radiation because they are closer to sources of radiation
- People that work with nuclear radiation receive more radiation
- The UK limit for nuclear industry employees is 20 mSv in one year
- The diagram below compares the dose received by some different activities
All living things emit a small amount of radiation: the amount of radiation within a banana is tiny, and not at all dangerous!
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