Edexcel IGCSE Physics 复习笔记 7.2.5 Dangers of Radiation

• Ionising radiation can damage human cells and tissues
• 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

   

• Because of this, it is important to handle radioactive sources carefully

Handling Radiation Safely

• 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!

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

Depending on the activity of radioactive waste, it is buried in different ways

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

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