Edexcel IGCSE Physics: Double Science 复习笔记:7.2.5 Dangers of Radiation

Edexcel IGCSE Physics: Double Science 复习笔记:7.2.5 Dangers of Radiation

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

 

 

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

转载自savemyexams

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