AQA A Level Physics

Revision Notes

8.1.6 Radiation Safety

Safe Handling of Radioactive Sources

  • It is very well known that radioactive sources are dangerous if handled improperly
  • When choosing a source to work with, the following characteristics are preferred:
    • Short-lived isotopes are preferred to long-lived ones
    • The smaller the amount of radioactive material, the better
  • The risk associated with radioactive materials depends on the amount and type of radiation
    • For example, alpha radiation is more ionising than gamma radiation but does not penetrate as far
  • The biggest risks when working with radioactive sources are exposure and contamination
    • Contamination happens when a piece of radioactive material is transferred onto a person, or a personal item, where it can then decay and cause damage
  • The radiation hazard warning safety symbol is used to warn about hazardous materials, locations or objects

Radiation-Hazard, IGCSE & GCSE Physics revision notes

  • Precautions must be taken to reduce the risk of harm when using radioactive sources. These include:
    • Keeping radioactive sources shielded when not in use, for example in a lead-lined box
    • Wearing protective clothing to prevent the body from becoming contaminated
    • Keeping personal items outside of the room to prevent these from becoming contaminated
    • Limiting exposure time so less time is spent with radioactive materials
    • Handling radioactive materials with long tongs to increase the distance from them
    • Monitoring the exposure of workers, such as radiographers, using detector badges

radiation-badge, IGCSE & GCSE Physics revision notes

A badge containing photographic film can be used to monitor a person’s exposure to radiation

Radiation in Medicine

  • Radioactive materials can cause a huge amount of damage to the human body, however, under careful management, they can be of huge benefit in medicine

Radiation Therapy

  • Gamma radiation can be used to destroy cancerous tumours
    • The gamma rays are concentrated on the tumour to protect the surrounding tissue
  • Less penetrating beta radiation can be used to treat skin cancer by direct application to the affected area

 

  • Precautions for the patient:
    • The patient should be protected with lead to cover parts of the body not to be exposed to radiation
    • The exact dose should be calculated carefully
    • The dose should be directed very accurately at the cancerous tissue to minimise damage to healthy tissue
  • Precautions for the radiographer:
    • The radiographer should handle the source remotely with tongs or a machine
    • The radiographer should be protected by a screen
    • The radiographer should be a long way from the source while the dose is given
    • The source should be immediately stored in its lead case once the dose is given

Radioactive Tracers

  • Radioisotopes can be used as ‘tracers’ to monitor the processes occurring in different parts of the body
  • Radioactive tracers with a short half-life are preferred because:
    • Initially, the activity is very high, so only a small sample needed
    • The shorter the half-life, the faster the isotope decays
    • Isotopes with a shorter half-life pose a much lower risk to the patient
    • The medical test doesn‘t last long so a half-life of a few hours is enough

 

  • One example is Iodine-131
    • This isotope is known to be specifically taken up by the thyroid gland making it useful for monitoring and treating thyroid conditions
    • It emits beta particles which means it will stay concentrated on the thyroid area and nowhere else in the body
    • It has a short half-life of 8 days meaning it will not be around too long to cause prolonged exposure
  • Another isotope commonly used as a tracer is Technetium-99m
    • It is a gamma emitter with an energy of about 140 keV which is ideal for detection
    • It has a half-life of 6 hours so it is ideal for use as a tracer, but will not remain active for too long and can be tolerated by the body
    • Gamma radiation is ideal as it is the most penetrating so it can be detected outside the body
    • Also, gamma is the weakest ioniser and causes minimal damage
    • As well as this, technetium-99m may be prepared easily at the hospital when required making it a cost-effective treatment

Sterilising Medical Equipment

  • Gamma radiation is widely used to sterilise medical equipment
  • Gamma is most suited to this because:
    • It is the most penetrating out of all the types of radiation
    • It is penetrating enough to irradiate all sides of the instruments
    • Instruments can be sterilised without removing the packaging
  • The general public might be worried that using gamma radiation in this way might cause the equipment itself to become radioactive, however, this is not the case because:
    • In order for a substance to become radioactive, the nuclei have to be affected
    • Ionising radiation only affects the outer electrons and not the nucleus
    • The radioactive material is kept securely sealed away from the packaged equipment so there is no chance of contamination
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