Health Physics: Nuclear Radiation

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Health Physics: Nuclear Radiation
2011-05-18 19:26:12
Health Physics Nuclear Radiation

Health Physics: Section 5- Nuclear Radiation
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  1. how does radiation affect humans?
    it can kill or damage living cells
  2. what can nuclear radiation be used for?
    • to sterilise medical instruments by killing germs
    • to kill cancerous cells by placing an alpha source next to the tumour or by firing a beam of gamma rays at the tumour
  3. radiation can be used for diagnosis, how?
    • a radiactive tracer is injected into the patient
    • the tracer is carefully chosen so that is will collect in the organ being studied and an image of the organ can be then be taken with a gamma camera
  4. what is an atom?
    • the smallest particle into which matter can be divided
    • its made up of a central nucleus with orbiting electrons
  5. what are the three types of nuclear radiation?
    • alpha
    • beta
    • gamma
  6. what happens what radiation passes through a material?
    • some of its energy is absorbed by the material.
    • the amount of absorption depends on the type of radiation and the material it is passing through
  7. in an atom, what does the nucleus consist of?
    • positively charged protons
    • uncharged neutrons
  8. in an atom, what does the electrons do?
    • orbit the nucleus at high speed
    • they are negatively charged
  9. what is alpha absorbed by? what is its range in air?
    • sheet of paper
    • 20cm
  10. what is beta absorbed by? what is its range in air?
    • 2-3mm aluminium
    • a few metres
  11. what is gamma absorbed by? what is its range in air?
    • 2-3cm lead
    • not aborbed in air
  12. what is ionisation?
    adding or taking away an electron from an uncharged atom
  13. what is photographic fogging?
    • its used in to detect radiation in a film badge
    • in a film badge different section of a piece of photographic film are covered by various thicknesses and types of absorber
  14. which radiation causes more ionisation?
  15. what is ionisation used to detect radiation from?
    the Geiger-Muller tube
  16. what happens in the Geiger-Muller tube?
    • when radiation enters the tube through the thin mica window it causes ionisation in the gas
    • this allows the gas to conduct and a pulse of current passes between the electrodes
    • this pulse of current is counted by the counter
  17. how can the type of radiation be determined?
    • by which sections of the film in a film badge are blackened
    • the amount of radiation can be determined by how black the film is
  18. what is scintillation?
    • radiation can cause some materials to scintillate.
    • the material absorbs the energy of the radiation and re-emits it as light.
  19. scintillation is used to detect radiation in what?
    gamma camera
  20. what is a collimator?
    • a large piece of lead with thousands of holes in it
    • ensures that although gamma rays are given off in all directions, only parallel rays reach the detector
  21. what is a detector?
    converts radiation into light by scintillation
  22. what is the electronics?
    turn the pattern of light into an electrical signal, which can then be transmitted to a monitor for viewing
  23. what is the activity of a radioactive source?
    the number of atoms that decay each second
  24. what is the half-life of a radioactive source?
    the time taken for its activity to half
  25. what is the activity of a radioactive source measured in?
    Becquerels, Bq
  26. how can the half-life of a radioactive source be measured?
    by taking measurements of the activity of the source at regular intervals of time using a Geiger-Muller tube and counter
  27. what happens to the activity of a radioactive source?
    decreases with time
  28. what safety precautions need to be taken when handling radioactive materials?
    • always handle with forceps
    • point source away from body
    • store in lead container
    • label all sources
    • wash hands after use
  29. what is the dose equivalent of a radioactive source?
    a measure of the biological risk of the source
  30. what is dose equivalent measured in?
    Sieverts, Sv
  31. what does the biological effect of radiation depend on?
    • the type of absorbing tissue
    • the type of radiation
    • the total energy absorbed