Health Physics: Nuclear Radiation

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Author:
crobertsonx
ID:
86640
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Health Physics: Nuclear Radiation
Updated:
2011-05-18 19:26:12
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Health Physics Nuclear Radiation
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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?
    alpha
  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

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