P6.2

• what is contamination?

  the unwanted presence of material containing radioactive atoms on other material
• when is a substance radioactive?

  when it contains radioactive atoms that emit radiation
• when does contamination occur?

  when a radioactive isotope gets onto a material where it should not be

  • this is often due to a radiation link
• what is irradiation?

  the process of exposing a material to alpha, beta or gamma radiation
• what irradiation do?

  it doesnt make the material radiactive but it can kill living cells
• what is a use of irradiation?

  it can be used as a method of sterilisation

  • surgical equipment is irradiated before being used to kill any bacter on it
  • food can also be irradiated to kill any micro-organisms within it to make the food last longer without going mouldy
• differences between irradiation and contamination

  1. in irradiation, the object is exposed to radiation but does not become radioactive. in contamination, the object becomes radioactive and emits radiation
  2. in irradiation, the danger is from radiation emitted outside the object. in contamination, the danger from radiation is emitted within the object
  3. in irradiation, it can be prevented by using shielding such as lead clothing. contamination can be prevented by safe handling of sources and airtight safety clothing
• what happens when an isotope has a short life?

  the nuclei will decay very quickly

  • this means the isotope will emit a lot of radiation in a short amount of time
  • this can be dangerous
• what type of half life is used in medical tracers and why?

  short half life isotopes because the material will quickly lose its radioactivity
• what happens when an isotope has a long half-life?

  a sample of it will decay slowly

  • it will remain radioactive for a long time
• what is a tracer?

  a radioactice isotope that can be used to track the movement of substances like blood around the body
• what is usually used for medical tracers?

  gamma emitters

  • gamma rays are highly penetrating and so can pass through the body and be detected outside the body
  • this allows an internal image of the body to be created
• why is gamma rays also less harmful in medical tracers?

  gamma rays are less ionising
• what happens in radiotherapy?

  external: beams of gamma rays are directed at the cancerous tumour

  internal: small pellets of radioactive materials can be inserted into a tumour exposing it directly to radiation
• risks of radiation

  can kill and damage living cells

  can cause cancer

  can cause mutations
• what is nuclear fission?

  the splitting of a large, unstable nucleus into two smaller nuclei as well as 2 or 3 neutrons
• spontaneous fission

  when nuclei undergo fission without additional energy being put into the nucleus
• what is nuclear fusion?

  when two light nuclei join to form a heavier nucleus