radioactivity

• what is contamoniation


  when an object has a radioactive material introduced into it
• what is irradiation


  when an object is exposed to a source of radiation outside the object
• uses for irradiation

  • medical- strrilisation of medical equipement, gamma rays used to kill deep tumours called gamma knife
  • sterlilisation- preserving fruit in supermarkets by exposing to radioactive source
• uses for contmination

  • medical- injected radioactive sources can be used as medical tracers
  • leaks- water supplies can be contaminated with gamma emitting radioactive sources to detect leaks
• differences between irradiation and contamiantion

  • in irradiation, radiation can be blocked and stops as soon as source is removed, object doesnt become radioactive
  • in contamination, once object is contaminated radiation cannot be stopped, harder to remove all contamination and a conatmainted object remains radioactive as long as source is present
• pros and cons of irradiation

  +sterlilisation can be done without high temp= cheaper

  +can be used to kill bacteria on objects which could melt

  -may not kill all bacteria

  -can be very harmful to stand in area where objects are irradiated as can cause mutation to cells
• pros and cons of contamination

  +radioactive isotopes can be used as medical and industrial traces

  +imager processes can replace invasive medical procedures

  -hard to ensure contamination is fully removed

  -exposure to radiactive materlais can cause dmage to healthy cells
• what is activity

  the maount of radiation emmitted from a radiocative source per second
• what is activty measured in

  Bq, beoqueral
• what is half life

  the time taken for a radiactive materials activity to decrease by half
• how do smoke detector alarms work?

  -uses alpha particles as do not penetrate far and are easily absorbed by smoke

  -source shuold have a long half life so smoke detector does not need to be replaced regularly

  -when smoke eneters between the metal plates , smoke absorbs some alph particles which causes less ionisation so a smaller than usual current flows and alarm sounds
• exmplain contamination to check for leask


  were their is a leak contaminated water seeps into the ground causing a build up of gamma emmissions in that area , the build up can then be detected by a geiger muller tube
• why do smoke alarms need long halflie

  • so they do not need to be replaced regularly
  • so count rate remains nearly contant everday
• what is count rate

  the number of decays each second
• what is nuclear fission

  when a large unstable nucleaus splits into 2 smaller duaghter nucei to release energy