Radiation

Radiation

Uses of radiation
1. Smoke Detectors
  1. Uses alpha radiation
  2. A weak source of alpha radiation is placed in the dectector close to two electrodes
    1. The source causes ionisation and a current flows between the electrodes
  3. If there is a fire then smoke will absorb the radiation so the current stops and the alarm sounds
2. Tracers in Medicine
  1. Always short half life beta or gamma emitters
  2. Certain radioactive isotopes can be injected into people (or they can swallow them) and their progress around the body can be followed using an external detector. A computer converts the reading to a display showing where the strongest reading is coming from
  3. A well known example is the use of iodine-131 which is absorbed by the thyroid gland just like normal iodine-127 but it gives out radiation which can be detected to indicate whether the thyroid gland is taking in iodine as it should
  4. All isotopes which are taken into the body must be gamma or beta emitters (never alphas) so that the radiation passes out of the body and they should only last a few hours so that the radioactivity inside the patient disappears quickly i.e. they have a short half life
3. Radiotherapy
  1. the treatment of cancer using gamma rays
  2. Since high doses of gamma rays will kill all living cells they can be used to treat cancers
  3. The gamma rays have to be directed carefully and at just the right dosage so as to kill the cancer cells without damaging too many normal cells
  4. However a fair bit of damage is inevitably done to normal cells which makes the patient feel very ill
4. Sterilisation of food and surgical instruments
  1. Using gamma rays
  2. Food can be exposed to a high dose of gamma rays which will kill all microbes keeping the food fresh for longer
  3. Medical instruments can be sterilised in just the same way rather than by boiling them
  4. The great advantage of irradiation over boiling is that it doesnt involve high temperatures so things like fresh apples or plastic instruments can be totally sterilised without damaging them
  5. The food is not radioactive afterwards so its perfectly safe to eat
  6. The isotope used for this needs to be a very strong emitter of gamma rays with a reasonably long half life (several months) so that it doesnt needs replacing too oftem
Radioactivity Safety
1. Radiation harms living cells
  1. Alpha, beta and gamma radiation will cheerfully enter living cells and collide with molecules
    1. These collisions cause ionisation which damages or destroys the molecules
  2. Lower doses tend to cause minor damage without killing the cell this can give rise to mutant cells which divide uncontrollably. This is cancer
  3. Higher doses tend to kill cells completely which causes radiation sickness if a lot of body cells completely which causes radiation sickness if a lot of body cells all get blatted at once
    1. The extent of the harmful effects depends on two things
      1. How much exposure you have to radiation
      2. The energy and penetration of the radiation since some types are more hazardous than others
2. Outside the body beta and gamma sources are the most dangerous
  1. This is because beta and gamma can get inside to the delicate organs whereas alpha is much less dangerous because it cant penetrate the skin
3. Inside the body an alpha source is the most dangerous
  1. Inside the body alpha sources do all their damage in a very localised area. Beta and gamma sources on the other have are less dangerous inside the body because they mostly pass straight out without doing much damage
4. Safety Precautions
  1. When conducting experiments use radioactive sources for as short a time as possible so your exposure is kept to a minimum
  2. Never allow skin contact with a source. Always handle with tongs
  3. Hold the source at arms length to keep it as far from the body as possible. This will decrease the amount of radiation that hits you especially for alpha particles as they dont travel far in air
  4. Keep the source pointing away from the body and avoid looking directly at it
  5. Lead absorbs all three types of radiation (though a lot of it is needed to stop gamma radiation completely) always store radioactive sources in a lead box and put them away as soon as the experiment is over. Medical professionals who work with radiation every day wear lead aprons and stand behind lead screens for extra protection
  6. When someone needs an X-ray or radiotherapy only the are of the body that needs to be treated is exposed to radiation. The rest of the body is protected with lead or other radiation absorbing materials

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