Uses of radiation

• Medical tracers use beta or gamma radiation because they penetrate the skin and other body tissues.
• How do medical tracers work?

  1. The patient gets an injection or swallows the beta/gamma radiation source
  2. The radiation penetrates the body tissues and can be detected externally using a detector and computer to display the progress
• Doctors use medical tracers to check whether the organs are working as they should be.
• The radioactive source for medical tracers need to have half-life, so that the initial levels are high enough to be detected but the radioactivity in the patient quickly disappears.
• Why do we not use alpha particles for medical tracers?

  1. Useless - won't be detected outside because stopped by body's tissues
  2. Worse - Harmful because it's strongly ionising and harmful when inside.
• Radiation is used to treat cancer which is called radiotherapy.
• Radiotherapy kills cancer cells and stops them from dividing, it involves high doses of gamma rays carefully directed to kill cells in the tumour while minimising the dose to the rest of the body.
• What type of radiation does radiotherapy use?

  Gamma rays
• Food and equipment can be sterilised using Gamma rays
• Food can be irradiated with high doses of gamma rays to kill all microbes, so it doesn't go bad as quickly as it would otherwise.
• Why is irradiation good for sterilisation?

  It doesn't involve high temperatures like boiling equipment or food so, it can be sterilised without being damaged
• The radioactive source used for sterilisation needs to be very strong emitter and long half-life (several months) so, it does not need replacing too often.
• Radiation is used in industry for tracers and thickness gauges.
• Industry tracers which use gamma rays help to detect leaks in underground pipes.
• When using industrialised tracers, the source is flowing down the pipe and a detector is used above the ground.
• Why are gamma rays used for industrial tracers?

  Gamma can pass through any rocks surrounding the pipe.
• If there's a crack in the pipe, there will be more radiation collected outside the pipe and the detector will show extremely high radioactivity at that point.
• Gamma source used for industrial tracers should have short half-life to not cause a long-term hazard
• Beta radiation is used for thickness control in industry.
• How do thickness gauges work for industries?

  1. You direct radiation through the stuff being made (paper), and put a detector on the other side, connected to a control unit
• What happens if the paper coming out from the thickness gauge is too thick or thin?

  The radiation level will change and the control unit will adjust the rollers to give the correct thickness.
• Why do thickness gauges need to be a beta source?

  The paper will partly block alpha radiation, while gamma rays - all of them will go through it and the reading won't change if the thickness changes.
• What happens when the detected radiation level changes in thickness gauges?

  The control unit will adjust the roller to give correct thickness.