Radioactivity #2

Radioactivity #2

1. Uses of Nuclear Radiation

   • Medical tracers use beta or gamma radiation
     • Beta and gamma will penetrate the skin
     • Needs a short half-life
   • Radiation is used to treat cancer
     • Ionising radiation can also be used to treat the cancer
       • Radiotherapy kills the cancer cells and stop them dividing
   • Food and equipment can be sterilised using gamma rays
     • Food can be irradiated with a high dose of gamma rays to kill all microbes
       • Medical equipment can be sterilised using gamma rays
         • Long-half life so it doesn't need replacing too often
   • Radiation is used in industry for tracers and thickness gauges
     • Gamma emitting tracers are used in industry to detect leaks in underground pipes
     • Should have a short half-life - won't cause long-term hazard if it collects somewhere

2. Risks from Nuclear Radiation

   • Ionising radiation can damage cells and tissue
     • Beta and gamma can penetrate the skin and soft tissues to reach the organs inside the body
       • Lower doses cause minor damage without killing the cell
         • This can cause mutations in cells which become cancer
   • Irradiation
     • Exposure to radiation is called irradiation
     • Objects near a radioactive source are irradiated by it. This means they're exposed to it
     • Irradiating something does not make it radioactive
     • Keeping sources in lead-lined boxes are all ways of reducing the risk of irradiation
   • Contamination
     • Contamination is radioactive particles getting into jobs
     • These contaminating atoms might then decay, releasing radiation which can cause harm
   • Radioactive waste
     • Most waste is low level and can be disposed of by burying it
     • High level waste is very dangerous
       • It stays radioactive for a very long time
     • It's difficult to find suitable places to bury the high level waste
       • This site has to be geologically stable away from soil, plants, rivers etc

3. Nuclear Fission

   • 1. Nuclear fission is the splitting of an atom. It can be spontaneous
   • 2. If a slow-moving neutron is absorbed, the nucleus is split
   • 3. Each time this happens, it spits out a small number of neutrons
   • 4. When it splits, it will form 2 daughter nuclei
   • 5. The new nuclei are usually radioactive

4. Nuclear Reactors

   • 1. The neutrons released by fission reactions have a lot of energy
     • 2. The moderator slows down neutrons
       • 3. Control rods limit the rate of fission by absorbing excess neutrons
       • 4. The high energy neutrons and gamma rays released in fission are high penetrating ionising radiation
         • 5. Shielding has to be used to absorb the ionising radiation
           • 6. A substance pumped round the reactor transfers the energy to the water in the heat exchanger
             • 7. The water turns to steam, turning a turbine, turning a generator and generates electricity

5. Nuclear Fusion

   • Nuclear fusion is the opposite of nuclear fission
     • 1. 2 light nuclei at high speed and fuse together to create a larger, heavier nucleus
       • 2. This heavier nucleus doesn't have as much mass as the two separate, light nuclei did
         • 3. Some of the mass of the light nuclei is converted to energy and is released as radiation
           • 4. Fusion releases a lot of energy
             • 5. Fusion only happens at really high pressures and temperatures
               • 6. This is because the positively charged nuclei have to get very close to fuse. They need to be moving very fast to overcome the strong force due to electrostatic repulsion
                 • 7. The temperatures and pressures needed for fusion are so high that fusion reactors are really hard and expensive to build