radioactivity

• Radioactivity is the process by which unstable atomic nuclei lose energy by emitting radiation
• Ionisation is the process of converting an atom or molecule into an ion by adding or removing charged particles
• Penetration power of radiation:

  • Alpha particles (helium 4,2): high penetration power
  • Beta particles (electron 0, -1): medium penetration power
  • Gamma rays: low penetration power
• Nuclear equation example:

  • Iridium-192 decays into platinum by emitting a beta particle
  • 192Ir —> 192Pt + beta- (77 -> 78, -1)
• Background radiation sources:

  • Cosmic radiation: 10%
  • Man-made sources: 15%
  • Biological sources: 10-15%
  • Ground/rock sources: 10-15%
  • Radon gas: 50%
• Methods to measure radioactivity:

  • Film badges
  • Geiger-Muller tube (counts per second)
  • To get an accurate result, use the Geiger-Muller tube by following steps:

  1. Remove the radioactive source

  2. Measure the background count

  3. Repeat the measurement

  4. Subtract the background count value from the reading
• Activity is the rate of decay of a radioactive substance
• Half-life is the time taken for the number of decays/activity to halve
• Uses of radioactivity:

  • Medical tracer: gamma rays
  • Radiotherapy:
  • Gamma rays for external treatment
  • Beta particles for internal treatment
  • Minimizing irradiation risks:
  • Use precautions like gloves, tongs
  • Keep time exposure short
  • Store radioactive sources in lead containers
  • Maintain distance exposure far
  • Wear protective clothing
• Nuclear fusion: fusing two atoms into one large atom

  • Nuclear fission: splitting one atom into two atoms
  • Steps in fission:

  1. Fire neutron at unstable nucleus

  2. Nucleus splits into two daughter nuclei

  3. Released neutron

  4. Kinetic energy released

  5. Released neutron hits further nuclei

  6. Chain reaction

  7. Moderator slows down neutron

  8. Control rod absorbs neutron
• Components in a nuclear reactor:

  • Fuel rod: uranium-258, for fission
  • Moderator: water/graphite, to slow down neutrons for easier nucleus splitting
  • Control rod: boron, to absorb neutrons and control the rate of production
  • Coolant: water/gas, circulates around fuel rods to carry heat energy
  • Shielding: concrete/lead, prevents particles and energy from radioactive decay from escaping the nuclear reactor