nuclear radiation

• Radioactive decay


  The process in which unstable atomic nuclei break apart or change, releasing radiation as they do so
• Unstable nucleus


  • Can decay by emitting an alpha particle, a beta particle, a gamma ray or a single neutron
• Alpha particle


  A 'package' of two protons and two neutrons (the same as a helium nucleus)
• Alpha decay


  Causes the mass number of the nucleus to decrease by four and the atomic number to decrease by two
• Beta particle


  A fast-moving electron emitted when a neutron turns into a proton
• Beta decay


  Causes the atomic number of the nucleus to increase by one and the mass number to remain the same
• Gamma ray


  An energetic electromagnetic wave emitted as the nucleus 'cools down' after emitting an alpha or beta particle
• Gamma ray emission


  Causes no change in the number of particles in the nucleus, so the atomic number and mass number remain the same
• Neutron emission


  Causes the mass number of the nucleus to decrease by one and the atomic number to remain the same
• Properties of nuclear radiations

  • Penetrating power
  • Ionising power
  • Range in air
• Alpha radiation


  • Penetrating power: Skin/paper
  • Ionising power: High
  • Range in air: < 5 centimetre (cm)
• Beta radiation


  • Penetrating power: 3 mm aluminium foil
  • Ionising power: Low
  • Range in air: ≈ 1 metre (m)
• Gamma radiation


  • Penetrating power: Lead/concrete
  • Ionising power: Very low
  • Range in air: > 1 kilometre (km)
• All types of radioactive decay can be detected by a Geiger-Muller tube
• Penetrating power


  The power of the radiation that demonstrates how far into a material the radiation will go
• Ionising power


  The power of radiation to convert an uncharged atom or molecule into a charged particle by adding or removing electrons
• Alpha radiation (α)


  • Penetrating power: Skin/paper
  • Ionising power: High
  • Range in air: < 5 centimetre (cm)
• Beta radiation (β)


  • Penetrating power: 3 mm aluminium foil
  • Ionising power: Low
  • Range in air: ≈ 1 metre (m)
• Gamma radiation (γ)


  • Penetrating power: At least 40 mm lead or 2 m concrete
  • Ionising power: Very low
  • Range in air: > 1 kilometre (km)
• Use of alpha radiation


  • In smoke detectors
• A source of alpha radiation is used in smoke detectors because the range is very low and alpha radiation has a very high ionising power
• People are exposed to sources of radiation in all aspects of everyday life
• Radioactive sources can be very useful but need handling carefully to ensure safety
• Radioactive


  Unstable atoms that give off particles that can be harmful to humans
• Irradiation for sterilisation


  1. Expose fruit to a radioactive source (typically cobalt-60)

  2. Gamma rays emitted destroy any bacteria on the fruit

  3. Does not cause the fruit to become radioactive
• Sterilisation


  The process of ensuring that a sample contains no living things
• Medical irradiation


  1. Sterilise surgical instruments

  2. Use beams of gamma rays to kill cancerous tumours

  3. Careful calculations to establish the best dose - enough to kill the tumour but not so much to damage healthy tissue

  4. Gamma knife used to kill cancerous cells in the brain
• Radioactive sources in medical applications

  • Consider the nature of decay (alpha, beta or gamma)
  • Consider the half-life (long enough for useful measurements, short enough to decay to safe levels soon after use)
  • Consider toxicity
• Irradiation may not kill all bacteria on an object and can be very harmful, exposing people's cells to damage and mutation
• Tracer


  A radioisotope used to trace, eg the flow of blood through an organ
• Isotope


  Atoms of an element with the same number of protons and electrons but different numbers of neutrons
• Emitted


  Energy is 'given-out' by the material and the internal energy of the material will decrease
• Contamination to check for leaks

  1. Contaminate water supply with a gamma-emitting radioactive isotope

  2. Build-up of gamma emissions in area of leak can be detected using a Geiger-Müller tube

  3. Isotope must be a gamma emitter, have a half-life of at least several days, and not be poisonous to humans
• Advantages of contamination


  • Radioactive isotopes can be used as medical and industrial tracers
  • Use of isotopes with a short half-life means exposure can be limited
  • Imaging processes can replace some invasive surgical procedures
• Disadvantages of contamination


  • Radioactive isotopes may not go where they are wanted
  • It can be difficult to ensure that the contamination is fully removed so small amounts of radioisotope may still be left behind
  • Exposure to radioactive materials can potentially damage healthy cells
• Radioactive materials are hazardous
• Nuclear radiation


  Particles or waves given out by the nucleus of an unstable atom. Alpha particles, beta particles and gamma waves are the three most common types of nuclear radiation.
• Ionise


  To convert an uncharged atom or molecule into a charged particle by adding or removing electrons
• Nuclear radiation can ionise chemicals within a body, which changes the way the cells behave. It can also deposit large amounts of energy into the body, which can damage or destroy cells completely.
• Effects of radiation on the human body

  • Eyes: High doses can cause cataracts
  • Thyroid: Radioactive iodine can build up and cause cancer, particularly during growth
  • Lungs: Breathing in radioisotopes can damage DNA
  • Stomach: Radioactive isotopes can sit in the stomach and irradiate it for a long time
  • Reproductive organs: High doses can cause sterility or mutations
  • Skin: Radiation can burn skin or cause cancer
  • Bone marrow: Radiation can cause leukaemia and other diseases of the blood