Topic 6

• Describe the advantages of nuclear power for

  generating electricity

  ● Nuclear fuels do not produce carbon dioxide

  ● The fuel is readily available, so would reduce strain on the

  fossil fuel supplies

  ● Less nuclear fuel has to be used to produce the same

  amount of energy as burning fossil fuel

  ● Does not contribute to global warming
• Explain some disadvantages of using nuclear power

  to generate electricity.

  ● Unpopular - the public perceive nuclear power as very dangerous

  ● Security risks as the radioactive substances can be useful for

  terrorists

  ● Expensive to commission and decommission the stations - which may

  be bad for a country’s economy

  ● The radioactive waste can be difficult to dispose of and will remain

  radioactive for many years - which can be dangerous to humans and

  the environment

  ● Risk of nuclear accidents
• What is nuclear fission?

  The splitting of large, unstable nuclei to

  form smaller more stable nuclei (+ the

  emission of spare neutrons).
• What usually needs to happen to induce

  fission?

  ● The unstable nuclei must absorb a

  neutron

  ● Spontaneous fission (where no

  neutron absorption occurs) is rare
• Alongside two smaller nuclei, what else is emitted in

  a fission reaction?

  ● Two or three neutrons

  ● Gamma rays

  ● Energy
• Name a common fissile nuclei.

  Uranium-235
• What are the three main components of the core a

  nuclear reactor?

  Fuel rods, control rods and a moderator
• What takes place during a chain reaction in a

  nuclear reactor?

  ● An unstable nucleus absorbs a neutron

  ● The nucleus undergoes fission and

  releases 2 or 3 further neutrons

  ● These induce more fission, which results

  in a chain reaction
• What is the consequence of an uncontrolled chain

  reaction?

  ● The rate of fission events becomes to

  high and results in the production of

  too much energy

  ● This can lead to a nuclear explosion
• How is the chain reaction in a fission reactor kept

  under control?

  ● Control rods are positioned in between the fuel

  rods

  ● The rate of fission is controlled by moving

  these rods up and down

  ● The lower the rods are inserted, the slower the

  rate of fission
• What is the role of the moderator in a nuclear

  reactor?

  To slow down the neutrons so they are

  travelling at speeds which allow them to

  be absorbed by fissile nuclei and cause

  fission
• How is electricity is produced in a nuclear power

  station?

  ● The reactions release thermal energy

  ● The thermal energy is used to boil water and

  then produce steam.

  ● This steam is then used to turn a turbine which

  starts the generator
• What is nuclear fusion?

  When two light nuclei join to produce a

  heavier nucleus and release energy.
• Name two isotopes of hydrogen which

  are commonly used in nuclear fusion.

  Deuterium and Tritium
• Which releases more energy, nuclear

  fission or nuclear fusion?

  Nuclear fusion.
• Explain the difficulty of generating energy through

  nuclear fusion

  Fusion requires very high temperatures

  which in itself requires large quantities of

  energy. Currently, the production of

  fusion results in a net loss of energy
• Give an example of where fusion

  occurs?

  In the sun - stars use fusion as their

  energy source.
• Why does nuclear fusion require so much energy?

  This is because both nuclei are positive

  therefore a lot of energy is required to

  overcome the electrostatic repulsion

  between the two nuclei.
• Activity

  The rate at which a source of unstable nuclei decays
• The unit of radioactive activity is Becquerel (Bq)
• Count-rate


  The number of radioactive decays per second for a radioactive source
• Detector that may be used to measure count-rate

  • Geiger-Muller tube
• Radioactive decay

  • Random
  • Which nuclei decays and when is determined only by chance
  • It is impossible to predict which nuclei will decay and when
• Half-life


  • The time it takes for the number of unstable nuclei in a substance to halve
  • The time it takes for the count rate from a sample to fall to half its initial level
• Types of nuclear radiation

  • Alpha particles
  • Beta particles
  • Gamma rays
  • Neutrons
• Background radiation

  Radiation that is always present, in very small amounts and so not harmful
• Sources of background radiation

  • Rocks
  • Cosmic rays from space
  • Nuclear weapon testing
  • Nuclear accidents
• Measuring and detecting background radiation

  1. Photographic film

  2. Geiger-Muller counter
• Photographic film used to measure radiation

  Photographic film turns dark when it absorbs radiation, allowing workers to know when they have been exposed to too much radiation
• Geiger-Muller tubes used to measure radiation


  When the Geiger-Muller tube absorbs radiation it produces a pulse, which a machine uses to count the amount of radiation. The frequency of the pulse depends on how much radiation is present.
• Alpha particle

  Two protons and two neutrons, the same as a helium nucleus
• Range of alpha particle through air

  A few centimetres (normally in the range of 2-10cm)
• What blocks beta radiation

  A thin sheet of aluminium, several metres of air
• What blocks gamma radiation

  Several centimetres of lead, a few metres of concrete
• Most ionising radiation

  Alpha radiation
• Least ionising radiation

  Gamma radiation
• Effect of gamma emission on mass/charge of atom

  Both mass and charge remain unchanged
• Plum-pudding model of the atom

  A sphere of positive charge, with the negatively charged electrons distributed evenly throughout it
• Prior to the discovery of the electron, the atom was believed to be indivisible
• Experiment that led to the plum-pudding model being discarded

  Rutherford's alpha-Scattering experiment