nuclear fission and fusion

• Nuclear fission


  The splitting of a large nucleus to produce two smaller ones. Two or three neutrons are also released in the process.
• Nuclear reactor


  A piece of equipment in which nuclear fission or fusion takes place.
• Neutron


  Uncharged subatomic particle, with a mass of 1 relative to a proton.
• Daughter nuclei


  The nuclei (centres of atoms) that are produced by a nuclear reaction. In nuclear fission the parent nucleus splits into two smaller daughter nuclei and releases energy.
• Chain reaction


  A nuclear chain reaction occurs when a neutron splits a nucleus, releasing more neutrons, which in turn go on to split even more nuclei.
• Turbine


  Revolving machine with blades that are turned by wind, water or steam. Turbines in a power station turn the generators.
• Generator


  An electromagnetic device that produces electricity when it is turned on.
• The energy from the neutrons powers a nuclear reactor.
• The fast moving neutrons carry most of the energy from the reaction with them (99%) but before the neutrons can collide with fresh uranium nuclei, they need to be slowed down.
• Nuclear fission


  The splitting of a large nucleus to produce two smaller ones. Two or three neutrons are also released in the process. The energy from the neutrons powers a nuclear reactor.
• Fission reactor


  • Contains nuclear fuel (usually uranium or plutonium)
  • Contains a graphite core to slow down neutrons
  • Contains control rods to absorb excess neutrons and control the rate of the nuclear fission reactions
  • Contains a coolant to transfer thermal energy and drive turbines
  • Contains a concrete shield to protect against radioactive hazards
• An uncontrolled fission reaction is the basis of an atomic bomb
• Nuclear fusion


  The process of combining light atomic nuclei to form heavier nuclei, releasing a large amount of energy.
• Releasing the energy from nuclear fission and fusion would free the world from having to use fossil fuels
• Nuclear fusion


  The joining together of two smaller atomic nuclei to produce a larger nucleus. Radiation is released when this happens.
• Nuclear fusion


  • Happens in stars like our Sun, and in hydrogen bombs
• Nuclear fusion


  1. Two small, light nuclei join together to make one heavy nucleus

  2. Fusion reactions occur in stars where two hydrogen nuclei fuse together under high temperatures and pressure to form a nucleus of a helium isotope
• The simplest fusion reaction is when four hydrogen nuclei become one helium nucleus
• In nuclear reactions, a small amount of mass changes to energy
• Complete fusion of all hydrogen nuclei in a 250ml glass of water would release about 17,200,000,000,000 joules of energy
• The sun releases 3.8 × 10^26 joules of energy every second
• Repel


  Objects that tend to push apart because of a force between them
• For fusion to occur, the temperature of the hot gas or plasma needs to be at least 150,000,000 degrees Celsius