Definitions- fission and fusion

• Chain reaction


  A reaction where the products of one reaction causes another reaction
• Control rods


  Boron or cadmium rods that can be lowered into a reactor to control the rate of fission. They absorb neutrons to prevent them causing a chain reaction
• Daughter nuclei


  The main product of nuclear fission. Each daughter nucleus contains some of the protons and neutrons form the original parent nucleus
• Electrostatic repulsion


  The force experienced by a charged particle when it moves close to another particle of the same charge. For example two protons both repel as they are both positive
• Fission


  The splitting of a nucleus through absorption of a slow moving neutrons. Produces 2-3 more neutrons and daughter nuclei
• Fuel rods


  Rods of radioactive uranium or plutonium pellets inside a nuclear reactor. This is where fission takes place.
• Fusion


  The creation of a heavier nucleus by combining two smaller nuclei. This process requires a large amount of energy to overcome electrostatic repulsion
• Kinetic energy


  Energy that is expressed through the movement of particles
• Moderator


  Water or graphite. The part of a nuclear reactor that slows down high speed neutrons without absorbing them. Ready to be absorbed by a nucleus.
• Neutron 


  A subatomic particle found in the nucleus. It has in charge and is similar in size and mass to a proton.
• Nucleus 


  The centre/core of an atom. Contains neutrons and protons. Has a positive charge.
• Radioactive Decay


  The emission of an Alpha/Beta particle, neutron or gamma ray from an unstable nucleus. This can make the nucleus more stable.
• Reactor 


  The housing for nuclear fission Surrounded by concrete. Inside are all the components of a nuclear reactor
• Shielding 


  Thick layers of concrete that can protect the operator from ionising radiation