Fission and Fusion

• Nuclear fission is when a large and unstable nucleus splits into two smaller nuclei, releasing large amounts of energy and a neutron.
• What are the products from nuclear fission?

  Large amounts of energy and neutrons
• When the nuclei splits into two during nuclear fission, what are they called?

  Two daughter nuclei
• What type of energy are in the stores of the fission products?

  Kinetic energy stores in the daughter nuclei and neutrons
• In a nuclear reactor, the kinetic energy is transferred to thermal energy stores to help produce steam to drive a turbine.
• Nuclear reactor diagram:

  A)

  B)

  C)

  D)

  E)

  F)

  
• What do the moderators in a nuclear reactor do?

  The moderator, usually graphite or water helps to slow down neutrons
• What are control rods often made out of?

  Boron
• What do control rods do?

  The boron control rods help to limit the rate of fission by absorbing excess neutrons
• What is the shielding made out of?

  Thick concrete structure which may contain lead or other metals.
• When the reactor is producing energy at the correct rate, what two factors must be controlled?

  1. The number of free neutrons in the reactor
  2. The energy of the free neutrons
•  The overall purpose of the nuclear reactor is to collect the heat energy produced from nuclear reactions
• Shielding is to absorb hazardous, ionising radiation
• Most radioactive waste from nuclear power stations, and hospitals is 'low level.'
• How do nuclear reactors generate electricity?

  The water turns to steam, which turns a turbine, which turns a generator and generates electricity
• What happens in the nuclear reactor?

  A substance e.g; CO2 is pumped around the reactor and transfers the energy (by heating) to the water in the heat exchanger.
• Nuclear Fusion is when two light nuclei collide at high speed and fuse to creat a larger, heavier nucleus.
• • The energy produced during nuclear fusion comes from a very small amount of the particle’s mass being converted into energy
• Stars, including the Sun, use nuclear fusion to produce energy for example the hydrogen atoms fuse to make helium atoms and energy.
• Two hydrogen nuclei are fusing to form a helium nuclei

  A) Nuclei

  B) Nuclei

  C) Nuclei

  D) product

  
• The conditions for fusion are: 


  1. Very high temperature of fuel
  2. Very high kinetic energy of nuclei to overcome repulsion
  3. Very high density/pressure to increase the possibility of suitable collisions
• Why do protons repel each other?

  They are positively charged. Thus, they have electrostatic repulsion
• How do you overcome electrostatic repulsion in fusion?

  High kinetic energy from high temperatures in order for the protons to be travelling towards each other at very high speeds