Fusion (SQA National 5 Physics): Revision Note

Fusion

• Nuclear fusion is defined as:

The process where two small nuclei combine to form a larger nucleus

Fusion of two nuclei

• Massive amounts of energy are released in the process of nuclear fusion

  • Far more energy than fission or any chemical reaction for a similar mass of reactants

Conditions of nuclear fusion

• Nuclear fusion requires specific conditions:

  • Extremely high temperatures

  • Extremely high pressures

  • Plasma must be contained

• Stars, like the Sun, have the required conditions for fusion reactions

• Stars use nuclear fusion reactions in their core to release energy

  • Smaller hydrogen nuclei are combined to form larger helium nuclei, releasing massive amounts of energy in the process

Plasma containment

• Plasma is the name given to extremely hot, electrically charged gas

• In a fusion reaction, the plasma consists of small nuclei (such as isotopes of hydrogen)

• To keep the plasma hot enough for fusion, it cannot touch the sides of the fusion reactor, or it will cool down

• Since the plasma is charged, its motion is controlled using magnetic fields

• The plasma must be contained in this way long enough for fusion to occur

A plasma containment fusion reactor

Fusion and energy production

• It is theoretically possible to produce a fusion reactor that could be used to generate electricity

  • This technology could potentially solve the world's energy crisis

• Currently, the longest sustained fusion reaction was 20 minutes

• Scientists are working on fusion, but it is not yet a viable way to produce electricity