Nuclear Fusion
- Small nuclei can react to release energy in a process called nuclear fusion
- Nuclear fusion is defined as:
When two light nuclei join to form a heavier nucleus
- This process requires extremely high temperatures to maintain
- This is why nuclear fusion has proven very hard to reproduce on Earth
- Stars use nuclear fusion to produce energy
- In most stars, hydrogen atoms are fused together to form helium and produce lots of energy
Two hydrogen nuclei are fusing to form a helium nuclei
- The energy produced during nuclear fusion comes from a very small amount of the particle’s mass being converted into energy
- Albert Einstein described the mass-energy equivalence with his famous equation:
E = m × c2
- Where:
- E = energy released from fusion in Joules (J)
- m = mass converted into energy in kilograms (kg)
- c = the speed of light in metres per second (m/s)
- The amount of energy released during nuclear fusion is huge:
- The energy from 1 kg of hydrogen that undergoes fusion is equivalent to the energy from burning about 10 million kilograms of coal
- Designing a working fusion power station which produces more power than it uses is a major goal in engineering
- ITER in France is currently the best performing fusion power station, almost giving out as much energy as it requires to power it
- For fusion in a power station, deuterium and tritium, heavy isotopes of hydrogen are used
The fusion of deuterium and tritium to form helium with the release of energy
Worked example
An example of a hydrogen fusion reaction which takes place in stars is shown here.
Which of the following is a valid reason why hydrogen fusion is not currently possible on Earth?
A Hydrogen fusion produces dangerous radioactive waste
B Hydrogen nuclei require very high temperature to fuse together
C Hydrogen is a rare element that would be difficult to get large amounts of
D Hydrogen fusion does not produce enough energy to be commercially viable
ANSWER: B
-
- Hydrogen nuclei have positive charges
- So two hydrogen nuclei would have a repulsive force between them
- High temperatures are required to give the nuclei enough energy to overcome the repulsive force
- The answer is not A because the products of the hydrogen fusion shown in the reaction is helium
- Helium is an inert gas
- The answer is not C because hydrogen is a very abundant element
- It is the most common element in the universe
- The answer is not D because hydrogen fusion would produce a huge amount of energy
