What Is Nuclear Fusion?

• Published date: 22 January 2024
• Subject Matter: Intellectual Property, Energy and Natural Resources, Energy Law, Oil, Gas & Electricity, Patent
• Law Firm: Maucher Jenkins
• Author: Arjun Grewal

Nuclear fusion is the process whereby two smaller atomic nuclei combine to form a larger nucleus. It is the opposite of fission whereby a larger nucleus splits into the two smaller ones. In each case energy is released. This release of energy is based on Einstein's principle of mass-energy equivalence (the famous E = mc²). In each case, there is a reduction of mass. A small change in mass is converted into a large release of energy. The energy released through nuclear fusion (e.g. a hydrogen bomb) is greater than the amount released in nuclear fission (e.g. the bomb released over Hiroshima in 1945).

Nuclear fusion only releases energy when the element is lighter than iron. The average binding energy per nucleon increases with atomic weight up to that of iron and falls thereafter with larger and larger atoms (see graph). Elements lighter than iron tend to fuse into larger elements. Those heavier than iron tend to split into smaller elements. Iron is considered the dead-end when it comes to nuclear fusion. This is why iron [Fe] is the final element produced in a collapsing star.

To put into perspective how much energy is being released in a fusion reaction, it takes four hydrogen atoms to form a single helium atom. The difference in mass in this reaction is 0.02862 atomic mass units. This mass change is extremely small, and the energy release (4.3 x 10^-12J) is also very small. But Avogadro's constant is enormous. One gram of matter contains 6.02 x 10²³ atomic mass units. Just 4 grammes of hydrogen being converted into helium would result in an energy release of 2.6 x 10⁸kj - enough to keep a 60-watt lightbulb powered for over a century.

If a fusion reaction could be controlled in a manner similar to a conventional nuclear fission reactor, a very a small amount of fuel could generate a large amount of energy and such a proposition could provide a secure source of energy for generations to come with no greenhouse gas emissions. These reactions take place in a tokamak. A tokamak is a machine in which fusion reactions can take place with the use of hot plasma.

Moreover, unlike uranium fission or plutonium fission, nuclear fusion does not generate heavy radioactive waste byproducts. These prospects - (i) CO₂-free energy from (ii) readily available light elements such as hydrogen or lithium with (iii) no radioactive waste - make fusion a very attractive prospect for the world's future energy needs. But there is a very big snag.

Nuclear fusion occurs naturally in...