Nuclear fusion: Is it as good as it sounds?

Nuclear fusion has long been sought after as the next step in clean energy. A form of nuclear energy, fusion is being actively researched, due to its potential of being able to generate vast amounts of energy, if successfully implemented. However, is fusion really all that it is made out to be? If we are able to figure it out, will we really be able to solve our energy problems? Let’s try and answer some of those burning questions here.

Nuclear fusion is a type of energy process, where light elements, such as hydrogen, can “fuse” together to form heavier elements and releasing energy. It is the process by which stars, such as our Sun, fuel themselves. Given how we can feel the suns heat so far on Earth, it is no wonder why we are so keen on this producing energy this way.

Fusion is a process which is distinct from nuclear fission. Nuclear fission is the process which powers all nuclear reactors nowadays, and work on the reverse principle: heavier elements are split into lighter ones, thereby releasing energy. Unlike fission reactors however, a fusion reactor would not release any radioactive waste, and unlike fossil fuels, it does not produce CO₂ emissions. These two processes can be seen in the so called binding energy per nucleon curve.

The elemental symbol for Iron is Fe, this Iron-56 is seen as Fe-56 here. Source: https://commons.wikimedia.org/wiki/File:Binding_energy_curve_-_common_isotopes.svg

Without going into too much detail, a nuclear reaction can only occur when the there is an increase in the binding energy between the reactants and products. Thus we can identify two regions of the curve where this is possible: going from right to left until Iron-56 is where fission is possible, whereas going from left to right until Iron-56. The former is the region fission is allowed, whereas the latter is the region where fusion is possible. From this graph, we can also see why we want nuclear fusion. Namely the difference in energy between going from left to right versus right to left shows that a nuclear fusion reaction will release much more energy than a nuclear fission reaction.

The discussion and experimentation of fusion technology began around the same time as fission. The first fusion experiments took place around the  1930’s, and various technologies were first developed before an actual fusion reactor could be built (e.g. ways in which to confine the immense temperature and pressure of the plasmas generated in such a reaction). The first major breakthrough came through in late 1960, where Soviet scientists built the first Tokamak reactor [1]. This donut shaped reactor is able to confine the plasma using very strong magnetic fields [3]. The so called T1 inspired the design of almost all modern day fusion reactors, and Tokamak reactors are now the norm for any fusion reactor.

Fusion reactors continued to improve, and designs such as the Joint European Torus (JET) and the Japanese JT-60 set the standard with novel technologies, breaking records for sustained fusion reactions and temperature limits. One of the most recent records was set just last year in February 2024, when the JET reactor released 69 megajoules of energy in a single pulse [2].

The question is therefore, why haven’t we been able to produce reliable fusion energy? The answer to the question is complicated, but essentially it is because mimicking the conditions on the sun, to then control and manipulate that energy for our purposes, is incredibly, incredibly hard. It was only at the end of 2022 when scientists at the National Ignition Facility were able to reach the so called breakeven point, i.e. they were able to produce more energy than it consumed. In addition to this, many other challenges remain, such as manufacturing the materials which are able to withstand the incredible  forces which occur in a fusion reactor, producing the fuel which is not naturally abundant, or even just optimising how efficiently the heat can be removed from the reaction [4]. It is clear that there are still huge hurdles we need to get over before fusion energy becomes commonplace.

One of the biggest upcoming initiatives for fusion is the International Thermonuclear Experimental Reactor (ITER). This international collaboration seeks to design and implement the first fusion reactor at power plant production scales. The reactor has been decades in the making, and is currently under production, set to be ready to experiments in the mid 2030’s [5]. While fusion power might still be decades away, and many challenges still remain, suffice it to say, fusion power will have the potential change our world.

[1] “60 years of progress,” ITER.org, Nov. 10, 2023. https://www.iter.org/fusion-energy/60-years-progress

[2] E. Stallard, “Nuclear fusion: new record brings dream of clean energy closer,” www.bbc.com, Feb. 08, 2024. Available: https://www.bbc.com/news/science-environment-68233330

[3] “What is a tokamak?,” ITER.org, Jun. 16, 2023. https://www.iter.org/machine/what-tokamak

[4] “Making It Work,” ITER.org, Nov. 13, 2023. https://www.iter.org/fusion-energy/making-it-work

[5] “In a Few Lines,” ITER.org, Nov. 14, 2023. https://www.iter.org/few-lines