An Introduction to Fusion Energy

Figure 1: A photo of the construction of ITER from May 2022 [4]

Fusion energy has been powering the earth for billions of years. Without the massive ball of plasma in our solar system, the earth would have never had the heat necessary to sustain life on our planet. If the sun is producing so much power through the fusion of lighter nuclei into heavier ones, what’s stopping us?

The solution isn’t so simple, what we call thermal energy can more accurately be describe as the kinetic energy of particles that make up matter. To attain fusion, particles need to be extremely hot to overcome the coulomb repulsion of the positively charged tritium and deuterium ions, but this means they are now moving extremely fast [1]. In effect, containing these particles becomes difficult, and where the sun has a huge gravitational pull keeping the plasma together, human-made systems struggle to contain this high energy plasma. In fact, containing plasma is currently the largest obstacle in human-made fusion reactors [2]. This has led researchers to investigate more innovative solutions to this problem, the most common type of confinement being researched is magnetic confinement which uses many magnetic coils to confine plasma in the shape of a torus [3]. Tokamaks have tried to achieve this by inducing plasma currents to sustain the plasma but encounter several instabilities that would are too complex to describe in a single blog post. However, years of research and progress have diminished the effects of the instabilities or even gotten rid of some altogether [2]. This has progressed to the point that an international effort known as the International Thermonuclear Experimental Reactor (ITER) has been in the works for years [3]. Slated to now begin experiments in 2025, this reactor should be able to produce 500MW of thermal energy output with less than 50MW of plasma heating power input [3].

ITER is not the only reactor which researchers, private companies, and government agencies are hopeful about. Similar reactor designs like the spherical tokamak and the rotamak are also being researched as potential fusion reactors [2]. More notably, in recent years there has been a lot of interest in stellarators which simplify plasma control, have greater design flexibility, and require less injected power to sustain plasma [5]. This however comes at the expense of increased complexity in design and much greater costs to build.

Figure 2: Conventional (left) and optimized (right) stellarators both use complex electromagnetic coils to confine plasmas using three-dimensional magnetic fields in the shape of a torus without relying on induced plasma currents to sustain the plasma [5].

Despite the slow progress and many hiccups along the way caused by new obstacles in an ever-growing field of research, fusion energy remains one of the most promising clean generation methods that could power the world for centuries to come.

References

[1]          University of Calgary, “Nuclear fusion – Energy Education,” Energy Education. https://energyeducation.ca/encyclopedia/Nuclear_fusion (accessed Nov. 06, 2022).

[2]          M. Tuszewski, “Field reversed configurations,” Nucl. Fusion, vol. 28, no. 11, pp. 2033–2092, Nov. 1988, doi: 10.1088/0029-5515/28/11/008.

[3]          World Nuclear Association, “Nuclear Fusion Power.” https://world-nuclear.org/information-library/current-and-future-generation/nuclear-fusion-power.aspx

[4]          “Most complex lift to date completed at ITER : New Nuclear – World Nuclear News.” https://www.world-nuclear-news.org/Articles/Most-complex-lift-to-date-completed-at-ITER (accessed Nov. 06, 2022).

[5]          “DOE Explains…Stellarators,” Energy.gov. https://www.energy.gov/science/doe-explainsstellarators (accessed Nov. 06, 2022).

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