Serviceable fusion power is a near-ideal source of effectively limitless clean energy—its high energy density, safety, and sustainability distinguish fusion from any other energy source today. Despite this, the funds required for fusion research and its highly specialized conditions of operation hinder its feasibility in the market (Cowley, 2016). However, as global energy use continues to rise, experts must look towards efficient and environmentally responsible energy sources, making the demand to harness fusion power greater than ever (Smith and Cowley, 2010).
The fusion reaction most commonly used as an energy source on Earth requires two isotopes of hydrogen fusing to form helium and one neutron. The two isotopes are deuterium (D = 2H) and tritium (T = 3H) and the reaction is shown in Equation 1. Initiating this reaction requires both highly dense gas and temperatures over 100 million degrees Celsius to enable the isotopes to overcome mutual electrostatic repulsion and allow the strong nuclear force to act and bind the two isotopes (Smith and Cowley, 2010).
However, due to tritium being unstable with a 12.32 year half-life, fusion reactors generally breed tritium using lithium and the neutron from Equation 1 in the reaction shown in Equation 2 (Cowley, 2016).
These two equations illustrate that for fusion to be successful, immense temperatures and pressures must be created to increase proton kinetic energy for sufficient probability of fusion reactions. At these conditions, matter only exists in plasma, a highly demanding state for efficient energy production (Freidberg, Mangiarotti and Minervini, 2015). In response to this, Russian physicists devised a donut-shaped magnetic confinement device named the tokamak to confine and competently control plasma for energy production (Freidberg, Mangiarotti and Minervini, 2015).
The fusion reactions within the tokamak take place within the torus, a toroidal-shaped steel vacuum chamber surrounded by two configurations of magnetic coils: poloidal and toroidal. Poloidal rings are circular rings around the perimeter of the torus and toroidal rings are larger circular rings that enclose the torus. As a consequence of our fundamental understandings of electromagnetism, we know that the poloidal and toroidal coils each create a high-intensity electric current, which then creates two perpendicular, induced magnetic fields that can safely contain the electrically charged plasma ions shown in Figure 1. As the current moves around the tokamak, a heating effect is produced, which energizes and pressurizes ions to generate collisions (El-zmeter, et al., 2017).
Figure 1: Schematic of a toroidal vacuum chamber. The torus (blue donut) and the electrically charged plasma (gray donut) are depicted. The poloidal (circular white dashed arrow) and toroidal (curved white dashed arrow) magnetic fields are shown. Due to the foundational understanding that electric currents produce perpendicular magnetic fields, these arrows are perpendicular to the physical field coils of a tokamak. Accordingly, the resultant magnetic field is helical (twisting black arrow labelled magnetic field line). Helical movement allows for long-term confinement because in a parallel field, closely orbiting particles can easily collide and fuse (Hazeltine and Prager, 2002).
The tokamak reaction is initiated by deuterium and tritium being fed into the torus at immense atmospheric pressures and temperatures (World Nuclear Association, 2021). These conditions drive the isotopes to fuse together, similar to the environment in the Sun (World Nuclear Association, 2021). The neutrons produced from the fusion reaction (Equation 1) break away from the isotopes and collide with the encompassing structure called the blanket (Buzhinskij and Sements, 1999). The blanket is typically lined with lithium, a heat-resistive element, to allow the chamber to withstand the extreme heat and allow tritium to be bred as shown in Equation 2 (El-zmeter, et al., 2017; Buzhinskij and Sements, 1999). Tokamak reactors generate about 1.5 GW of electricity, enough for more than one million people in a conventional setting (Smith and Cowley, 2010). A simplified scheme of a tokamak is shown in Figure 2.
Figure 2: Schematic of a tokamak. The toroidal field coils (blue rings) and the poloidal field coils (green column) produce perpendicular magnetic fields (blue arrow and circular green arrow, respectively). The outer poloidal field coils (gray rings) shape the plasma positioning. To produce the plasma current, a transformer action in the inner poloidal field coils (green column) is driven and then sustained by the toroidal and poloidal field coils. Deuterium and tritium are fed into the chamber (pink donut) and heated to force their fusion. Although not depicted, the blanket surrounds the reaction chamber and is the location of tritium breeding. The energy released to the blanket is extracted using a cooling circuit and then used to create steam to drive turbines for distribution of electricity to the grid (De Tommasi, 2018).
Despite its high energy density and capacity to produce no greenhouse gases or radioactive waste, the future of fusion remains unclear. The tokamak layout may be proven, but it is incredibly difficult to make this design economically viable. However, with further research and innovation, we can work around these complications and potentially use fusion as a launching pad towards an endless supply of clean energy.
Works Cited:
Buzhinskij, O.I. and Sements, Yu.M., 1999. Thick boron carbide coatings for protection of tokamak first wall and divertor. Fusion Engineering and Design, 45(4), pp.343–360. https://doi.org/10.1016/S0920-3796(99)00007-1.
Cowley, S.C., 2016. The quest for fusion power. Nature Physics, 12(5), pp.384–386. https://doi.org/10.1038/nphys3719.
De Tommasi, G., 2018. Plasma Magnetic Control in Tokamak Devices. Journal of Fusion Energy, 38, pp.406–436. https://doi.org/10.1007/s10894-018-0162-5.
El-zmeter, N., Schmiga, B., Boyd-Weetman, B. and Murphy, A., 2017. Analysis of Tokamak fusion device parameters affecting the efficiency of Tokamak operation. PAM Review Energy Science & Technology, 4, pp.87–102. https://doi.org/10.5130/pamr.v4i0.1444.
Freidberg, J., Mangiarotti, F. and Minervini, J., 2015. Designing a tokamak fusion reactor—How does plasma physics fit in? Physics of Plasmas, 22(7), pp.1–17. https://doi.org/10.1063/1.4923266.
Hazeltine, R.D. and Prager, S.C., 2002. New Physics in Fusion Plasma Confinement. Physics Today, 55(7), pp.30–36. https://doi.org/10.1063/1.1506748.
Smith, C.L. and Cowley, S., 2010. The path to fusion power. Philosophical transactions. Series A, Mathematical, physical, and engineering sciences, 368(1914), pp.1091–1108. https://doi.org/10.1098/rsta.2009.0216.
World Nuclear Association, 2021. Nuclear Fusion Power. [online] Nuclear Fusion Power. Available at: <https://world-nuclear.org/information-library/current-and-future-generation/nuclear-fusion-power.aspx> [Accessed 18 Nov. 2021].
Comments
9 Responses to “A Blast of Clean Energy”
Hi iSci!
While binge-watching YouTube last week, I came upon a series of videos regarding nuclear energy, nuclear disasters, and nuclear bombs. I was really intrigued by a video on nuclear fusion and instantly started reading up on it. I took a moment to look back on first-year where we learned about nuclear fission in RP3, and this prompted me to take a deeper look into the mechanisms behind nuclear fusion, a highly promising solution to our global power concerns. As I researched, I learned a great deal about the principal concepts of nuclear chemistry and the physics behind nuclear fusion. I also got the opportunity to read up on some of the incredible new breakthroughs researchers have seen in this exciting field of energy-related research. I hope you found my blog post engaging, and if you have any feedback or comments, please feel free to list them below. Thank you for all your help and I hope you have a great day!
Hi Rith,
I enjoyed reading your blog post. I’ve heard about fusion energy but never completely understood how it works, so I found your post very interesting. I have a few small suggestions that may help.
1. The last sentence of your second paragraph is a little hard to follow. Instead of “Initiating this reaction requires both highly heated and dense gas over 100 million degrees Celsius….”, consider changing it to something like “Initiating this reaction requires both highly dense gas and temperatures of over 100 million degrees Celsius …”.
2. If your word count permits, consider going into more depth on how the scientists would superheat and pressurize the gasses that are involved in the reaction. I feel like it might give more insight on why this energy source is so difficult and expensive to maintain.
3. This is minor but try to keep your in-text figure references consistent if possible. For example, when referencing Figure 1, try to add it into a sentence rather than in parentheses.
Overall, I found your post very interesting and I learned a lot while reading it. I can’t wait to read the final copy.
Luc
Hi Luc,
Thank you so much for your comments. I implemented them all into my final draft.
Rith
Hi Rith,
This was a super interesting post to read! I liked your figures, they helped me visualize what you were talking about really well. Here are a few suggestions from me:
– I think it might be beneficial if you expand a bit more about why this is sustainable potential energy source. Perhaps in your conclusion you can explain why the process does not produce radioactive waste and why it is so energy dense. This links the scientific process you are describing to its outcomes more clearly than just stating as a fact that it is energy dense and it does not produce radioactive waste.
– I also agree with the above comment that it would be interesting to learn more about how the scientists would superheat and pressurize the gasses if you have the space
– It also might be interesting to include how expensive it might be to build a tokamak if that information is available or some numbers on how expensive fusion is in general but that is not completely necessary
Hope this is helpful, happy editing!
– Adrianna
Hi Adrianna,
Thank you very much for all of your comments, they gave me a lot to think about. I addressed your second point in the final sentence of my fifth paragraph. For your first point, as I mentioned in paragraph three, tritium can be produced from a reaction with lithium in the reactor, and deuterium is readily available on Earth. For your last point, I could not add this because of word count restrictions, but tokamak reactors typically cost upwards of $10 billion dollars, but the overall cost is highly dependent on the entire scale of the project. Thank you for your help!
Rith
Hi Rith,
I think your blog post was very well done. Notably, I thought your figures were great additions to the writing and that your tone was appropriate. However, I have some suggestions you may wish to consider:
1) In certain paragraphs, like paragraph two, you do not need multiple in-text citations of the same source if the whole paragraph is from one source. For example, in paragraph two, you can delete all “(Smith and Cowley, 2010)” references except for keeping the one at the end.
2) While this is personal preference, it may be easier to find equations if you write “Equation #” before the equation instead of after.
3) In the first sentence of paragraph four, I would change “and increased” to “thus increasing the”.
Overall, this post was very enjoyable and well-written. I look forward to reading your final copy.
Happy editing,
Tushar
Hi Tushar,
Thank you for taking the time to read and comment on my post. I implemented the first two changes into my final copy. I also modified the specific sentence you mentioned in your third point so that it would make more sense. All of your comments were great.
Rith
Hi Rith,
Really well written blog post, I did not know fusion power was so interesting! I do have some suggestions though:
– I liked your equations and I feel like it would be great if you could further explain them, potentially by treating the equation as a figure and then providing a figure caption
– The last sentence in your first paragraph seems to be a little long and run-on. Try to see if you can rewrite it, such as by saying “However, as global energy use continues to rise, experts must look towards efficient, environmentally responsible energy sources. As a consequence the demand to harness viable fusion power becomes greater than ever.”
– I think you might be able to make your first figure a little bit bigger so the smaller text is visible, which should not be a hard fix
Other than that, I feel you did a great job and I wish you luck in edits!
– Yash
Hi Yash,
You made some really excellent points here, so thank you for the unique insight. For your second point, I replaced a comma with an “and” so the sentence would be less run-on. Your third point was spot-on so I made Figure 1 larger. For your first point, I could not add more about the equations because I’ve reached the word cap, but those chemical equations are not very complicated. Equation 1 is just the fusion reaction in the reactor and Equation 2 is how tritium is made. Both these equations work hand-in-hand in the fusion reactor to produce energy. I hope that helps, but thanks again for your help!
Rith