video Episode 2.3

Building stars on Earth: the potential of nuclear fusion

Energy from nuclear fusion has the potential to cleanly and safely power the world.
But, when do fusion experts expect this to happen? What technical challenges must be overcome before we can power our homes using fusion energy? Which technologies are leading the pack and who is developing them?
Climate Now host Dr. Ozak Esu dives into the science behind nuclear fusion and its difficulties in this episode featuring Sir Steven Cowley, director of the Princeton Plasma Physics Laboratory, and Dr. Aneeqa Khan, Research Fellow in Nuclear Fusion at The University of Manchester.

Running Time: 14 mins

Date: 09.03.2021

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Aneeqa Khan
Research Fellow in Nuclear Fusion


Aneeqa Khan

Research Fellow in Nuclear Fusion

Aneeqa Khan is a Research Fellow in Nuclear Fusion in the Department of Mechanical, Aerospace, and Civil Engineering (MACE) at the University of Manchester. Her research is focused on testing materials and components for nuclear fusion applications. She previously was a postdoctoral scholar at the international nuclear fusion project ITER.

Steven Cowley
Director of the Princeton Plasma Physics Laboratory


Steven Cowley

Director of the Princeton Plasma Physics Laboratory

Sir Steven Cowley is a theoretical physicist and international authority on fusion energy. He is the Director of the Princeton Plasma Physics Laboratory (PPPL), and a Princeton professor of astrophysical sciences. He was most recently president of Corpus Christi College and professor of physics at the University of Oxford. Cowley previously was chief executive officer of the United Kingdom Atomic Energy Authority (UKAEA) and head of the Culham Centre for Fusion Energy.

Hosted By:

Ozak Esu
Climate Now Host


Ozak Esu

Climate Now Host

Dr. Ozak Esu is a Chartered Engineer and a STEM Education Ambassador, working within Construction and the Built Environment industry. Inspired by her lived experience of energy poverty growing up in Nigeria, she chose to pursue a career in Electronics and Electrical Engineering, receiving her bachelor’s degree from Loughborough University, UK. She graduated with a first-class and was awarded a scholarship to advance to her PhD. in wind energy. By participating in Climate Now, Ozak is keen to contribute her knowledge of technologies, her experience of the challenges faced, and to be a voice for regions often underrepresented, in the conversations about climate change and a sustainable energy future.

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Video Episode 2.3 Transcript

At its core, nuclear energy is a technology that involves extracting energy from atoms. The well-known and most developed way to do this is a process known as nuclear fission, where atoms are split apart. And the energy released is used to power portions of the power grid. But in fact, there is another form of nuclear energy scientists are developing that is based on how our sun and every other star in the universe creates and radiates energy. This is through a process called nuclear fusion. Nuclear fusion is when elements like hydrogen are exposed to such extreme temperatures and pressures that they fuse together and create other elements. It is this reaction alone that is the basis for the energy that sustains life on earth.


Today, scientists are attempting to replicate nuclear fusion in order to create a carbon-free and virtually limitless supply of energy. In this episode of Climate Now, we are going to explain how this is even possible, who’s working on this technology, and how soon we might be able to power our everyday lives using nuclear fusion energy. To explain to us how nuclear fusion works, we spoke with theoretical physicist, Dr. Steven Cowley, director of Princeton Plasma Physics Laboratory.


Sir Steven Cowley:

Inside stars, what stars are doing, they’re taking hydrogen and they’re putting it together and they’re making helium. And they do this by a process called nuclear fusion. And then they take helium and they put it together and they make carbon. And then they add onto that. And all the elements that are in your body were created by this process of fusion, which is sticking together, small nuclei, fusing them and making bigger nuclei out of it. And when you do that, you release lots of energy, a tremendous amount of energy each time. And that’s why the sun is hot, right, why the stars shine. And so fusion in some sense is the thing that makes life happen.



But how do we recreate the energy of the sun here on earth? And in a way that’s not quite so big or hot? Currently, there are two ways to confine a nuclear fusion reaction. The first is through magnetic confinement. This is where two isotopes of hydrogen, deuterium and tritium, are heated to more than 150 million degrees Celsius. At this temperature, the hydrogen isotopes disintegrate into a sea of electrons and nuclei, otherwise known as plasma. As hydrogen nuclei fuse together to create helium, immense amounts of energy are released. Due to the fact that there is no known material that can withstand such extreme temperatures, the plasma is contained and controlled via a magnetic field.


The second way to confine nuclear fusion is through inertial confinement, where energy is generated through a series of pulses from superpowered lasers, capable of fusing atoms together. In this process, fuel pellets containing 150 milligrams of deuterium and tritium are exposed to a massive laser pulse of energy, which induces an explosion so intense that a fusion reaction is ignited in the core of the pellet and then spreads throughout. While it has yet to be demonstrated, the heat generated through nuclear fusion is then theoretically captured to produce steam, which would drive steam turbines, and thus produce electricity.


The most successful and developed fusion vessels to date are the magnetic confinement reactors. In this category, there are two designs that dominate: the Tokamak and the Stellarator. We spoke with Dr. Aneeqa Kahn materials engineer, and nuclear fusion research fellow at the University of Manchester about the two reactor types.

Aneeqa Khan:

So there’s something called a Tokamak, which is kind of a donut shaped device, where you have magnets that create, in the poloidal and toroidal directions going this way and this way, so that you can confine your plasma with a magnetic field. And then also stellarators, which are really crazy looking machines, which I highly recommend everyone looks up a picture of a stellarator because the engineering on that is just phenomenal. They’ve got lots of twists and turns and very high tolerances and yeah, they’re quite tricky to make. On the current pathway to fusion power, I would say the Tokamak is the most favored device and the one that’s being pursued by the most people.


To emphasize the wonder of it Tokamak reactor. This vessel is designed to withstand temperatures around 150 million degrees Celsius. That’s 10 times hotter than the center of the sun! The reason why we need to produce this much heat is because it is the only way to reach the physical conditions required to fuse atoms together without actually recreating the sun. What’s more is that in order to maximize the thermal efficiency of the Tokamak, the walls of the reactors are cooled with liquid helium to a temperature that is near absolute zero. While hosting such extreme temperatures in one space may seem unbelievably or even outright dangerous. It’s actually not as risky as one might think.


Sir Steven Cowley:

This is the nice thing about having something where you put it in as a gas, it becomes a plasma and you burn it. You put some more in it. It’s like an internal combustion engine. You know, you don’t have the cylinder inside your fuel tank in a car, right? You take the fuel down a pipe and you put a little bit into the cylinder at any one time, and then there’s a little explosion, but that explosion is not enough to break anything, right? Each time you fire that spark plug, there’s a little explosion.


Creating that little explosion, however, is one of the most challenging steps yet. Today there is a project on the way to construct the world’s largest Tokamak, which will help physicists study nuclear fusion in new and innovative ways. This Tokamak is being built in the south of France and is known as ITER, originally short for International Thermonuclear Experimental Reactor. ITER is a joint effort between China, the EU, India, Japan, Korea, Russia, and the US, and its goal is to eventually produce 500 megawatts of fusion power from 50 megawatts of heating.


Sir Steven Cowley

That is supposed to get to the point where you don’t have to put any energy into the plasma because it’s self heating, because the fusion heats the plasma and you’ve lit the fire, and you can take the match away. And that’ll be amazing because then, you know, you can turn off all external heating sources and the thing will just burn like a star. That will be one of those historic moments in science.


If ITER can reach this milestone, it will prove that nuclear fusion can be a net source of energy. However, ITER will not be designed to supply energy to the power grid. Other demonstration fusion power plants also known as demos will be needed to exhibit the commercial potential of fusion energy. At the writing of this video, ITER is still in the construction phase, where components are being built and shipped in from all over the world. If all goes, according to plan this $20 billion vessel will begin running its first experiments by 2025.


Another fusion reactor vessel that’s worth mentioning is a German Wendelstein 7-X Stellarator, which confines plasma using 50 non-planar superconducting magnetic coils. As a result of this magnetic field geometry, the stellarater does not require an electrical current to operate, which is a major advantage over the tokamaks since we want to maximize on the amount of energy we get out versus the amount we need to put in. TheWendelstein has been in operation since 2015, and in 2018 demonstrated a continuous plasma reaction for up to 30 minutes. However, the complex design of the Wendelstein has limited its development leading physicists to favor the Tokamak design.


Going beyond tokamaks and stellarators, there are also other types of vessels such as the reactor found at the National Ignition Facility in Livermore, California. This reactor uses one of the strongest lasers in the world to attempt fusion reactions via international confinement. On August 8th, 2021, they achieved 1.3 megajoules of fusion yield while injecting 1.9 megajoules of laser energy, an advancement from their previous record of 0.17 megajoules.

Private companies like General Fusion, Tri Alpha Energy and Commonwealth Fusion Systems are also building nuclear fusion, reactors, and competing to be the first to produce sustainable fusion energy. General Fusion, who is backed by billionaire Jeff Bezos, claims that by 2030, it will be possible to use nuclear fusion, energy to power our homes. But these ambitious goals are disputed by scientists who say there is still so much. We don’t know about sustaining a nuclear fusion reaction, and it would be unrealistic to promote these goals.



So you might be wondering, is it safe to create the energy of the sun and stars here on earth? According to the experts the fusion process is inherently safe.

Aneeqa Khan:

So one of the good things about fusion is that it is really difficult to do so. It means that that reaction will stop if those conditions are not met, the plasma will just vanish, disappear. So, you know, there’s not really a risk of having like a huge meltdown or anything like that with fusion.


That’s right, due to the fundamental differences in the physics and technology of fusion reactions, there is no risk of an event like Chernobyl or Fukushima. While tritium is a radioactive form of hydrogen, its half-life is 12.3 years, and the amounts that will be used at ITER will be less than four grams at any given time. Additionally, the tritium stays within the reaction and is not released, nor is it a waste product. Even in an absolute worst case scenario, where tritium is leaked into the environment, human exposure to radiation would be at most 1000 times less than the natural background radiation. Most importantly, nuclear fusion does not produce long-lived or high level radioactive waste. The byproducts of a fusion reaction are helium, an inert gas, and high energy neutrons. Since neutrons are unaffected by magnetic fields, they escape the plasma and interact with the walls of the reactor, making the structural materials radioactive, however, physicists carefully select materials that reduce radiation intensity. Most of the radio isotopes produced from nuclear fusion have a half-life of less than 10 years, meaning that within 100 years, these radioactive materials will have diminished to safe levels. Nuclear waste from fusion is therefore much safer and shorter-lived spent uranium fuel from nuclear fission.



In spite of fusion’s potential to provide safe and clean energy, all projects that involve testing and developing fusion energy are still in the experimental phase. So estimates relating to how much fusion energy will cost. And if it will be competitive are mostly theoretical, while scientists anticipate that costs will be largely driven by operational and infrastructure names. One study predicts that nuclear fusion has the potential to become the cheapest and cleanest source of energy by the end of the century, given its key advantages such as its inherent safety and negligible environmental impact.



The EU has developed a roadmap towards fusion electricity. And in that roadmap, ITER plays a central role. Scientists anticipate that by 2035 ITER will be able to prove that it is possible to produce sustainable nuclear energy. However, it won’t be until after the 2050s, when DEMO plants demonstrate the ability to introduce fusion energy into the power grid. Most experts agree that we won’t see full commercialization until the mid or later part of the century.


While nuclear fusion will not be a near term answer to climate change. It will be important to prepare for the day when we can rely on this technology as a safe and carbon-free alternative to fossil fuels. Even more importantly, development of renewable energy must continue to focus on what is already available now: fission energy, solar and wind power, as well as geothermal and hydroelectric energy. These technologies will be our answer until the day when we can harness the power of the sun right here on earth.

For a deeper dive into this topic, check out our full-length podcast with Dr. Steven Cowley and Dr. Aneeqa Khan, where we dig deeper into the ins and outs of nuclear fusion technology. To sign up for new releases and more, visit climatenow.com. Thanks and see you next time!



  1. 1:56 Charley, S. (2012, January 12). How to Make an Element. PBS. https://www.pbs.org/wgbh/nova/article/make-an-element/ 
  2. 2:45, 3:10, 7:22  Video Courtesy of ITER
  3. 2:47, 5:24  Machine. ITER. (n.d.). https://www.iter.org/mach 
  4. 2:35, 2:47, 3:13 Breeze, P. (2019) Power Generation Technologies (Third Edition) Chapter 17 – Nuclear Power https://doi.org/10.1016/B978-0-08-102631-1.00017-1
  5. 3:03 Capturing the energy. ITER. (n.d.). https://www.iter.org/sci/MakingitWork 
  6. 3:29 Image from Lawrence Livermore National Laboratory July/August 1999 Science & Technology Review publication.
  7. 3:44 Lawrence Livermore National Lab. How NIFWorks. https://lasers.llnl.gov/about/how-nif-works
  8. 3:58, 12:56 Entler, S., Horacek, J., Dlouhy, T., & Dostal, V. (2018, March 26). Approximation of the economy of fusion energy. Energy. https://www.sciencedirect.com/science/article/pii/S0360544218305395 
  9. 4:10 Office of Nuclear Energy. (2021, April 1). Fission and Fusion: What is the Difference? Energy.gov. https://www.energy.gov/ne/articles/fission-and-fusion-what-difference.
  10. 4:23 Image of Tokamak: projet KSTAR (Daejeon, Corée du Sud) from Michel Maccagnan (8 Aug 2007) licensed under the Creative Commons Attribution-Share Alike
  11. 4:23 Image of C , D-prime view of HSX (Helically Symmetric eXperiment) stellarator (2003)
  12. 5:45 Carnot’s principle – Carnot’s rule. Nuclear Power. (2018, April 25). https://www.nuclear-power.com/nuclear-engineering/thermodynamics/laws-of-thermodynamics/second-law-of-thermodynamics/carnots-principle-carnots-rule/.
  13. 5:49 Wong, C. P. C., Baxi, C. B., Hamilton, C. J., Schleicher, R. W., & Streckert, H. (1994). HELIUM-COOLING IN FUSION POWER PLANTS. International Atomic Energy Agency. https://www.researchgate.net/profile/Clement-Wong-3/publication/255190791_Helium-cooling_in_fusion_power_plants/links/54d8d06a0cf24647581c302f/Helium-cooling-in-fusion-power-plants.pdf
  14. 7:00, 8:36 Frequently Asked Questions. ITER. (n.d.). https://www.iter.org/faq#collapsible_3 
  15. 8:29 Non-planar coil for National Compact Stellarator Experiment (NCSX) from Princeton Plasma Physics Laboratory (2008), US Department of Energy.
  16. 8:36 Picot, W. (2021, May 13). ITER: The World’s Largest Fusion Experiment. IAEA. https://www.iaea.org/fusion-energy/iter-the-worlds-largest-fusion-experiment 
  17. 8:42 German Wendelstein 7-X Stellerator, Max-Planck-Institut für Plasmaphysik, Tino Schulz – Public Relations Department, https://www.ipp.mpg.de/w7x
  18. 9:15 Wendelstein 7-X. Max-Planck-Institut für Plasmaphysik. (n.d.). https://www.ipp.mpg.de/w7x 
  19. 9:24  K.H. (1970, November 12). Fusion world: What’s next for the stellarator? ITER. https://www.iter.org/newsline/-/3169 
  20. 9:33 Lawrence Livermore National Lab – CC BY-SA 3.0
  21. 9:35 Lawrence Livermore National Lab. “National Ignition Facility experiment puts researchers at threshold of fusion ignition” (8 Aug 2021) https://www.llnl.gov/news/national-ignition-facility-experiment-puts-researchers-threshold-fusion-ignition
  22. 10:13 General Fusion @GeneralFusion. “We are excited to build….” Twitter, (2021, June 18), https://twitter.com/GeneralFusion/status/1405971579243089920
  23. 10:13 General Fusion’s Team, Investors and Research Partners. General Fusion. (2021, June 16). https://generalfusion.com/management-research-team-investors/#investors 
  24. 10:37, 11:03 Safety and Environment. ITER. (n.d.). https://www.iter.org/mach/safety 
  25. 10:37 Doshi, B., & Reddy, D. C. (2017, March 1). Safety and Environment aspects of Tokamak- type Fusion Power Reactor- An Overview. Journal of Physics: Conference Series.  https://iopscience.iop.org/article/10.1088/1742-6596/823/1/012044 
  26. 11:03, 12:05 Jordan, K. C., Blanke, B. C., & Dudley, W. A. (2003, May 20). Half-life of tritium. Journal of Inorganic and Nuclear Chemistry. https://www.sciencedirect.com/science/article/abs/pii/0022190267802653 
  27. 12:09 Khan, Aneeqa personal communication, July 08, 2021
  28. 12:12 Image of Common Spent Nuclear Fuel pool at Fukushima Daiichi Nuclear Power Station from IAEA Imagebank (27 November 2013) licensed under Creative Commons Attribution-Share Alike.
  29. 12:13 Barrels of waste from ShinRyu Forgers (31 October 2014) licensed under Creative Commons Attribution-Share Alike
  30. 12:40, 13:00, 13:22 Donné , A. J. H. (2019, February 4). The European roadmap towards fusion electricity. Philosophical Transactions of the Royal Society A. https://royalsocietypublishing.org/doi/10.1098/rsta.2017.0432 


Further Reading

  1. White Paper – Preliminary Options for a Regulatory Framework for Fusion Energy Systems. U.S. Nuclear Regulatory Commission. (2021, April). https://www.nrc.gov/docs/ML2111/ML21118A081.pdf.
  2. Roma, A. C., & Desai, S. S. (2020, February). The Regulation of Fusion – A Practical and Innovation-Friendly Approach. Hogan Lovells. https://www.hoganlovells.com/~/media/hogan-lovells/pdf/2020-pdfs/2020_02_14_hogan_lovells_the_regulation_of_fusion_a-practical.pdf?la=en.
  3. GOV.UK. (2021, June 1). Regulatory Horizons Council Report on Fusion Energy. https://www.gov.uk/government/publications/regulatory-horizons-council-report-on-fusion-energy-regulation.
  4. Cormier, K., & de Vos, M. (2020, October 6). CNSC Regulatory Approach for Fusion Related Activities. U.S. Department of Energy Office of Science. https://science.osti.gov/-/media/fes/pdf/2020/NRC-Public-Forum/AS1_B.pdf?la=en&hash=087484700439C8F09E23F4B409E88BBE9D6701DA.
  5. Nuclear Safety and Control Act (S.C. 1997, c. 9). Retrieved from the Justice Laws website: https://laws-lois.justice.gc.ca/eng/acts/n-28.3/page-1.html


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