Current Challenges of Nuclear Fusion

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Jonathan Seyoum is the CEO of FieldClerk.com, an AI data parsing software company, and is currently based in Denver, CO.  Jonathan holds a Bachelor of Science in Mechanical Engineering (BSME) from Rice University and has experience in the construction and project management software industry. Before creating his first company, Jonathan had held positions in specialized capital projects companies, having worked on midstream oil and gas construction projects and private infrastructure, where he identified the key limitations of software in the construction industry that served as his launchpad for his first company.  A serial entrepreneur, Jonathan began his first side business detailing and customizing sneakers, which laid the foundation for his entrepreneurial endeavors. Jonathan holds many interests outside of engineering, including but not limited to finance, software, AI, and construction. It is a distinct pleasure to call Jonathan my lifelong friend and forever college roommate, and his article below will exhibit his expertise and passion for the work he does professionally and outside of work. 

Articles in discussion:

• Nuclear fusion – Wikipedia

• DOE Explains… Fusion Reactions – U.S. Department of Energy

• Nuclear Fusion Explained – World Economic Forum

• Nuclear Fusion Power – World Nuclear Association

• Releasing the Potential of Fusion Energy – Clean Air Task Force

• Fusion Reactors: Not What They’re Cracked Up to Be – Bulletin of the Atomic Scientists

• Nuclear Fusion: The True, the False, and the Uncertain – Polytechnique Insights

• Global Fusion Industry Report 2024 – Fusion Industry Association

• Conditions for Fusion Ignition – Max Planck Institute for Plasma Physics

• Nuclear Fusion Breakthrough Raises Hope for Limitless Clean Energy – Mewburn Ellis

Introduction

Nuclear fusion is the process where two nuclei combine to form one heavier nucleus, typically releasing energy in the process. Since the combined nucleus has a smaller mass than that of the two initial nuclei, the excess mass is released as energy. The excess mass stems from the difference in nuclear binding energies between the nuclei before and after the process. This process is the same process that powers the sun and stars.  

For the two nuclei to combine, the matter must reach a state of plasma: a gaseous state with positive ions and free electrons that exhibit unique properties. Fusion occurs at extremely high temperatures, requiring temperatures exceeding 100 million degrees Celsius. While plasma can form at lower temperatures, such as 10,000 degrees Celsius, the temperatures needed to fuse the nuclei are much higher. These temperatures also fluctuate depending on the gas used to start the reaction. Deuterium and tritium, for example, are known for allowing fusion to take place at lower temperatures than other elements, and, hence, are the most common fuels in laboratory fusion reactions.

Figure 1: Deuterium (D) fusing with Tritium (T) to produce a helium nucleus (He), neutron, and excess energy

Importance of Nuclear Fusion

The importance of nuclear energy becomes clear when its potential impacts are considered. For example, fusion can generate four times as much energy as fission and four million times as much as coal and oil on a per kilogram of fuel basis. This efficiency means fusion can now become a more renewable energy source than our current options. However, when a closer look is taken at nuclear fusion, the advantages grow exponentially. 

As noted in the introduction, the main characteristic of fusion is its ability to release more energy than it takes in. If this released energy is harnessed efficiently, fusion will provide a source of energy that is practically inexhaustible. With abundant resources of deuterium and tritium, the most commonly used nuclei in the process, running out of an energy source would be a concern of the past. Furthermore, this process releases no carbon emissions of greenhouse gasses, providing an environmentally friendly way of producing energy. It also produces minimal, shorter-lasting radioactive waste, as opposed to nuclear fission and other energy sources, making it an extremely valuable potential energy source for the world.

Current State of Fusion

Laboratory thermonuclear fusion first took place in 1958 in the Los Alamos National Laboratory. From this point on, the focus has been on extracting and utilizing the benefits of this method of energy production. In 2022, a team at Lawrence Livermore National Laboratory made history by achieving the first gain of energy from a fusion reaction. During the reaction, 2.05 MJ of energy was added to the nuclei using lasers, and 3.05 MJ was released during the fusion of the two. The reaction used deuterium-tritium fuels due to the lower temperatures required for fusion, and current research continues to focus on these fuels for future experiments.

Figure 2: A photo of the inside of the Lawrence Livermore National Laboratory fusion reactor

Currently, governments and private entities all over the world have been working together to further the efficiency and usability of fusion. This focus on fusion has greatly increased over the past years, and funding has also significantly grown after the 2022 experiments. The image below shows the growth of private companies and private investments in fusion from 2000 until 2021.

Figure 3: Depiction of the growth of private companies and investments in fusion research from 2001 until 2021

While this growth is immense, since 2021, the number of private companies focused on nuclear fusion research has grown to 43 as of 2024. The amount of private investments has also grown to $7.1 billion. The public funding and research focus has also scaled similarly, leading to a huge focus on this process that is said to be the solution to our energy needs. This increased funding and focus on advancing the research and capabilities of thermonuclear fusion are changes that are needed to push the feasibility and viability of fusion as a main energy source.  

General Challenges

While the potential of nuclear fusion is great, considering all the positives and the virtually unending renewable energy source, nuclear fusion is still a long way away from being the energy source it shows promise to be. When closely analyzed, there are many gaps still left between the current technologies and those required to harness the excess energy. While the 2022 experiment and following similar experiments achieved a positive energy output, the energy output is nowhere near enough to power the facility or even the laser that was used to power the target. NIF scientists estimate that it will take 100 times the net energy gain to power the laser alone, mainly due to the energy that is lost to the surrounding environment, which never reaches the target. Similar difficulties with the process, materials, costs, and more add up making it difficult to attain the allured benefits of fusion. Some examples of the difficulties include:

 Igniting the Plasma

As stated earlier, fusion needs temperatures above 100 million degrees Celsius to take place. While the sun can use its strong gravitational pull to induce this ignition, and the whole fusion process, here on Earth this becomes much more difficult. The 2022 experiment, for example, required 192 of the strongest lasers to heat the gasses enough to ignite and start the fusion process. Not only does it require temperatures 6 times those of the center of the sun, but the ignition also requires 10^14 particles per cm^3. When combined, these two characteristics are significantly difficult to achieve, hence the 60-year gap between the first fusion experiment to the first “net-positive” experiment in 2022.

Sustaining the Plasma

Even harder than igniting the plasma, the characteristics listed above must be maintained for a period long enough to allow fusion to take place. The plasma must have an energy confinement time of 2 seconds, meaning the energy added to the plasma must not escape for at least two seconds. While this is being done, the plasma must be confined, typically through magnetic fields or lasers. Keeping the plasma at these required values for a long enough duration was the second challenge scientists were met with. Controlling the plasma becomes harder as more energy is added, making each step closer to fusion a harder one. Furthermore, instabilities occur within the plasma, destroying the plasma formation and potentially the equipment that holds it. These instabilities are very unpredictable, have limited controllability and prevention, and prevent the plasma from sustaining long enough for fusion to take place

Figure 4: A depiction of the plasma inside a nuclear fusion reactor

Harnessing the Energy

 The fusion reactions output energy in the form of energy neutron streams with 80% of the deuterium-tritium reactions and 20% of deuterium-deuterium reactions. These neutron streams are those that sustain the neutrons in the galaxy but are not ideal for electrical energy. The conversion from this energy output to electricity is a difficult one, meaning that net-positive gains would still not be valuable until this conversion can efficiently take place. The neutron streams also lead to a variety of radioactive waste that can prove harmful to the equipment or environment if not properly controlled. This waste can be hard to control, at times going through concrete and even steel materials, posing a threat to the environment if not handled properly. While the waste is not as radioactive as fission waste on a per-mass basis, the mass of fusion waste is much larger than that of fission, and its volume is equivalent, leading to increased handling challenges. 

Along with these difficulties, the high cost of experimentation, scaling challenges with any successful experiments, equipment challenges, laser heat loss, and more, means that the jump from net-positive to usable, overall net-positive nuclear fusion is a hard one to make. 

Future Outlook 

Nuclear fusion research has come a long way but also has many critical aspects that have not yet been solved. The focus on increasing funding, focus, and research in this field is one that is critical both for fusion reactors and the world. As more innovation takes place to solve the equipment challenges, and new research breakthroughs occur to improve the process, fusion will become a more and more achievable source of energy. Many challenges are yet to be overcome, and while the feasibility might still be in question, the recent developments seem to be promising. Each advancement will take humanity one step closer to harnessing the sustainable clean energy fusion offers.

Disclaimer: The reflections shared here are the contributor's technical and analytical perspectives. They are not definitive statements of fact or policy positions. I welcome thoughtful discussion; feel free to contact me or them if you’d like to explore these ideas further.