Fusion power

Fusion power is an experimental energy source that aims to replicate the type of nuclear fusion that replicates the nuclear processes in stars such as the sun. It involves controlled collisions between atom- or isotope-based fuel sources, which then combine to form new particles with heavier nuclei. This process releases large amounts of energy, which can then be amassed, stored, and used to generate electricity. Scientists and researchers widely consider fusion power a desirable technological advancement potentially capable of providing a sustainable, mass-scale solution to the world’s soaring electricity demands.

As an energy source, fusion power would offer considerable benefits. According to the ITER Organization, a major international nuclear fusion research group, fusion power offers a potential energy solution that is much more efficient than conventional techniques. It draws on abundant, readily available, and practically unlimited raw materials without emitting greenhouse gases or creating unstable, long-lived radioactive waste. Modern fusion reactors also pose no risk of meltdown, giving fusion power a favorable safety profile relative to conventional nuclear power.

Optimistic projections anticipate that fusion power technologies could be available by the 2030s. However, researchers and engineers must first overcome several practical challenges currently inhibiting its commercial viability.

Background

Physicists often describe the structure of atoms as being akin to tiny solar systems: The core component of an atom is its nucleus, which occupies the center of the atomic structure just as a star forms in the center of a solar system. Negatively charged particles called electrons orbit the nucleus, just as planets orbit a star. Atomic nuclei contain dense concentrations of positively charged particles called protons and uncharged particles called neutrons. Protons and neutrons are bound together in nuclei by the combined action of a strong force and an electromagnetic force. Physicists describe this combined force as the strongest force in nature.

Two processes that interact with these binding atomic nuclear forces can be used to trigger physical and chemical changes that release large amounts of energy. These processes are known as fission and fusion. In nuclear fission, one large atom is split into two or more smaller particles, and the energy released by this process is collected and used to generate electricity. Nuclear fusion takes the opposite approach: it merges two or more smaller atoms into a single larger particle, which also releases energy capable of serving as an electricity source.

Conventional approaches to nuclear power generation use fission to harness the energy released by splitting one atom into multiple smaller particles. Uranium is the preferred element for generating fission power. It is the heaviest element found in nature, with ninety-two protons in its nucleus. Because uranium nuclei are so large and heavy, the forces that hold them together are weak compared to other elements. Their size and density also mean that they release relatively large quantities of energy when fission occurs. In fission power plants, technicians bombard uranium atoms with neutrons, weakening and ultimately wearing down the forces that bind their nuclei. When the bond breaks, the uranium atom ejects the neutrons in its nucleus. These neutrons then crash into adjacent atoms, creating a kind of chain reaction that releases large amounts of energy. This energy is directed into water reservoirs, heating the water to approximately 270 degrees Celsius (about 520 degrees Fahrenheit) and vaporizing it. The resultant steam exerts pressure on connected turbine systems, causing the turbines to spin and generate electricity. This electricity can then be distributed across power grids.

Fission power offers considerable benefits. It produces energy thousands of times more efficiently than fossil fuel combustion without producing any direct carbon dioxide emissions, which have strong links to global warming and climate change. It is also reliable, and relatively inexpensive after initial startup costs. However, fission power also poses some problems, some of which have potentially disastrous consequences. Uranium mining operations take a heavy toll on the environment, and fission produces radioactive waste with a long half-life. This waste must be safely stored, as it can cause radiation sickness, cancer, and other severe health problems in people who have been exposed to it. Accidents such as the 1986 nuclear meltdown and explosion at a Soviet nuclear power plant in Chernobyl, Ukraine, remain a constant threat, as they are capable of contaminating wide, densely populated regions and endangering the health and lives of millions of people. The 1986 Chernobyl disaster, and other incidents such as the 1979 partial nuclear meltdown at Three Mile Island, Pennsylvania, and the 2011 Fukushima Daiichi power plant accident in Japan, also had a negative impact on the public perception of nuclear fission energy. Fusion power has been proposed as a safer, cleaner alterative to nuclear fission, as it offers a superior security profile with far fewer environmental impacts.

Brief History

Nuclear energy became a topic of intense scientific focus during the 1930s and early 1940s, when World War II (1939–1945) triggered a high-stakes rivalry among opposing Allied and Axis powers. Initially used to create highly destructive weapons, nuclear technology was commercialized as an energy source during the early postwar era. Scientists began experimenting with nuclear fusion reactions during the 1940s and were initially investigating their potential military applications as the Cold War (1945–1989) between the Soviet Union, the United States, and their respective allies intensified. By the mid-1950s, scientists concluded that fusion power had no uses in weaponry, and both Cold War superpowers declassified their fusion research programs and began collaborating on its further development as a potential energy source.

During the 1960s, scientists tested multiple fusion generator designs, which used varying strategies to deal with the unstable, superheated plasma created by the fusion process. One such device, the toroidal chamber with axial magnetic field or “tokamak,” was created by Soviet scientists. The tokamak emerged as the preferred fusion technology by the early 1970s, a time when much of the developed world was entangled in an energy crisis. At the time, researchers erroneously believed that existing versions of the tokamak offered the most direct path to breakthroughs that would make commercialized, scalable fusion power a feasible reality during an economic milieu marked by severe energy shortages. Scientists also concentrated a great deal of developmental effort into deuterium-tritium fuel, which supports fusion reactions at lower temperatures than other elements. However, the energy released by deuterium-tritium fission is comprised almost entirely of neutrons, which generate radioactive waste and require expensive, cumbersome technologies to convert into electricity. The combined effects of these miscalculations delayed the development of fusion power by decades, sending researchers back to observations made during the 1960s in search of alternative approaches.

One such observation noted that a technique known as aneutronic fusion released no neutrons whatsoever, with a type of hydrogen-boron fuel known as pB11 generating particularly efficient results without creating radioactive byproducts. However, aneutronic fusion required temperatures higher than the existing generation of tokamaks could support, leading researchers to divert a great deal of their resources to developing new tokamaks during the 1980s and 1990s. These efforts yielded innovative spherical tokamak designs, which were widely considered the most likely contenders for use in commercially feasible fusion power reactors. During the 2010s, fusion power enjoyed resurgent development interest due to its potential to provide simultaneous solutions to harmful carbon emissions and soaring global electricity demands. Public-private research and funding partnerships emerged, and dozens of international research groups convened with a renewed commitment to advancing fusion power technology. Their efforts yielded intriguing alternatives to formerly dominant tokamaks and the laser-powered fusion reactor technologies while advancing legacy technologies to new heights of efficiency and capability.

Overview

Spherical tokamaks and laser-powered reactors remain mainstays of current fusion power research. Modern tokamaks use a vacuum chamber shaped like a donut to exert extreme levels of heat and pressure on hydrogen fuel, changing the hydrogen’s physical state from gas to plasma. A network of magnetic coils surrounding the vacuum chamber then controls the motion of the charged particles in the plasma, forcing them to collide with one another. Meanwhile, the tokamak uses supplementary heating systems to drive temperatures in the vacuum chamber to fusion levels, which range from 150 million to 300 million degrees Celsius (270 million to 540 million degrees Fahrenheit). At these temperatures, the charged plasma particles are hot enough to overcome the electromagnetic forces that would otherwise repel them from one another, causing them to fuse into new particles. Upon fusing, the particles release tremendous amounts of energy, which is then collected and stored. Tokamaks use a strategy known as magnetic confinement fusion, which efficiently converts hydrogen fuel into energy that can be captured but cannot yet create self-sustaining reactions. The neutrons released by magnetic confinement fusion also damage the reactor’s interior-facing walls, necessitating design and engineering solutions that researchers have yet to discover.

Laser fusion uses deuterium-tritium isotopes as fuel, placing them in a compartment known as a blast chamber where they are bombarded with high-intensity laser beams. This creates superhot, compressed, ultrahigh-density conditions in the blast chamber, which triggers thermonuclear explosions that release energy that can be captured. It is a type of inertial confinement fusion, which generates energy with few byproducts and no carbon emissions but is also hampered by technological inefficiencies that cause significant proportions of the deuterium-tritium fuel to burn off before fusion can occur.

In 2010, the ITER Organization began building what will be the world’s largest tokamak. The project is based in southern France and according to ITER projections, the new tokamak will become operational in December 2025 and power up over the ensuring years to reach full power generation capacity by 2035. A simultaneous wave of research into alternative fusion power systems is also underway, with emerging technologies including magnetized target fusion, field-reversed configuration, and stellarators. Magnetized target fusion uses a hybrid model that combines magnetic and inertial confinement, while field-reversed configuration uses accelerators known as plasma guns to suspend plasma within its own magnetic field, theoretically improving the stability of the system. Stellarators function like tokamaks but instead use an intricate, looped ribbon design instead of a donut-shaped chamber, which could potentially allow the reactor to remain operational for longer periods.

Recent advancements have integrated computer simulations and other digital technologies to improve generator designs and efficiency, but scientists are still working to better understand and more precisely control the behavior of the superheated plasmas that result from fusion processes. These inefficiencies have thus far prevented scientists from achieving “breakeven,” or equal amounts of energy input and output. Thus, current fusion power technologies continue to use up more energy than they produce, necessitating research and engineering breakthroughs before it will become feasible as a commercial electricity source.

Impact

Optimistic projections suggest that fusion power could become a practical reality by the 2030s, though some experts believe it could take longer to solve the persistent engineering problems currently inhibiting energy breakeven. A decades-old quip defines longstanding scientific perceptions of fusion energy: “It is thirty years away…and it always will be.” Yet, current research has yielded promising advancements that have prompted some experts to predict breakeven could occur as early as the mid-2020s.

If commercialized on a large scale, fusion power would provide a stable, sustainable, and practically limitless solution to the world’s electricity needs. The ITER Organization notes that fusion reactions release as much as four million times more energy than fossil fuel combustion. They do so while drawing on safe, abundant natural resources present on Earth in quantities that would support continuous fusion power plant operations for millions of years. Furthermore, fusion power does not emit any carbon dioxide, effectively addressing concerns related to pollution and climate change. The radioactive byproducts produced by fusion reactors are reusable, recyclable, relatively stable, and have short half-lives, and system meltdowns are impossible.

ITER concedes that initial costs would be high, as scaling up fusion power technology would require a massive upfront investment. However, the organization notes that the electricity created by nuclear fusion would become less costly as economies of scale activate and the underlying technologies continue to refine and mature.

Bibliography

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“Fission and Fusion: What Is the Difference?” Office of Nuclear Energy, U.S. Department of Energy, 7 May 2018, www.energy.gov/ne/articles/fission-and-fusion-what-difference. Accessed 11 Mar. 2021.

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Walker, Kris. “What Is Laser Fusion?” AZO Cleantech, 10 Jun. 2013, www.azocleantech.com/article.aspx?ArticleID=419#:~:text=Laser%20fusion%20attempts%20to%20achieve,mixture%20at%20high%20energy%20density.&text=The%20kinetic%20energy%20produced%20by,thermal%20cycle%20to%20generate%20power. Accessed 11 Mar. 2021.

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