Why Fusion Energy Is the 'Dream Power' the World Has Chased for 70 Years

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Efforts to harness fusion energy are gaining momentum worldwide, driven by the global push for decarbonization. While nuclear power also produces no carbon emissions, fusion energy is often hailed as "dream energy" due to several advantages over conventional reactors:

It generates no high-level radioactive waste.
Its fuel can be abundantly extracted from seawater.
The system shuts down automatically in the event of a malfunction.

Despite its benefits, commercial fusion remains a formidable scientific challenge. Time and again, just as researchers seem on the brink of success, it slips further away. Yet today, with rapid technological advances, the long-awaited breakthrough may finally be within reach.

Nuclear Fission and Fusion

Nuclear fission — the process used in current nuclear power plants — involves splitting the nucleus of a heavy element like uranium, releasing heat. In contrast, nuclear fusion combines the nuclei of light elements such as hydrogen, producing even greater heat.

The Sun generates energy through hydrogen fusion, which is why fusion reactors are often described as creating a "Sun on Earth."

Japan's Fusion Research Facility

At the forefront of fusion research is the Naka Institute for Fusion Science and Technology in Ibaraki Prefecture, operated by Japan's National Institutes for Quantum Science and Technology (QST). It is home to JT-60SA, a tokamak-type plasma experiment device jointly built by Japan and European countries in 2020.

JT-60SA stands 16 meters tall, 13 meters wide, and weighs 2,600 tons. At its core is a 10-meter-diameter, doughnut-shaped vacuum vessel with a D-shaped cross-section measuring 6.6 meters vertically and 3.5 meters horizontally.

Surrounding the vacuum vessel are large superconducting magnets of two types. These magnets generate a magnetic field that creates an invisible cage, confining hydrogen and helium plasma within the vessel.

Plasma is a state of matter in which extreme heat separates atomic nuclei from their electrons. Hydrogen isotopes, which normally repel each other due to their positive charges, can overcome this resistance in a high-temperature, high-pressure reactor. When they fuse, a fusion reaction occurs.

Achieving a point where the energy generated by fusion surpasses the energy required to sustain plasma would mark a critical breakthrough on the path to practical fusion power.

Taming Plasma

However, controlling high-energy plasma is an immense challenge. While hydrogen bombs harness uncontrolled nuclear fusion triggered by atomic explosions, researchers aim for controlled fusion, where energy is released gradually and safely.

*Cross-section of fusion experiment JT-60SA. (©Sankei by Shohei Nagatsuji)*

Fusion research began in the United States and the United Kingdom in the 1950s. By the late 1960s, the Soviet Union introduced the tokamak — a device that became the global standard for fusion experiments.

The term "tokamak" is an acronym derived from four Russian words: tok (electric current), kamera (chamber), magnit (magnet), and others.

Today, most fusion experiments use tokamak reactors. The most prominent is ITER (International Thermonuclear Experimental Reactor), under construction in France since 2007. ITER is a collaboration among seven key participants: Japan, Europe, the United States, Russia, China, South Korea, and India.

Weighing 23,000 tons, ITER was initially set to begin operations in 2024, but its launch has been delayed until 2034. Amid these setbacks, its sister project JT-60SA has been gaining attention.

The World's Largest Fusion Device

In October 2023, JT-60SA achieved its first plasma generation, making it the world's largest and most advanced tokamak experiment. It plays a crucial role in refining plasma control technology for ITER.

*Control panel in the JT-60SA central control room, displaying the vacuum vessel during plasma generation. (©Sankei by Shohei Nagatsuji)*

With ITER's delays, countries like the United States, United Kingdom, Germany, and China have accelerated their independent fusion research, elevating it to a national priority. Japan, too, aims to demonstrate power generation with a prototype fusion reactor by the 2030s.

In the United States, a wave of startups focused on commercial fusion power has emerged, with Japan seeing a similar trend. These private companies bring fresh momentum to fusion development. Some specialize in key technologies, while others attract significant investment to speed up progress.

It remains to be seen whether private companies can succeed where ITER, backed by the world's top resources and expertise, has struggled to make faster progress.

Beyond tokamak reactors, fusion research also explores alternative methods, including helical and laser-based approaches. There is even potential for entirely new techniques to emerge.

For 70 years, fusion has been called the energy of the future. Now, the field seems to be undergoing a fundamental shift. If achieved, fusion energy would not only revolutionize global power but also alter the course of human history.

(Read the article in Japanese.)

Author: Shohei Nagatsuji, The Sankei Shimbun

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