Fusion is the nuclear reaction that powers the Sun and the stars, when the collision of two light atomic nuclei lead to their fusion this leads to a large release of energy. While humans cannot recreate the gravitation that enables fusion in the Sun, scientists have worked for more than half a century on other approaches to harnessing fusion energy on earth, as a promising long-term option for sustainable, non-carbon-emitting energy.

The ITER Project is a fusion research collaboration of seven Members — China, Europe, India, Japan, Korea, Russia, and the United States — combining their decades of research to build together a nuclear fusion device of unprecedented size. Members contribute to ITER largely in the form of components, manufactured to demanding technical specifications in hundreds of factories, then sent to the ITER site in the south of France for assembly into a single experimental facility.

The ITER nuclear fusion device, a tokamak, will use superconducting magnets to confine, shape, and control a plasma made of two forms of hydrogen: deuterium and tritium. The plasma will be heated to 150 million degrees, the temperature needed for fusion to occur. ITER's design goal is to achieve and sustain Q ≥ 10, meaning the production of total power from fusion at a level at least 10 times greater than the external heating input needed to keep the plasma at its operating temperature. ITER will also integrate the many systems needed to test industrial-scale fusion.

ITER will be an experimental device and will not produce electricity. Ultimately, the goal is for fusion to be commercialized as a source of baseload energy. But for this to happen, significant challenges do remain beyond what ITER will be able to achieve: for example, the need for long-term neutron resistant plasma-facing materials, innovative design engineering to achieve efficient heat removal, the scale-up of tritium breeding and extraction, and enhanced remote maintenance systems. As the ITER Members have recognized from the beginning, these challenges demand the engagement of the world's best companies and research laboratories, and their leading experts.

The project is now in assembly phase. Most of the support systems are complete, and some have already been commissioned. Most of the largest components have also been completed its first-of-a-kind manufacturing. The D-shaped toroidal field magnets — half made by Japan, half by Europe — have been manufactured and delivered. The same is true of the ring-shaped poloidal field magnets, fabricated in China, Russia, and Europe. Four of six modules of the central solenoid, the cylindrical magnet at the heart of the tokamak, have been delivered from the USA. And five of nine sectors of the ITER vacuum vessel are now onsite, with repairs to the mating surfaces either completed successfully or on track.

In 2024, ITER submitted a new proposed baseline to our governance body, the ITER Council, and project execution throughout the year has been at an all-time high. Yet much remains to be done. The assembly of the ITER tokamak is expected to take about eight more years. Many opportunities for ITER contracts are still to come, for which world-class expertise will be needed — including industrial expertise which Japan can offer.

In recent years, we have witnessed the emergence of many private sector fusion initiatives and supply chains, supported by private sector investment. The progress made at ITER and other public research facilities, combined with the urgent need to replace fossil fuels on a global scale, has reportedly driven this surge in private sectors. ITER welcomes these efforts, including those that involve less tested, higher-risk concepts, as they are expected to complement publicly funded projects and contribute meaningfully to the global body of fusion R&D.

A critical element of fusion's success is the presence of a supply chain capable of meeting the unprecedented specifications of fusion devices. Key fields relevant to fusion include electromagnetics, cryogenics, gyrotrons and other forms of plasma heating, robotics, 3D visualization, metrology, precision control systems, materials science, and a broad range of advanced manufacturing techniques. In many cases, the breakthroughs needed to develop ITER's components have led to spin-offs benefiting medicine, health care, transportation, power electronics, and other fields.

In meeting their varied contributions to ITER, Member companies have created a de facto fusion supply chain. These advancements in expert knowledge and industrial manufacturing capabilities will need to be sustained and even expanded if fusion is to become a success. Japanese companies have contributed substantially: in manufacturing superconducting magnets, as noted, as well as the gyrotrons to be used in ITER's electron cyclotron heating, key aspects of neutral beam heating, the blanket remote handling system, the divertor outer target, and more.

The ITER Members share a common dream: a future in which fusion energy can be brought to fruition as a sustainable source of baseload power. For that dream to be fulfilled, it will take the best expertise of scientists and engineers globally. Japan is well-positioned to continue to be a strong contributor in this remarkable human quest.