Nuclear Fusion Reactor Completion Targeted for 2038; Developer Aiming for 100,000-Kilowatt Generation

The Yomiuri Shimbun

7:00 JST, March 16, 2026

The National Institute for Quantum Science and Technology (QST) plans to start constructing a prototype reactor for fusion power generation in the late 2020s, with 2038 the target for completion, according to its design outline seen by The Yomiuri Shimbun.

With the plan now compiled, progress in fusion power generation is likely to accelerate.

Nuclear fusion, a process that occurs in the Sun, happens when atomic nuclei fuse to generate a large amount of energy. One gram of fuel obtained through nuclear fusion is said to be equivalent to eight tons of petroleum. Furthermore, nuclear fusion power generation produces no high-level radioactive waste or carbon dioxide.

So far, nuclear fusion has not been practically applied, and competition to develop the technology is intensifying both domestically and internationally.

The government’s goal is to test fusion power generation in the 2030s.

When it is built, the prototype reactor will measure about 30 meters in both diameter and height, the same size as the International Thermonuclear Experimental Reactor (ITER), which Japan, the United States, Europe and others are currently constructing in France.

Under the QST’s initial plan, a reactor was designed to be 1.4 times the size of the ITER and scheduled to be commercialized around the 2050s. However, it has been downsized to bring the timeline forward.

There are three phases in the development of the prototype reactor: testing power generation integrating the fusion reactor and power generation facilities; testing technology to breed tritium — the fuel — in the reactor; and testing the reactor’s stable operations.

One year after completing the prototype, the QST aims to successfully generate power for several minutes, with a net output of about 10,000 kilowatts. It then aims to increase that output to about 100,000 kilowatts when the reactor reaches stable operations.

The outline also includes an overview of the reactor’s maintenance facilities, containment building and safety equipment. The site is expected to have an area of at least about 1 square kilometer.

The administration of Prime Minster Sanae Takaichi has positioned nuclear fusion as one of 17 priority investment areas in its growth strategy. Local governments are also becoming increasingly interested in this project, with the Ibaraki and Aomori prefectural governments last year expressing interest in hosting the prototype reactor.