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JT-60SA: The world's largest nuclear fusion reactor ever built is located in Japan

Photo: AFP

In Japan, the world's largest temptation facility for a nuclear fusion reactor has officially been in operation since Friday. The JT-60SA fusion device in Naka, north of Tokyo, a Japanese-European cooperation project, will "bring humanity closer to fusion energy," said deputy project manager Sam Davis at the inauguration ceremony. It is "the result of a collaboration between more than 500 scientists and engineers and more than 70 companies across Europe and Japan."

EU Energy Commissioner Kadri Simson said that by the time the international test reactor Iter, which is being built in Cadarache in southern France, goes into operation, the plant in Japan will be the world's largest and most "advanced" tokamak type. Their commissioning is a "milestone in the history of nuclear fusion".

In nuclear fusion, atomic nuclei are fused together at extremely high temperatures. Enormous amounts of energy are released in the process. Conventional nuclear power plants, on the other hand, generate energy from the fission of atomic nuclei.

The fusion device in Japan is significantly smaller than the Iter test reactor in southern France, which is still under construction, and whose construction is repeatedly delayed. It consists of a donut-shaped container, the tokamak, in which plasma is heated to 200 million degrees Celsius. The aim is to cause hydrogen nuclei to fuse and release energy. In order to bring about nuclear fusion, a considerable amount of energy is required.

Investors promote nuclear fusion research

Although dozens of experimental reactors have been built since the 60s, only one plant has succeeded in generating more energy than is needed. In December last year, the National Ignition Facility (NIF) in Livermore, California, reported a "net energy gain" in trials. However, the U.S. plant uses a different technology than the JT-<>SA and Iter.

For supporters, this is just one of several recent important advances. Thomas Klinger, head of the "Wendelstein 7-X" fusion experiment near Greifswald, recently spoke to the dpa news agency of "milestones" in nuclear fusion research using magnets.

Markus Roth from the Technical University of Darmstadt, on the other hand, referred to the growing number of start-ups that are reviving nuclear fusion. In some cases, they have attracted private investments in the billions. Roth himself co-founded a German-American start-up in the field of laser fusion. In recent months, German politicians have pledged additional money for fusion research.

Alternative energy or inefficient and expensive?

In the long run, nuclear fusion could become a clean alternative to burning fossil fuels and controversial nuclear fission, according to proponents. Nuclear fusion has the potential to "become a key component of the energy mix in the second half of this century," said Commissioner Simson.

Critics, on the other hand, say the expectations are overestimated. Environmentalists criticize them as inefficient, time-consuming and expensive. Nuclear fusion is also too late as a possible energy source, and the focus should be placed more on renewable energy such as solar energy, grids or storage systems for the energy transition. In addition, nuclear fusion also produces radioactive waste, albeit to a much lesser extent than nuclear fission.