The German test reactor Wendelstein 7-X switches to continuous operation

There are great hopes for nuclear fusion around the world. Basically, this technology is about emulating the energy production of the sun on earth. So two hydrogen nuclei should fuse to form one helium nucleus. The hydrogen isotopes deuterium and tritium are mostly used for this. However, the two atomic nuclei are positively charged. So they repel each other. A merger only takes place under conditions that are extremely difficult to achieve. Inside the sun there is a pressure of 200 billion bar and a temperature of 15 million degrees Celsius. On the other hand, significantly less pressure can be generated on earth – which is why even higher temperatures are required. Specifically, the ignition temperature must be more than 100 million degrees Celsius. Then the existing matter changes into a plasma state and the atomic nuclei unite. The result: a lot of energy is released. Or in numbers: one gram of fuel can generate 90,000 kilowatt hours of electricity.

The Wendelstein7-X during construction in 2012. By Public Relations Department (Max Planck Institute for Plasma Physics) [CC BY-SA 3.0 (], via Wikimedia Commons

So far, a plasma could only be generated for around 100 seconds

That’s the theory. In practice, there are now two different technological approaches to achieve this goal: the tokamak reactors and the stellarators. The Iter research reactor is currently being built in the south of France. In this the tokamak approach is to be tested. With the test reactor Wendelstein 7-X in Greifswald, in turn, the basis for the construction of a stellarator is to be created. In 2018, the company succeeded in generating a plasma required for nuclear fusion for around 100 seconds. When later analyzing the experiment, some scientists took this as evidence that nuclear fusion actually works. Because many hopes have not been fulfilled in the past, this is now quite doubtful by some. Wendelstein 7-X, however, is an experimental reactor. It was therefore only designed for short experiments from the start. It has therefore been rebuilt since 2019 to enable a kind of continuous operation.

600 new cooling circuits had to be installed

This work has now been completed. The goal of the researchers: to generate a plasma for around half an hour. The step from 100 seconds to 30 minutes is huge. Among other things, 600 new water cooling circuits had to be installed to make this possible. There are also numerous additional obstacles to overcome from a technical and physical point of view. If this succeeds, however, it would be an important breakthrough. Because if a plasma can be generated for thirty minutes, then from a purely technical point of view this is also possible permanently. At this point, the question would then arise whether this would also make sense and be feasible from an economic point of view. However, experts warn against too much euphoria. They assume that decades of research will be necessary before the first operational fusion reactor can be found.

Via: ipp

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