Source: Energy & Management Powernews, August 10, 2022
After a complex reconstruction, a new phase of experiments begins in the fusion plant "Wendelstein 7-X". The Federal Research Minister visited the facility on this occasion.
Federal Research Minister Bettina Stark-Watzinger (FDP) assured further support for the basic research carried out in Germany for fusion technology during her visit to Greifswald. "Fusion is a huge opportunity for our energy supply and our independence," she said Aug. 9 at a ceremony at the Wendelstein 7-X large-scale research facility. There, researchers from the Max Planck Institute for Plasma Physics (IPP) are trying to mimic the sun's energy production on Earth.
The fusion of hydrogen (H2) into helium (HE) is to be harnessed as an alternative source of electricity. The occasion for the ceremony was the completion of a complex conversion that will now allow the experiments to be expanded. In the facility, hydrogen gas is admitted into a vacuum chamber, placed under extreme heat and electrically charged. Meter-high magnetic coils keep the so-called plasma in suspension and at a distance from the chamber walls.
30-minute plasma control as a goal
The heat generated during the fusion of atomic nuclei serves as an energy source. It can be converted into electricity by means of heat exchangers and steam turbines or dissipated as direct heat into heating systems. Wendelstein 7-X is the world's largest stellarator-type fusion facility. The next phase of experimentation involves maintaining the plasma for up to 30 minutes.
The plant itself does not yet supply fusion energy, but is used for basic research and is intended to demonstrate the power plant suitability of stellarator-type fusion plants. "It's about continuous operation. That's the real mission," said physicist and project leader Thomas Klinger. So far, researchers have achieved only 100 seconds of plasma duration under moderate conditions. The main assembly of Wendelstein 7-X was completed in 2014, and the first plasma was generated on Dec. 10, 2015.
To date, 1.3 billion euros in total costs
For prolonged operation at maximum temperatures of up to 50 million degrees Celsius, 600 water cooling circuits have been installed, he said. This is to cool the "tiles" of glass fibers inside the chamber. The heart of the plant is the ring of 50 magnetic coils about 3.5 meters high, which are cooled down to minus 270 degrees. Fusion power plants are nuclear facilities. However, no high-level radioactive waste is produced, only low-level radiation, Klinger said. The total cost of the "W 7-X" project, which was launched in 1996, has so far amounted to 1.3 billion euros, and the cost of the plant itself is 400 million euros. The project is financed by the German federal government, the German state and the EU.
With the new facility, plasma equilibrium and confinement should be of comparable quality to that of a tokamak of the same size. The tokamak type of fusion facility is being researched in Munich-Garching with the "Asdex Upgrade". There, the plasma is controlled not only from the outside by magnetic fields, but also by electric current flowing in the plasma. However, this causes the plasma to break down again and again as soon as the current flow is interrupted, which allows only short generation pulses without additional measures.
If it is possible to generate an optimal magnetic field, stellarators could be a technically simpler solution for a fusion power plant than tokamaks. This is because they could make continuous operation possible in a simple way. However, this cannot be answered theoretically and would have to be clarified experimentally in the "Wendelstein". A practical application in fusion power plants is not yet foreseeable.
Further information on the Project Wendelstein 7-X can be found on the page of the Max Planck Institute for Plasma Physics.
Author: Susanne Harmsen
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