For more than half a century, scientists have been trying to achieve a controlled thermonuclear reaction that produces energy from the synthesis of atomic nuclei under the influence of enormous temperature and pressure. This reaction produces far less radioactive waste than nuclear fission, and neutron-rich hydrogen fuel is relatively easy to obtain. There is progress in this area, but the timing of cost-effective thermonuclear reactors is constantly being pushed into the future.

Which scientists were wrong?

Plasma management is one of the challenges scientists are trying to overcome. When the fuel density rises above a certain value, the plasma becomes uncontrolled.

• 34 years ago, the so-called “Greenwald limit” was formulated experimentally.
• In 1988, Martin Greenwald obtained the fuel density limit based on the inner radius of the tokamak and the amount of electric current flowing through the plasma.
• All this time, the Greenwald limit was considered the law, and therefore calculations of the efficiency of thermonuclear reactors were based on it.

However, during theoretical and practical research, Swiss scientists came to the conclusion that Greenwald’s calculations were wrong. Plasma can withstand much higher fuel density with increased thermonuclear reaction power. The source writes that the maximum possible density of hydrogen fuel could be about twice the Greenwald limit.

Safe, viable synthesis conditions become easier to achieve. You can run any mod you want for the fusion reactor to work properly,
– says physicist Paolo Ricci from the Federal Polytechnic School of Lausanne.

ITER project

The discovery that thermonuclear reactors actually operate at much higher hydrogen plasma densities will also impact the large-scale ITER project currently being implemented in France in partnership with many countries around the world. It is an international experimental thermonuclear reactor currently under construction at Saint-Paul-le-Durans. The deadline for completion of construction and commencing use is now set at 2035.

The parties to the agreement are EU countries, India, China, Korea, Russia, the United States and Japan. Australia, Kazakhstan, Canada and Thailand also joined the cooperation.

ITER project construction site in 2018 / Photo Oak Ridge National Laboratory