Important Milestone for Fusion Energy

Monday 02 Jan 23


Stefan Kragh Nielsen
Associate Professor
DTU Physics
+45 46 77 45 34


Søren Bang Korsholm
Senior Scientist
DTU Physics
+45 20 64 55 61
Two of Denmark's leading experts in fusion energy comment on startling American research results.

On 5 December 2022, a group of American researchers at Lawrence Livermore National Laboratory in California succeeded for the first time in creating more energy from a fusion process than was used to start the process.

Two of Denmark’s most prominent fusion energy experts, Senior Researcher Søren Bang Korsholm and Associate Professor Stefan Kragh Nielsen from DTU, explain why the result is so interesting.

In mid-December 2022, an American fusion energy research result attracted major attention in Denmark and internationally. Could you briefly describe what the researchers have achieved?

The American researchers have achieved a remarkable result in fusion energy, raising expectations of when fusion energy can become a reality.

In short, fusion energy is a copy of the processes that occur in the sun and make it produce light and heat. Fusion energy occurs when atoms fuse and should not be confused with fission energy, which occurs in a nuclear power plant where very large atoms are split.

When atoms fuse in the fusion process, a large volume of energy is released that can be used to generate electricity.

Research into fusion energy has been conducted for several decades. The result from Lawrence Livermore National Laboratory is significant because the researchers have succeeded for the first time in using fusion to create more energy than has been used to make it.

How did the American researchers achieve the result?

In the US experiment, 2.05 megajoules were used to start the fusion. This resulted in an output of 3.15 megajoules. This is not a large volume of energy. It is roughly equal to the energy needed to boil one litre of water. But the important thing is the ratio of 1.5 times higher output than what was used to create the fusion processes.

The American researchers are working with a fusion energy technology called ‘inertial confinement fusion’ or laser fusion. The technology uses more powerful lasers aimed at a fuel pellet of hydrogen isotopes. In the American experiment, a total of 192 lasers and a ‘droplet’ of hydrogen the size of a peppercorn were used.

The outer layers of the pellet are heated to very high temperatures by the lasers, causing them to expand and press the interior atoms together. This creates fusion, in which the atoms fuse, thereby releasing a high volume of energy. The technology requires very high precision and only lasts a few nanoseconds. Put differently, the lasers were used to create—very briefly—conditions similar to those at the centre of a star/the sun.

As researchers in Denmark, for example here at DTU, you work with another fusion power technology. Why don’t you use the same technology—which seems to be successful?

There are two technologies for creating fusion energy. One is ‘Inertial confinement fusion’, which the American researchers have used. The other technology is to use ‘magnetic confinement fusion’, which usually takes place in a reactor—called a tokamak. Using this technology, the fuel (a plasma formed by hydrogen isotopes) is heated up to 200 million degrees C, while it is kept floating in a powerful magnetic field enclosing a large vacuum chamber. The temperature is 10-15 times hotter than the core of the sun and causes the atoms to fuse.

In Denmark, Europe, and Asia, we have typically used tokamak technology to try to create fusion energy. Tokamak technology makes it possible to keep plasma at the desired temperature for a longer time. In the long term, it will thus also be possible to scale up the technology so that it is not only usable by researchers in laboratories, but is developed into actual power plants that can function continuously and supply society with energy.

At the beginning of the year, there was a highly publicized result from the pan-European laboratory JET in the UK—which uses tokamak technology. What breakthrough did this concern, and is it comparable to the American discovery?

In February 2022, European (including Danish) researchers succeeded in using the tokamak JET—which is located in Oxford—to produce a total of 59 megajoules of energy by keeping the plasma going for five seconds. The biggest volume of fusion energy ever created in a laboratory. The 59 megajoules are almost 20 times more than the energy created by the American researchers using ‘inertial confinement fusion’.

The research results from JET further contribute to confirming the modelling codes used to predict performance in future experiments and power plants— such as ITER.

A giant tokamak, ITER, is currently being constructed in the South of France, backed by a total of 35 countries—including Denmark. When do you expect this project to produce results? And can we risk that the construction of ITER—to the tune of DKK 150 billion—turns out to be a failed investment, because, in future, fusion power will be based on inertial confinement fusion?

ITER will be the largest tokamak in the world. As many as 35 countries—namely all the EU Member States, Switzerland, the UK, China, India, Japan, Korea, Russia, and the United States—are behind this huge energy research project. ITER will increase tenfold the volume of energy generated by the fusion relative to the energy used to heat the fuel (i.e. a factor of 10, where the US results were a factor of 1.5). And it should be noted that this is with the tokamak in operation for up to one hour at a time.

ITER is still under construction and is expected to be completed within the next 4-5 years and to be able to deliver the desired results around 2035. However, it is important to emphasize that ITER is a research project where new opportunities may emerge that need to be seized along the way.

The recent US result with the inertial confinement technology is impressive. However, this does not change the potential of the tokamak technology, which seems to be more suitable as a future power plant. So we have no doubt that ITER is a sensible investment in fusion energy research and will help ensure green energy for the world in the future.

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