The European nuclear fusion plant “JET” (Joint European Torus) in Culham, UK, has set a world record for energy production. The reactor produced 69 megajoules of energy from 0.2 milligrams of fuel, said the Max Planck Institute for Plasma Physics (IPP) in Garching near Munich, which is involved in the project. This is the largest amount of energy ever achieved in a fusion experiment. “It would have required around two kilograms of lignite to produce the same amount of energy.”

However, this record did not produce a positive energy balance. Around three times as much energy was put into it as came out, said Athina Kappatou from the IPP. In addition to Germany and Great Britain, numerous other European countries are involved in the JET fusion plant. The project aims to gain fundamental insights into the construction of fusion power plants.

The principle of a fusion reaction is simple: As in the sun, hydrogen nuclei are fused into helium nuclei at high heat. The energy released by the sun supplies the earth with light and heat. A fusion power plant will also one day provide energy. According to IPP, accidents as devastating as those in nuclear power plants where atoms are split are not possible. In the event of a malfunction in fusion systems, the temperature would fall and the fusion reaction would immediately stop.

The road to usable nuclear fusion is still long

In practice, however, generating energy by fusing atomic nuclei is extremely complex: the basis is hydrogen atoms of different weights, so-called hydrogen isotopes. In the JET, the hydrogen isotopes deuterium and tritium are heated into an extremely hot plasma. The components of the atoms, the positively charged nuclei and the negatively charged electrons, are separated from each other. Because of the charges, the plasma can be kept suspended in a ring-shaped reactor by a very strong magnetic field. This is important so that it does not come into contact with the vessel walls and cool down. The temperature in the center of the plasma can be up to around 150 million degrees.

The extremely high temperatures are necessary so that the two positively charged atomic nuclei have enough energy to overcome their electrostatic repulsion and fuse. During fusion, neutrons are released, which contain a lot of energy. The aim of a fusion power plant is to heat water so that the steam can drive a turbine.

In fact, “energy gain” is not physically possible with JET and all other current magnetic fusion experiments worldwide, writes the IPP. “For these fusion systems to have a positive energy balance, they have to exceed a certain size.” This is only the case with the international fusion reactor ITER, which is currently under construction in southern France. Among others, China, Japan, the EU, Russia and the USA are involved in this project.

JET's operations have ended

The JET world record was already achieved on October 3, 2023. The reactor has thus exceeded its record of 59 megajoules set in 2021. The current record was a byproduct and not planned, explained Kappatou. It was more about answering various questions that are important for ITER.

According to IPP, the record experiment was one of the last at JET. After four decades, operations in Culham will cease at the end of 2023. “But the work for the researchers continues,” said Kappatou. The wealth of data collected by JET will keep them busy for years to come. In addition, we are now investigating how the plasma reacted with the material of the inner wall.

According to Kappatou, nuclear fusion is far from being a solution to the current energy problems. “But we know what the hurdles are. They can be solved. “Merger is not an insoluble problem,” she said.

“The idea is that in decades we will have a demonstration power plant that shows how electricity can be produced and fed into the grid,” said Kappatou. “This will produce usable electricity, but may not yet have the output that an entire large city needs.” As soon as this works, it can be expected that private companies will plan and build their own larger plants, “which will then produce similar amounts of energy as today's power plants can produce”.

There are also approaches other than the magnetic confinement of plasmas to obtain energy from controlled nuclear fusion. At the end of 2022, American researchers announced that they had obtained energy using lasers in a fusion facility: in the experiment at the National Ignition Facility (NIF) in In California, as is usual in research, only the energy balance of the plasma itself was given. This does not take into account how much current flowed into the lasers. According to information at the time, the California facility required about 300 megajoules of energy to deliver two megajoules of laser energy, which in turn produced three megajoules of fusion yield.