Artificial Sun Breaks Record in 'Landmark' Moment for Clean Fusion Energy

The Joint European Torus (JET)—the largest and most powerful operational fusion reactor in the world—has replicated the nuclear processes that power the sun, generating a record-breaking amount of fusion-based energy.

The UK Atomic Energy Authority (UKAEA) announced on Tuesday that scientists and engineers at JET had successfully generated 59 megajoules of sustained fusion energy. This more than doubled the record set at the site in 1997, when it produced 22 megajoules of energy.

The achievement represents the clearest demonstration thus far of the potential of fusion reactors—or Tokamaks—to generate environmentally clean and sustainable energy.

Emeritus Professor of Energy Conversion at the University of Newcastle, Ian Fells, commented on the breaking of this record: "The production of 59 Megajoules of heat energy from fusion over a period of 5 seconds is a landmark in fusion research.

"Now it is up to the engineers to translate this into carbon-free electricity and mitigate the problem of climate change."

What makes the breaking of this record particularly significant is these tests were conducted in a way that replicates what international nuclear fusion research and engineering megaproject tokamak ITER will do after it is completed in 2025, albeit on a much smaller scale.

Max Planck Institute for Plasma Physics researcher Athina Kappatou said in press release: "In the latest experiments, we wanted to prove that we could create significantly more energy even under ITER-like conditions."

What Makes Fission Energy So Clean?

Tokamaks are often referred to as "artificial suns" due to the fact they generate energy by fusing together the atoms of light elements, creating heavier elements with the difference in mass transformed into energy—the same process that powers energy radiated by the stars.

The process is almost the reverse of that conducted in the current generation of nuclear power plants, which create energy by breaking down heavy elements like uranium to create lighter elements, with the difference in mass changed to energy.

Unlike the expensive and dangerous materials used by the fission process, fusion uses heavy isotopes of hydrogen, deuterium, and tritium, the former of which is abundant in seawater and the latter which will be created in future plants from the element lithium.

Because deuterium is found in seawater, one liter of water could theoretically provide enough raw material for fusion to produce as much energy as the combustion of 300 liters of oil.

In tokamaks atoms of heavy hydrogen are forced together at high velocities to create helium, with the mass difference transformed to energy.

This means the by-product of the fusion process is helium, which is safe and non-radioactive—unlike some of the by-products of nuclear fission.

Amy Gandy, senior lecturer in Nuclear Materials Engineering at the U.K.'s University of Sheffield, said: "JET is the only fusion experiment in the world that uses the same fuel that will be used in future fusion power plants and so these new experiments have allowed researchers to test, for the first time, key components in real-life conditions - such as how the plasma and the materials that are nearest to the plasma the materials that make up the core of the fusion device interact.

"JET has been upgraded over the years to mimic many of the systems that will be used in ITER. These results therefore give confidence that ITER will achieve the promise of producing a self-sustained plasma capable of producing more energy that is put in."

Why Tokamaks Are Hotter Than the Sun

Handling tritium and getting JET closer to ITER requires changes to the vessel in which the plasma that hosts the fusion reactions is held. Between 2009 and 2011 the JET team replaced the carbon lining of the tokamak's plasma vessel with a more resistant mixture of beryllium and tungsten.

The new metallic wall means that the plasma stored in the vessel must be much tighter controlled, and the new results demonstrate success in doing this at temperatures around ten times that found in the sun.

Tokamaks have to be hotter than the sun because forcing together atoms to drive fusion requires a lot of energy. At the heart of stars, this is provided by an intense gravitational force generated by the stellar body's tremendous mass.

This can't be replicated here on Earth so, instead, researchers heat plasma to temperatures many times that found in stars, providing the energy for fusion in this way.

While this takes a lot of energy in of itself, as does generating the powerful magnetic field required to constrain the superheated plasma, it is predicted that when ITER is up and running it will release ten times as much energy as is fed into the plasma in terms of heating energy, using deuterium-tritium fuel.

The results from JET and the new energy record will be seen by many as confirmation of these hopes for ITER.

Tony Roulstone, researcher for the Department of Engineering at the University of Cambridge, said: "This is pretty important. JET held the fusion duration and
temperature records for many years but has been closed down for upgrades.

"Tokamaks in China and Korea have pushed ahead with fusion temperature and durations but these have not been deuterium-tritium reactions. They have been long duration plasmas to demonstrate fusion conditions without the fuel."

Roulstone explains that JET is in its last campaign and why this is significant for future fusion devices, particularly ITER. He said: "In this campaign, JET is seeking to get the best demonstration that ITER will work and the best information to support the design of ITER experiments.

"Often fusion over-calls advances in its experiments – not in this case."

Reader in Nuclear Materials at Imperial College London, Mark Wenman empathized the importance of the JET record in making clean fusion energy a power source of today, not the future.

He said: "For me, this means we can expect big things from ITER and that fusion energy really is no longer just a dream of the far future - the engineering to make it a useful, clean power source is achievable and happening now."

Artificial Sun and the Real thing
(Left) a view of the interior of the artificial sun tokamak JET. (Right) The real thing, Jet replicated the fusion process occurring in the sun to generate a record 59 megajoules of energy proof of principle for larger future tokamaks like ITER. NASA/UKAEA