JET nuclear fusion reactor sets new world energy record

EUROfusion scientists and engineers from the UK Atomic Energy Authority (UKAEA) have announced that the Joint European Torus (JET), the largest and most powerful operational nuclear fusion reactor called a tokamak, has produced the record of 59 megajoules of sustained fusion energy in the form of neutrons during a five-second phase of a plasma discharge.

During this experiment, the JET achieved a power output of just over 11 megawatts, averaged over five seconds. The previous energy record, set in 1997, was just under 22 megajoules of total energy and 4.4 megawatts of five-second average power. However, the maximum power of 16 MW reached briefly in 1997 has not been exceeded in recent experiments, as the emphasis has been on sustained fusion power.

The team used the same fuel mixture to be used in commercial fusion energy power plants. France’s largest project and future power plants aim to fuse deuterium and tritium hydrogen isotopes and release large amounts of energy in the process.

“We can very well explore the physics of fusion plasmas working with hydrogen or deuterium, so this is the world standard,” explains Dr Athina Kappatou of the Max Planck Institute for Plasma Physics (IPP). “However, for the transition to the international large-scale fusion experiment ITER, it is important that we prepare for the conditions there.”

The International Thermonuclear Experimental Reactor (ITER) is currently under construction in Cadarache, southern France, and should be able to release ten times more energy than is injected into the plasma in terms of heating energy, using deuterium-tritium fuel.

To achieve this new record, the European tokamak has undergone a profound transformation. The old carbon coating of the plasma vessel was replaced by a mixture of beryllium and tungsten, as is also planned for ITER, between 2009 and 2011. This modification allowed the researchers to produce a stable plasma with the fuel deuterium-tritium which released 59 megajoules of energy.

The experimental installation is too small to produce net energy, that is to say to release more energy than the heating systems provide. This will not be possible until the larger scale ITER experiment in the south of France is online. “The latest experiments at JET are an important step towards ITER”, concludes Prof. Sibylle Günter, Scientific Director of the Max Planck Institute for Plasma Physics. “What we’ve learned over the past few months will make it easier for us to plan experiments with fusion plasmas that generate far more energy than is needed to heat them.”

However, this success is a major step forward on the roadmap for fusion as a safe, efficient and low-carbon way to tackle the global energy crisis.

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