EUROfusion
Oxford’s Joint European Torus (JET) has performed its final fusion research experiments just over four decades after it delivered its first pulse on 25 June 1983.
JET is considered to be the world’s largest and most powerful operational tokamak, uniquely capable of incorporating tritium into its fuel mix. The facility is located in Culham, Oxfordshire, and managed by the UK Atomic Energy Authority (UKAEA).
The tokamak JET serves as a collaborative resource for all European fusion laboratories under the EUROfusion consortium and has been used to investigate the potential for carbon-free fusion energy.
The foundation stone for JET was laid in 1979. At that time, JET was an 11-nation project comprising Belgium, Italy, Luxembourg, France, Netherlands, West Germany, Denmark, Ireland, Sweden, Switzerland and the UK.
The facility consists of a tokamak fusion system with a doughnut-shaped vacuum chamber. It is in this chamber where, under the influence of extreme heat and pressure, gaseous hydrogen fuel becomes a plasma. In the facility, temperatures can reach levels 10 times hotter than the centre of the Sun.
JET was able to achieve the world’s first controlled release of fusion energy. The facility produced its first pulse or plasma in 1983, and went on to create the first deuterium-tritium plasma (DTE1) in 1991, reaching a record 1.8 megawatts. In 2021, it conducted the second deuterium-tritium experiments (DTE2) and reached a world record for sustained fusion energy at high power by producing 59 megajoules over five seconds, demonstrating fusion power plant potential.
EUROfusion
Within the last forty years, JET has produced over 103,000 plasmas. Its findings were key to the planning of the international fusion experiment ITER and DEMO, the demonstration fusion power plant currently under design by the European fusion community.
Now, JET continues to make history by becoming the world’s first fusion energy machine to be repurposed and decommissioned.
“This is the final milestone in JET’s 40-year history,” said UKAEA CEO Professor Sir Ian Chapman. “Those decades of research using JET by dedicated teams of scientists and engineers have played a critical role in accelerating the development of fusion energy.”
The UKAEA said that even on its final day of plasma it “continued to push scientific boundaries, firstly attempting an inverted plasma shape for the first time at Culham before deliberately aiming electrons at the inner wall to improve understanding of beam control and damage mechanisms”.
Fernanda Rimini, JET senior exploitation manager, added that the “decommissioning will look at analysing what has happened to the [reactor] materials and how they have changed”, with a view towards learning how to improve the maintenance of other fusion sites.
The UK has pulled out of the ITER project and the UK government has committed to spending £650m ($798m) on an alternative UK fusion programme between now and 2027, including the new STEP prototype fusion energy plant.
The repurposing and decommissioning process of JET is expected to last until about 2040.
