The Joint European Torus (JET) was a magnetically confined plasma physics experiment, located at Culham Centre for Fusion Energy in Oxfordshire, UK. Based on a tokamak design, the fusion research facility was a joint European project with the main purpose of opening the way to future nuclear fusion grid energy. At the time of its design JET was larger than any comparable machine.

JET began operation in 1983 and spent most of the next decade increasing its performance in a lengthy series of experiments and upgrades. In 1991 the first experiments including tritium were made, making JET the first reactor in the world to run on the production fuel mix of 50–50 tritium and deuterium. It was also decided to add a divertor design to JET, which occurred between 1991 and 1993. Performance was significantly improved, and in 1997 JET set the record for the closest approach to scientific breakeven, reaching Q = 0.67 in 1997, producing 16 MW of fusion power while injecting 24 MW of thermal power to heat the fuel.

Between 2009 and 2011, JET was shut down to rebuild many of its parts, to adopt concepts being used in the development of the ITER project in Saint-Paul-lès-Durance, in Provence, southern France.

Immediately after the announcement of JET's closure at the IAEA conference in London, October 2023, the group "Scientists for JET" launched a petition to call for a review of the decision to close JET, with scientists fearing a research time gap and personnel loss between JET's closure and the start of ITER's operations. In 1975, the first proposals for the JET machine were completed. Detailed design took three years. At the end of 1977, after a long debate, Culham was chosen as the host site for the new design. Funding was approved on 1 April 1978 as the "JET Joint Undertaking" legal entity.

The reactor was built at a new site next to the Culham Centre for Fusion Energy, the UK's fusion research laboratory which opened in 1965. The construction of the buildings was undertaken by Tarmac Construction, starting in 1978 with the Torus Hall. The Hall was completed in January 1982 and construction of the JET machine itself began immediately after the completion of the Torus Hall. or 438 million in 2014 US dollars.

JET was one of only two tokamak models designed to work with a real deuterium-tritium fuel mix, the other being the US-built TFTR.

Both were built with the hope of reaching scientific breakeven where the "fusion energy gain factor" or Q = 1.0.

JET achieved its first plasma on 25 June 1983. On 9 November 1991, JET performed the world's first deuterium-tritium experiment. This beat the US's machine, TFTR, by a full two years.

Upgrades

Although very successful, JET and its counterpart TFTR failed to reach scientific breakeven. This was due to a variety of effects that had not been seen in previous machines operating at lower densities and pressures. Based on these results, and a number of advances in plasma shaping and divertor design, a new tokamak layout emerged, sometimes known as an "advanced tokamak". An advanced tokamak capable of reaching scientific breakeven would have to be very large and very expensive, which led to the international effort ITER.

In 1991, the first experiments including tritium were made, allowing JET to run on the production fuel of a 50–50 mix of tritium and deuterium. It was also decided at this time to add a divertor, allowing removal of waste material from the plasma. Performance was significantly improved, allowing JET to set many records in terms of confinement time, temperature and fusion triple product. In 1997, JET set the record for the closest approach to scientific breakeven. It attained Q = 0.67, producing 16 MW of fusion energy while injecting 24 MW of thermal power to heat the fuel, a record that endured until 2021.

The central Q, defined as the ratio of central fusion power produced to the central applied heating power, is computed using the TRANSP code for the record Q discharge to be Q approximately 1.3 (discharge 42976). The corresponding record values for TFTR are Q=0.26 and Q approximately 0.8 (discharge 80539).

In 1998, JET's engineers developed a remote handling system with which, for the first time, it was possible to exchange certain components using artificial hands only. A "Remote Handling" system is, in general, an essential tool for any subsequent fusion power plant and especially for the International Thermonuclear Experimental Reactor (ITER) being developed at Saint-Paul-lès-Durance, in Provence, southern France. This Remote Handling system was later to lead on to become RACE (Remote Applications in Challenging Environments).

In 1999, the European Fusion Development Agreement (EFDA) was established with responsibility for the future collective use of JET.

ITER design work

In October 2009, a 15-month shutdown period was started to rebuild many parts of the JET to adopt concepts being used in the development of the ITER project in Saint-Paul-lès-Durance, in Provence, southern France.

In mid-May 2011, the shutdown reached its end. The first experimental campaign after the installation of the "ITER-Like Wall" started on 2 September 2011.

On 14 July 2014, the European Commission signed a contract worth €283m for another 5-year extension so more advanced higher energy research can be performed at JET.

Post-Brexit

Brexit threw the plans for JET in doubt. As part of its plan to leave the EU, the UK was to leave Euratom, which provides the funding for JET. Talks on the funding after 2018, when the 5-year plan expired, commenced and a new agreement to extend JET's operation until 2019 or 2020 appeared to be largely complete. These talks were put on hold after the Brexit announcement. This guaranteed <abbr>JET</abbr> operations until the end of 2024 regardless of Brexit situation. In December 2020, a JET upgrade commenced using tritium, as part of its contribution to ITER.

In October 2023, JET set its final fusion energy record, producing 69.29 megajoules over 6 seconds from only 0.21 mg of D-T fuel. In November 2023, a petition asking that JET not be closed was started, with scientists fearing a research time gap and personnel loss between JET's closure and the start of ITER's operations. The final pulses were used to operate JET outside of its design capabilities. The decommissioning and repurposing process is expected to last until 2040. The scientists are concerned that JET's end date was set assuming that ITER would be up and running by that date to continue fusion experiments, but with ITER's startup being postponed and ITER's deuterium-tritium (D-T) reactions only scheduled for 2039, that there will be a gap of many years with no fusion research. with peak in excess of 1000&nbsp;MW. roughly the same amount of kinetic energy as a train weighing 5,000 tons traveling at . Each flywheel uses 8.8&nbsp;MW to spin up and can generate 400&nbsp;MW (briefly).

See also

  • Fusion power

References

Bibliography

  • JET pages on the EUROfusion web site
  • Poloidal field coils diagram
  • JET demonstrates alpha particle heating. Oct 2005 good graph
  • Culham Centre for Fusion Energy
  • The United Kingdom Atomic Energy Authority
  • IAEA's information about JET
  • Photos from JET Torus Hall

Sources

  • Fusion reactors explained by HowStuffWorks
  • T. Fujita, et al., "High performance experiments in JT-60U reversed shear discharges", Nuclear Fusion, Vol 39, p. 1627 (1999)