Following UK media reports questioning the future of UK's Culham Centre for Fusion Energy (CCFE) and the Joint European Torus (JET) in the wake of the UK's expected withdrawal from the European Union (Brexit), CCFE head Ian Chapman said on 30 November that "nothing has changed". JET is the largest tokamak in the world and the only operational fusion experiment currently capable of producing fusion energy.

The JET facilities are operated by the CCFE under a contract between the European Commission and the United Kingdom Atomic Energy Authority (UKAEA), and collectively used by all European fusion laboratories under the EUROfusion consortium. European nuclear fusion research comes under the auspices of the European Atomic Energy Community (Euratom), which pre-dates the EU.

The Financial Times report had described the eventual decommissioning of the JET tokamak – along with associated radioactive waste – as a "potential flashpoint" in Brexit negotiations. The BBC said around 100 EU scientists from outside the UK are currently at the JET site and, according to Prof Steve Cowley, who was director of the facility until recently, many are "extremely nervous". He told the BBC: "We've certainly lost a few people already – these are highly talented people at the very forefront of scientific discovery and we can't afford to lose them.

He added: "This is the world's greatest fusion lab and if we don't find a way to make an agreement with Europe, this will all go – and our lead in this area will have been dissipated and I think that's an enormous shame. We'd be bonkers to close it down, and Europe would be bonkers to close it down, but these are uncertain times."

Chapman, who is also CEO of the UKAEA, said: "In light of recent media reports (notably on the BBC and Financial Times) on the impact of Brexit for the future of JET, I would like to be clear nothing has changed regarding the future for CCFE and JET." He added that discussions are continuing with UK government, which remains very positive about the fusion programme, while options for continued JET operation are actively being discussed.

“Although no firm decisions or commitments have been made, I know that the Government values the international collaboration in fusion and I remain confident for our long-term prospects, he said. "It is also worth noting that these discussions are helped enormously by excellent recent results on JET. Routine high heating powers and excellent machine reliability have led to plasmas with very high confinement and stored energy – by far the best results with the new Iter-like wall. This augurs very well for key experiments planned for 2019/20 using the fusion fuels deuterium and tritium, and is invaluable for the early operation of Iter."

The International Thermonuclear Experimental Reactor (Iter), now under construction in France, will be JET's successor in the pursuit of commercial fusion power. Since producing its first plasma in 1983, achieving the world's first release of deuterium-tritium fusion power in 1991, and setting the world record for fusion power of 16MW in 1997, JET has carried out important work to assist the design and construction of Iter and remains closely involved in testing plasma physics, systems and materials for the project.

JET's 2015-2016 experimental campaign, which ended on 15 November, included: the rehearsal of procedures for future tritium-tritium and deuterium-tritium experiments; a hydrogen campaign during which physicists learned about the dependence of plasma parameters on the mass of the hydrogen fuel used; and a high-power deuterium campaign. Upcoming campaigns will include tritium-tritium and deuterium-tritium experiments that will be crucial foundations for the operation of Iter.

Iter is currently scheduled to produce its first plasma in 2025 and start deuterium-tritium operations in 2035. Like JET, Iter will not demonstrate the use of nuclear fusion to produce electricity. That will be the objective of Iter's successor, the Demonstration Fusion Power Reactor, or DEMO, which will aim to demonstrate the continuous output of energy, supplying electricity to the grid. According to EUROfusion, DEMO is expected to follow Iter by 2050.