UK and US to Sign Nuclear Fusion AI Pact at London Summit
A UKAEA-Princeton supercomputing deal is the centrepiece of bilateral fusion agreements expected this week, backed by a £2.5 billion UK investment push announced in May.
The UK and US are expected to sign a series of fusion energy agreements at a summit in London, with the first to establish a new supercomputing partnership between the UK Atomic Energy Authority and Princeton Plasma Physics Laboratory, Energy Voice reported on Sunday (2026-09-13).7
The summit follows the UK government's announcement of a record £2.5 billion investment in fusion energy technology in May (2026-05). Its Fusion Investment Prospectus, also published that month, projected the global fusion market could one day be worth between £3 trillion and £12 trillion. Energy minister Michael Shanks said the sector could support more than 10,000 UK jobs by 2030 while attracting inward investment for British businesses.7
Private investment has grown sharply in parallel. Global private investment in fusion rose from around $7 billion in 2024 to $10 billion in 2025, the International Atomic Energy Agency estimates. Google and German utility RWE each committed €25 million to European fusion startup Proxima as strategic industrial partners, according to Oilprice.com.1,5
The UK's domestic pipeline has been filling out ahead of the summit. UK Fusion Energy signed a £30 million contract with Dassault Systèmes in June (2026-06) to develop a digital twin for the UK's first prototype plant, using the company's 3DEXPERIENCE platform for virtual modelling before physical construction begins. The University of Birmingham's Electric Power Research Institute and industry partners separately launched a £2.63 million collaboration on fusion reactor shielding materials under the FURESHMA programme.4,7
In the US, Commonwealth Fusion Systems is targeting completion of its ARC demonstration reactor in Virginia after closing a $1 billion funding round. Mumgaard told Utility Dive in August (2026-08-24) that a subsequent string of commercial ARC plants would cost "more than $1 billion, though not as much as $10 billion, which is the scale of capital needed to do fusion seriously."6
China's Experimental Advanced Superconducting Tokamak, known as EAST, is reportedly on track to achieve ignition in 2027, according to Oilprice.com, which would put it ahead of any Western commercial device before the end of this decade. Fusion plasma must reach around 150 million degrees Celsius, many times hotter than the sun's core, making ignition technically demanding and a threshold no commercial plant has yet crossed.3
The cost record of large fusion and nuclear projects remains a caveat for investors. ITER, the international experimental reactor in France, has seen its projected cost rise from $18 billion to $32.4 billion in 2023 dollars, the US Congressional Research Service found. Nuclear projects globally average roughly 100% construction cost overruns, the IEA has reported. Fusion developers argue their technology avoids some of fission's civil engineering complexity, but that claim has not been tested against an actual construction budget or schedule.1,2
A bilateral government pact puts public resources behind the simulation and AI tooling that private developers also need. If the UKAEA-Princeton partnership produces shared modelling infrastructure, it could reduce development costs for the growing number of startups operating in both countries. The terms on which that infrastructure is made available to commercial players will be the detail worth scrutinising once the summit announcements are confirmed.7