Fusion Remote Handling: JET, ITER and ABB Robots

After JET ran deuterium and tritium fuel in late 1997, the inside of the machine was too radioactive for people to enter for about a year. From then on, parts inside the vessel had to be changed by machines that operators steered from a control room. That is fusion remote handling, and JET at Culham in England was the first tokamak to rely on it for a whole shutdown. This post follows how the work moved from engineers in pressurised suits to the two-armed MASCOT manipulator, what ITER and the planned STEP plant are doing now, including design news from October 2026, and where ABB robots could fit.

Inside the JET vessel at the end of the 2012/13 tile exchange shutdown, with the MASCOT manipulator on the left. Photo: EUROfusion / Wikimedia Commons (CC BY 4.0)

How JET's engineers learned to work without going inside

EURATOM set up the JET project in the late 1970s, and the machine at Culham in Oxfordshire made its first plasma on 25 June 1983. Until 1997 it ran mainly on hydrogen and deuterium, and that was deliberate. Those fuels did not make enough fusion energy to activate the torus, so people could still go inside and the machine could be rebuilt between experiments. Shutdowns were done by hand. Even in 1998, staff who serviced equipment in the sealed enclosures beside the vessel worked in fully pressurised suits and rubber gloves, and JET's engineers wrote that this fitting work was extremely difficult.

The JET fusion experiment at Culham in 1991, its vessel hidden among heating, cooling and measuring systems. Photo: EFDA JET / Wikimedia Commons (CC BY-SA 3.0)

JET's remote handling kit was first built for general repairs, and its designers kept a person in the loop. The Articulated Boom, a 10 metre robotic transporter with 18 degrees of freedom, carried the MASCOT servo-manipulator into the torus through a port. MASCOT's two arms copy the master arms an operator moves in the control room and feed back the forces they meet. It can handle 20 kg, and each arm can sense forces as small as 100 grams. A 50 kg winch sat between its shoulders, and small cameras rode on its forearms. During a 1996 shutdown the team used it to fit 33 divertor modules inside the real machine.

The MASCOT slave manipulator at JET, partly wrapped in plastic, 2007. Photo: Steve Parker / Wikimedia Commons (CC BY 2.0)

Late 1997 brought the real test. After the deuterium and tritium experiments, the dose rate inside the vessel was 4.5 millisieverts an hour, so a person would have used up a full year's JET dose allowance in two hours. Between February and May 1998, operators removed all 144 divertor modules and fitted 192 new ones without anyone entering the torus. It was the first fully remote shutdown of a fusion tokamak, and the equipment had only two significant faults. The work grew from there. For the ITER-like wall, fitted between 2009 and 2011, the remote team went from about 600 components in 20 weeks in 1998 to about 7,000 in a year.

MASCOT's two arms at work inside the JET vacuum vessel. Photo: The Naked Cat Fighter / Wikimedia Commons (CC BY-SA 4.0)

Where fusion remote handling stands in 2026

JET stopped operating in December 2023 after 105,842 pulses. Its decommissioning is expected to run until 2040, and MASCOT is still busy: UKAEA is using an upgraded version to take around 3,000 tiles and components out of the tokamak, and it has been retrieving 66 samples for analysis. JET's remote handling work later led to RACE, UKAEA's robotics centre at Culham, which started in 2014 with 69 engineers and now has more than 300. RACE runs a test facility for ITER robotics and works on maintenance for the STEP prototype plant and Europe's DEMO design.

Culham Science Centre in Oxfordshire, home of JET and of UKAEA's RACE robotics centre, 2019. Photo: UK Atomic Energy Authority via Wikimedia Commons (OGL v1.0)

ITER, the international tokamak under construction near Cadarache in southern France, plans a fleet of remote handling machines: robotic transporters, manipulators and tools that will handle parts of up to 45 tonnes and carry them between the machine and a hot cell. Once it runs, inspecting or changing parts in activated areas will only be possible remotely. Each divertor cassette weighs about 10 tonnes, and a dedicated mover has to carry it through a narrow tunnel, a job Finland's VTT has tested on its DTP2 platform in Tampere. On 19 October 2026 ITER said the first series inner vertical target for its divertor had been finished in Germany, armoured with 2,208 tungsten blocks.

The ITER construction site at Cadarache in France, 2017. Photo: Oak Ridge National Laboratory / Wikimedia Commons (CC BY 2.0)

None of the sources for this post shows an ABB arm inside a tokamak, so ABB's place in fusion is a possibility for now, and mostly outside the vessel. JET rehearsed its 1998 shutdown on a mock-up, and UKAEA's LongOps project now plans remote jobs in a virtual reality mock-up. ABB's RobotStudio does something similar for factory cells. It runs on a virtual controller that ABB describes as an exact copy of the real robot software, so a program can be tested in 3D before any arm moves. ABB's Integrated Force Control lets a robot hold a constant force against a part and search for the right position, which is the kind of feel MASCOT's operators supplied by hand.

Engineers plan a robot cell in RobotStudio with an ABB large robot behind them. Photo: ABB

What future fusion plants will ask of maintenance robots

In Britain the next machine is STEP, a prototype spherical tokamak power plant to be built by 2040 at West Burton in Nottinghamshire, the site of a former coal power station. On 9 October 2026 the STEP team said it had presented the third generation of its design at the Symposium on Fusion Technology in Aix-en-Provence. Much of it was about maintenance: a vertical maintenance strategy and a stacked rings layout, meant to make the parts inside the vessel easier to reach and maintenance outages shorter. Four days later the programme's annual report said nearly £120 million had gone into the design so far, and it listed robotics among the new opportunities for British industry.

Glowing plasma inside MAST, the Mega Ampere Spherical Tokamak at Culham, 2017. Photo: Eye Steel Film / Wikimedia Commons (CC BY 2.0)

UKAEA says robotics will shape the design, construction and maintenance of future fusion power plants, since less downtime means lower costs and more energy. VTT is already studying smaller robots that weld, vacuum, tighten bolts and open doors inside a reactor. Welding is routine work for factory robots, so ABB arms could plausibly take on jobs in the test halls and workshops around a fusion plant. The IRB 7710 and IRB 7720 carry 280 to 620 kg with path accuracy down to 0.6 mm, and the IRB 8700 handles up to 1,000 kg. For homes the payoff is indirect: a fusion plant that spends less time shut down sends more power to the grid.

Two engineers program an ABB IRB 7710 or IRB 7720 large robot with a FlexPendant. Photo: ABB

UKAEA lists the conditions its maintenance robots must cope with: dose rates up to 3 kGy an hour, components at 500 K, ports that reach 5 metres into the vessel, leftover magnetic fields of about 40 mT, vacuum, and materials such as beryllium and lithium. Every hour a plant stands idle adds to the cost. Skills are the other gap. JET's 1998 team met ten unplanned tasks after work had started, and people solved them through the manipulator. RACE now trains operators on a haptic simulator for work at JET, Sellafield and Fukushima, and the same skills carry over to nuclear cleanup.

A robotics class with ABB GoFa education cells and RobotStudio on screen. Photo: ABB

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