Case history – GRE and Tokamak Energy


Tokamak Energy is a pioneering research team, developing a unique solution to commercialise fusion power. In the race to find sustainable energy sources, fusion can generate plentiful, safe and clean energy by recreating the process that powers the sun. Fusion forces together hydrogen atoms (heavy hydrogen, typically deuterium and tritium). They combine to produce helium, one spare neutron and an immense amount of energy. On Earth, this typically takes place at immense temperatures inside a tokamak.

Fusion is a desirable energy source because the fuels will last for millions of years, the process doesn’t produce atmospheric pollutants or radioactive waste, and fusion plants are expected to be more space-efficient than other renewables. The achievement of fusion electricity would enable the provision of clean and sustainable energy around the world.


Tokamak Energy have been constructing a new world-leading fusion experiment –the ST40 tokamak. A tokamak uses high magnetic fields to trap the fusion fuel in a ring, where it is heated to millions of degrees. The magnets are made of copperpieces that spiral around the ring and produce the magnetic field when current flows through – a huge current of up to 6MA, which heats the copper considerably.

The researchers required a cooling system to manage this excess heat – returning the system to ambient temperature and, in a second phase, cooling it to below ambient temperature under controlled conditions.

A further challenge was that the system would be live at several thousand volts, ruling out traditional cooling water techniques for safety reasons. Pure water would be required to minimise conductivity.

Tokamak Energy approached GRE Ltd to produce a custom-designed cooling solution for its ST40 tokamak.

With no off-the-shelf product (or combination of products) available to Tokamak Energy, and construction unable to proceed without an operational cooling system, an entirely new solution was required.



Working in partnership withthe client, GRE defined the scope of the required solution as:

  • Ultra-pure water cooling system with user-controlled variable conductivity
  • On-board refrigeration sub-circuit to provide cooling below the ambient temperature
  • Integrated free-cooling circuit to provide cooling at above the ambient temperature
  • Rapid response time when system instructed to engage over modbus via the customer’s main control system
  • Ability to stabilise the system at the resultant high temperature (around 70°C) andcontrol the rate of cooling back to ambient at a specified rate to prevent thermal fatigue

GRE’s multi-discipline team of engineers grasped the problem at hand and developed a self-contained system that could meet the exact demands while providing the variable parameters required by Tokamak Energy’s researchers. GRE’s team identified the opportunity to design and deliver a free-cooling sub-system. Thisexploits the ambient temperature for cooling rather than using refrigeration, aligning with Tokamak Energy’s green vision and values.

The final system design was brought to life at GRE’s Devon headquarters and simulation-tested under controlled conditions with full test reports submitted to the client. As part of GRE’s end-to-end service, GRE engineers remained on callthroughout installation and commissioning to adapt and customise the system further, to ensure it hit every technical requirement. GRE’s own control system was integrated as a sub-system of the client’s controls, allowing complete access and flexibility in managing the cooling process.


GRE’s creative response to Tokamak Energy’s challenge delivered a multi-faceted cooling system that is the first of its kind. It has allowed Tokamak Energy to continue its ground-breaking research. In the absence of GRE’s solution, the researchers may have been forced to adopt multiple proprietary systems from several providers. This would have produced system conflicts and ongoing errors that would have interrupted testing, causing research delays. GRE’s bespoke system ensured that the cooling system operates as and when needed, in harmony with existing systems.


“GRE was recommended to us by our consultant, Monroe Brothers, who had worked with the team in the past. GRE’s experience with other customers gave us confidence to place the contract with them to provide a chilled water solution to a specific specification. Richard and the team visited us on several occasions to discuss our requirements and make recommendations, and kept up excellent communication during manufacture, providing us with weekly updates. The equipment will be installed at our new premises in early 2018 and we feel assured that GRE will support us throughout the commissioning process.”


Graham Dunbar, ST40 Project Manager