Major obstacle to fusion energy cleared at Culham nuclear centre

Initial results from UKAEA’s new MAST Upgrade experiment at Culham, near Oxford, have demonstrated the effectiveness of an innovative exhaust system designed to make compact fusion power plants commercially viable.

With no greenhouse gas emissions and abundant fuels, fusion can be a safe and sustainable part of the world’s future energy supply.

Fusion energy is based on the same principle as stars creating heat and light. Using a machine called a tokamak, a fusion power station will heat a gas, or plasma, enabling types of hydrogen fuel to fuse together to release energy that can generate electricity.

A key challenge in getting tokamaks on the electricity grid is removing excess heat produced during fusion reactions.

Without an exhaust system that can handle this intense heat, materials will have to be regularly replaced – significantly affecting the amount of time a power plant could operate for.

The new system, known as a Super-X divertor, would allow components in future commercial tokamaks to last for much longer, greatly increasing the power plant’s availability, improving its economic viability and reducing the cost of fusion electricity. The concept for the Super-X divertor originally came from the Institute for Fusion Studies group at the University of Texas.

Tests at MAST Upgrade, which began operating in October 2020, have shown at least a ten-fold reduction in the heat on materials with the Super-X system.

This is a game-changer for achieving fusion power plants that can deliver affordable, efficient electricity.

UKAEA is planning to build a prototype fusion power plant – known as STEP – by the early 2040s, using a compact machine called the ‘spherical tokamak’. The success of the Super-X divertor is a huge boost for engineers designing the STEP device, as it is particularly suited to the spherical tokamak.

UKAEA’s lead scientist at MAST Upgrade, Dr Andrew Kirk, said: “These are fantastic results. They are the moment our team at UKAEA has been working towards for almost a decade.

“We built MAST Upgrade to solve the exhaust problem for compact fusion power plants, and the signs are that we’ve succeeded.

“Super-X reduces the heat on the exhaust system from a blowtorch level down to more like you’d find in a car engine. This could mean it would only have to be replaced once during the lifetime of a power plant.

“It’s a pivotal development for the UK’s plan to put a fusion power plant on the grid by the early 2040s – and for bringing low-carbon energy from fusion to the world.”

UKAEA www.ccfe.ukaea.uk