For a long time, fusion energy was characterized by a persistent cliché – always 30 years in the future, but never quite within reach.
The British-run company STEP Fusion has just pushed back against this cynicism with a stack of blueprints. The UK Atomic Energy Agency (UKAEA) has advanced its design for the STEP fusion plant, aiming to deliver clean, grid-connected fusion energy.
At the 34th Fusion Technology Symposium (SOFT 2026) in Aix-en-Provence, the UK’s flagship fusion program presented SPP3. This is the design iteration of the third generation of the “Spherical Tokamak for Energy Production” prototype system.
SPP3 prototype design
The core problem with the merger was rarely that it worked. The real hurdle is keeping the company running long enough to make a profit.
SPP3 changes this dynamic through its compact core apple-shaped spherical tokamak design. This steady-state architecture allows the facility to operate continuously, providing the uninterrupted flow of energy needed to reliably power the grid.
“This is all very difficult, but we have to keep the benefits in mind. We are intentionally addressing some of these technical challenges and uncertainties because they enable steady-state operation and practical maintenance,” said Sam Davis, head of engineering for the tokamak machine at STEP Fusion.
To bring this vision to life, engineers focused heavily on the facility’s giant microwave heaters, called gyrotrons. These systems bring the plasma to temperatures of over 150 million degrees Celsius. Increasing their efficiency means less energy is used just to keep the fire inside hot.
But creating a self-sustaining miniature star is only half the battle. You also have to repair it if it breaks.
Strong heat and high-energy neutrons quickly destroy the inside of the reactor. If it takes months to replace a part, a power plant becomes an expensive paperweight.
STEP’s answer is a “stacked rings” architecture paired with a vertical maintenance approach, which will be publicly demonstrated for the first time at SOFT 2026. Instead of peeling back layers of complex machinery like an onion, technicians can access components vertically within the container.
“These innovations are intended to simplify access to components on the ship, reduce maintenance downtime and support the high levels of availability required by future fusion power plants,” the press release states.
Advancing Britain’s energy goals
The risks remain high. The technology required to contain a star in a commercial network environment borders on the absurd.
“And of course we are doing everything we can to mitigate the risks in the meantime,” Davis added, “for example by testing everything we can.”
STEP Fusion is a ground-breaking UK technology and infrastructure program to build a prototype fusion power plant. This facility will demonstrate net energy production, fuel self-sufficiency and practical maintenance strategies, paving the way for a global fleet of commercial fusion facilities. Harnessing the natural process that powers the stars offers a safe, abundant, low-carbon solution to humanity’s growing energy problems.
The £2.5 billion project will be built on the site of a disused coal-fired power station in West Burton, Nottinghamshire, and is expected to add around 100 megawatts of net electricity to the national grid by 2040. Aside from the continuous power supply, SPP3 is designed to generate its own rare tritium fuel. It would ultimately prove that nuclear fusion can evolve from a sophisticated physics experiment into a repeatable, commercial energy fleet.
