A Tungsten Miracle Happened in the Heart of a Fusion Reactor
The sun-mimicking technology known as nuclear fusion hopes to create “limitless” energy by smashing light nuclei together using immense heat, but containing such hot plasma is proving tricky.
A tokamak reactor in France called WEST recently upgraded from a carbon interior to one made of tungsten and successfully contained plasma at 50 million degrees Celsius for six minutes at higher energies and densities than ever before.
The International Thermonuclear Experimental Reactor recently decided to make the switch from beryllium to tungsten for its inner wall, so any data gleaned from WEST will prove immensely useful.
Tungsten, represented unexpectedly by the letter W on the periodic table of elements (for wolframite, an ore where tungsten is often found), is proving to be quite the wonder material for fusion reactors. In April 2024, the Korea Institute of Fusion Energy announced that its KSTAR fusion reactor successfully sustained plasma at 100 million degrees Celsius thanks in large part to its Tungsten divertor (basically a tokamak exhaust port).
Now, another reactor in France is reporting a major tungsten breakthrough: its toroidal tokamak, clad in tungsten, successfully sustained a reaction at 50 million degrees Celsius for a full six minutes at higher energies and densities than its carbon-made competitors.
The reactor, based in Provence, France, is called the Tungsten (W) Environment in Steady-state Tokamak (WEST), and it’s the successor of the Tore Supra that sported an interior of graphite tiles.
While carbon has many benefits—chief among them being its high melting point—it may not be the best go-to material of choice for commercial reactors. That’s because carbon can retain fuel in the wall because of its relatively high atomic mass compared to tungsten. This doesn’t work because reactors also need to breed tritium from these reactions to create a sustainable fuel supply.
But tungsten has its own challenges, as even a small piece of it can cool the plasma. And when you’re trying to sustain temperatures seven times hotter than the sun, that's not a good thing.
“The tungsten-wall environment is far more challenging than using carbon,” Luis Delgado-Aparicio, the head of advanced projects at the Princeton Plasma Physics Laboratory which is a partner on the WEST project, said in a press statement. “This is, simply, the difference between trying to grab your kitten at home versus trying to pet the wildest lion.”
In order to record these results, the WEST team relied on a new hybrid photon-counting technology to monitor the plasma. Because tokamaks radiate x-rays, the set-up needed detectors that could study and analyze the plasma while contained, and the multi-energy soft X-ray (ME-SXR) camera delivered.
“We use the emitted X-rays and their intensity for plasma diagnostics, which allow us to understand how it moves, but also to measure its temperature, velocity, pressure, and density,” Delgado-Aparicio said in a press statement. “This is why we depend on reliable X-ray detectors in our work.”
The reactor is part of the Coordination on International Challenges on Long duration OPeration (CICLOP) program with the International Atomic Energy Agency. “This energy-resolving camera will open a new route in terms of analysis,” said the chair of CICLOP, Xavier Litaudon. “We will have the ability to measure the tungsten inside the plasma and to understand the transport of tungsten from the wall to the core of the plasma.”
Like KSTAR in Korea, the WEST reactor’s primary goal is to lay the groundwork for the International Thermonuclear Experimental Reactor (ITER), another nearby fusion reactor in France that hopes to finish construction by 2025.
In 2023, ITER decided to switch the material of the reactor’s inner wall from beryllium to, you guessed it, tungsten. ITER’s fusion neighbor, WEST, will hopefully have lots of Tungsten data to provide once ITER is fully operational.
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