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- China’s large Huanliu-3 nuclear fusion reactor follows decades of research in Chengdu.
- The world’s dozens of active tokamak experiments share ideas, scientists, and more.
- This tokamak, like many others, contributes to International Thermonuclear Experimental Reactor (ITER).
China joined the quest for an enormous, internationally cooperative nuclear fusion reactor in 2023. Now, they’ve reached a milestone by generating its magnetic field for the first time—a field that is entirely new in tis design. The “artificial sun” reactor, Huanliu-3 (HL-3), is a tokamak run by 17 collaborating labs and facilities around the world. But the much-ballyhooed quest to make energy using these huge reactors still has a decade or more to go, with a lot of misinformation in the mix.
While HL-3 puts China in the group of forerunners in nuclear fusion research, this reactor isn’t the largest (by far), and this milestone is only for its own timeline. This reactor is not close to operating consistently or producing energy that compares to the vast amounts of energy it and other similar reactors—known as tokamaks—require to operate. But HL-3, like many global tokamaks, is considered a proving ground for technologies that nations like China will offer to the truly world-leading ITER project in France. In that sense, each nation’s developments could make a difference going forward.
A tokamak is a donut-shaped (toroidal, in the science parlance) container that holds a stream of superheated magnetic plasma and is reinforced by massive magnets and supercooling encasement. The plasma—a cohesive “cloud” of atoms under star-like conditions—ends up hosting the same reactions that fuel the actual stars. The nuclei of atoms fuse together and release an enormous amount of energy... in theory. We know it happens in the stars, but we’ve never seen it happen in the same runaway, self-sustaining manner inside a thousand-ton piece of machinery on Earth.
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So, what does it mean for a world-class “artificial sun” tokamak reactor like HL-3 to establish its own, novel magnetic field design? Well, it’s a huge milestone within the field of tokamak research, as the magnetic field is what actually contains the superheated, fusion-generating plasma. Because plasma reaches a million degrees, it can’t make contact with any other material, or it will both instantly cool down out of the energy range and damage or destroy the part it touches. As such, a successful magnetic field is the only thing that will ever allow a tokamak to contain the plasma and keep it hot enough to make net energy.
There are a number of structural issues with how today’s tokamaks build their magnetic fields. The extremely huge electromagnets used in these machines are key to tokamaks’ designs (ITER received the most powerful magnet ever made in 2021), and they're under development all the time. But they all create hotspots that interrupt the plasma like an island in a stream—either because they are discretely installed at intervals around the shell of the tokamak, or simply because they’re made (by humans) of the naturally occurring materials we have on Earth.
In the cosmos, stars are not contained, so this never comes up. But in a generator, it's yet another hurdle to overcome.
All this means that a new configuration for a magnetic field can be a huge step forward, especially for HL-3, which is considered a feeder technology for ITER. Chinese media reports that China has signed on to build a vacuum chamber module for ITER. The vacuum vessel is essential to ITER’s goals, because it helps make the experiment plausibly safe to do—to contain a starlike reaction along the French waterfront.
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The language barrier and state-owned media both make it difficult to scrutinize Chinese projects like HL-3, and there aren’t a lot of meaningful comparisons between the world’s dozens of active projects in existence. China has another active nuclear fusion reactor in the international eye (Experimental Advanced Superconducting Tokamak, or EAST), which has been iterated upon China’s Hefei Institutes of Physical Science since the 2000s.
HL-3, however, comes from a lineage at Southwestern Institute of Physics in Chengdu, 900 miles west on the cusp of vast Western China. That program dates back decades as well, and both have steadily grown more and more powerful over decades of huge upgrades and rebuilds. HL-3 improves on previous designs, and is likely to get a larger machine with a larger overall amount of power going.
We still have never reached the threshold where a nuclear fusion reactor makes more energy than it uses, and to be honest, it’s not clear that we definitely will. But each step forward in proven tokamak technology brings the possibility of nuclear fusion energy closer to reality. And when we’re so many steps away, every little bit counts.
Caroline Delbert
Caroline Delbert is a writer, avid reader, and contributing editor at Pop Mech. She's also an enthusiast of just about everything. Her favorite topics include nuclear energy, cosmology, math of everyday things, and the philosophy of it all.
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