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Controllable Nuclear Fusion: The Race to Replicate the Sun on Earth

China and the United States have engaged in intense competition in the field of controllable nuclear fusion, both announcing major breakthroughs in simulating nuclear fusion reactions of the sun.

August 28, 2023
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Linwen
Editor-in-Chief, The China Academy
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The scientific race for the power of the stars is not only heating up, it’s positively ablaze. Recent weeks have seen the United States and China, two global powerhouses, announce major breakthroughs in the field of controllable nuclear fusion. This process, which involves taming the fierce energy released via fusion of light atomic nuclei like hydrogen, has long been a tantalizing dream for energy scientists.

The United States’ National Ignition Facility (NIF), known as the behemoth of laser systems, has achieved a monumental feat: the first-ever ignition in history. This is akin to the fusion reactions becoming a self-fuelling engine, producing enough energy to sustain themselves while compensating for any energy losses. Comparable to harnessing a star’s energy, NIF used high-intensity lasers to superheat and squeeze a tiny fusion fuel pellet, inducing a short-lived but powerful burst of fusion reactions.

Just as the echo of this breakthrough was fading, China responded with an impressive advancement. Its new-generation “artificial sun,” Huanliu-3, achieved a high-confinement mode operation with a plasma current of a staggering 1 million amperes, the highest current ever for nuclear fusion. The Huanliu-3 device, a tokamak, uses magnetic fields to trap and squeeze a plasma of fusion fuel, creating temperatures about seven times hotter than the core of the Sun. At these scorching temperatures, the repulsive forces between nuclei are overcome, leading to nuclear fusion.

Although in dramatically different approaches, both of these breakthroughs bring us closer to a future of unlimited energy possibilities. The promise of controllable nuclear fusion is almost too good to be true: a clean, safe, and abundant fountain of energy. Unlike its cousin, nuclear fission, which involves splitting heavy atomic nuclei and results in long-lived radioactive waste and significant safety risks, fusion energy is clean and meltdown-proof. Furthermore, fusion requires minuscule amounts of fuel compared to fission, with the fuel sources being abundantly available in nature. Imagine a future where the energy from 300 liters of gasoline could be generated from just one liter of seawater!

But this dream, while tantalizing, is no cakewalk. Achieving controlled nuclear fusion requires mimicking the harsh conditions within stars, which naturally carry out fusion due to their immense gravity and size. On Earth, scientists need to create these artificial star-like conditions.

The two main techniques to achieve this are magnetic confinement and inertial confinement. Both methods use hydrogen isotopes as fuel. When these isotopes fuse together, they form helium and release a tremendous amount of energy in the form of heat and neutrons.

Magnetic confinement aims for a steady-state fusion reaction, providing a stable and consistent power output. However, the complexity and large scale of the device needed to maintain the plasma raises cost and operational challenges. Plasma instabilities, turbulence, and heat losses pose additional problems, especially when the current significantly increase, approaching the level of ignition. The higher the current, the harder to confine the plasma. For these reasons, the achievement of the high-confinement mode by Huanliu-3 represents a milestone, as it enables the current to reach 1 million amperes while maintaining plasma stability. The high current also brings it closer to the threshold of ignition, that is, producing net output of energy. Projects like this, as well as the international ITER project in France, in which China also participates, are making strides in this field, aiming to demonstrate the feasibility of fusion as a large-scale energy source.

Inertial confinement, on the other hand, aims for a pulsed fusion reaction, offering flexibility and scalability in power generation. However, it requires precise and synchronized laser pulses to compress the fuel pellet, which poses technical challenges. Issues with implosion symmetry, hydrodynamic instabilities, and laser-plasma interactions also need to be addressed. By producing more energy than it consumes, the NIF, a prime example of inertial confinement technology, is one step ahead in this race.

While both approaches have made considerable progress, there are still many scientific and technical hurdles to overcome before we can harness the power of the stars on Earth. The dream of developing a fusion reactor—clean, abundant energy with minimal environmental impact and no long-term radioactive waste—is within our reach. The journey to make controllable nuclear fusion a reality continues, promising a solution to the world’s energy problems. The race is on, and the finish line shimmers with the energy of a million suns.

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Linwen
Editor-in-Chief, The China Academy
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