For a long time, controllable nuclear fusion has been considered "the ultimate energy source for mankind", but after more than 70 years of research, it is still in the experimental stage.
On December 5, 2022, local time, the Lawrence Livermore National Laboratory (LLNL) in the United States carried out a fusion ignition experiment, and a "miracle" happened. After the laser beam delivered 2.05 megajoules of energy to the cylinder, it delivered 3.15 megajoules of fusion energy.
"Ignition" is the energy produced by nuclear fusion that exceeds the energy entered by the laser beam, which is one of the necessary indicators for controllable nuclear fusion to come into reality.
"Only in this case, this device is expected to provide energy, not just a consumer." Wang Zhibin, an associate professor at the Sino-French School of Nuclear Engineering and Technology at Sun Yat-sen University, explained that the LLNL experiment proved scientifically that inertial confinement fusion could achieve a net energy gain.
"This result is a scientific success - but it is still a long way from providing useful, abundant clean energy." Tony Rolstone, a lecturer in nuclear energy at the University of Cambridge, commented on the British Science Media Centre.
What Does It Mean To Achieve “Ignition”?
As early as 2009, the US National Nuclear Security Administration built the National Ignition Facility (NIF) at LLNL in California to conduct the aforementioned experiments in a 10-story building about the size of three football fields.
The original goal of NIF was to achieve "ignition" in 2012, but it was not achieved on schedule. NIF has been controversial for years since then, and the industry once pessimistically believed that it might never "ignite".
Nuclear fusion is a form of nuclear energy and refers to the process by which two light nuclei combine to form a heavy nucleus and produce energy.
The reason why the sun can emit light and heat is to rely on the continuous generation of nuclear fusion to provide power. Splitting an atomic nucleus into two light atomic nuclei can also produce energy called nuclear fission. The well-known atomic bombs and nuclear power plants all adopt this principle.
Fusion fuel is abundant and readily available, deuterium can be extracted from seawater, and tritium can be produced from abundant natural lithium. Nuclear fusion will not produce highly radioactive nuclear waste, which is clean and safe.
Zhang Jie, an academician of the Chinese Academy of Sciences and a researcher at the Institute of Physics of the Chinese Academy of Sciences, described that "the deuterium contained in 1 cubic kilometer of seawater can produce energy through fusion reactions, which is equivalent to the total energy produced by all oil reserves on the earth." It will be a "once and for all" resolution for human energy demand if it can be developed.
In 1952, on an uninhabited island in the Pacific Ocean, the United States detonated the world's first hydrogen bomb, and the world saw the power of nuclear fusion for the first time.
But these energies are released instantaneously. If they want to be used as energy for civilian use, the energy must be released slowly, orderly, and under control.
Extremely harsh conditions are required for two nuclei to overcome electrical repulsion and combine. Taking the sun as an example, its center has an ultra-high temperature of as high as 15 million degrees celsius and an ultra-high pressure of about 300 billion atmospheres.
Controlled nuclear fusion is often referred to as an "artificial sun" and needs to simulate the environment at the sun's center. There are two mainstream technical paths to realize controllable nuclear fusion: magnetic confinement fusion and inertial confinement fusion.
Controlled nuclear fusion is often referred to as an "artificial sun" and needs to simulate the environment at the sun's center. There are two mainstream technical paths to realize controllable nuclear fusion: magnetic confinement fusion and inertial confinement fusion.
In the 1950s, Soviet scientists developed an "alchemy furnace" shaped like a doughnut, known as the Tokamak device. It builds a magnetic field in the annular ring to confine the nuclear fuel so that it does not come into contact with the high-temperature container wall and can continue to burn for a period to generate energy. Since then, there has been an upsurge in the construction of tokamaks worldwide. The United States, Europe, Japan, and China have all spent vast sums building such large-scale devices.
In inertial confinement nuclear fusion, a huge pressure is generated by a laser so that the volume of the nuclear fuel becomes smaller in an instant, the density becomes more extensive, and the nuclear fusion reaction occurs.
How Far Is the Artificial Sun From Reality?
Wang Zhibin mentioned that from the perspective of obtaining large-scale and economical energy, magnetic confinement nuclear fusion is closer to being applied to human life than inertial confinement nuclear fusion. If there are other vital breakthroughs in inertial confinement nuclear fusion, that's another story.
"The purpose of the two technical paths is different." Wang Zhibin introduced that the magnetic confinement nuclear fusion based on the tokamak device is more like "burning coal balls". The construction goal is a fusion reactor that can output energy and be used for power generation. Inertial confinement nuclear fusion is more like "strike a match"; the process is close to a nuclear explosion, and critical parameters can be obtained through the research of these devices.
Science magazine bluntly stated on December 13 that NIF has never been planned for commercial power generation. Its primary function is to create miniature nuclear explosions and provide data to ensure the safety and reliability of the US nuclear arsenal.
On December 13th, 2022, the U.S. Secretary of Energy also mentioned that NIF's work helps solve humanity's most complex and pressing problems, including "maintaining nuclear deterrence without nuclear testing."
In a paper published in August 2022, Xu Mingyi, an associate professor at the School of Water Resources and Hydropower at Wuhan University, mentioned that for reasons of national defense and strategic security, countries and regions such as the United States, China, the European Union, the United Kingdom, and Japan are conducting relevant research. Including NIF in the United States, Shenguang III, the most significant laser fusion driver in operation in China, is another example.
In February 2022, JET, the world's largest tokamak device in operation, achieved a total of 49 megajoules of nuclear fusion for 5 seconds in the experiment, breaking its record in 1997.
Wang Zhibin emphasized that the current controllable nuclear fusion has only verified the feasibility of science. In the future, fusion demonstration power plants need to be built first to demonstrate engineering feasibility.
However, this type of power station has high investment and construction costs, and the price of power generation is much higher than that of coal power or photovoltaic power generation, making it difficult to commercialize.
Ultimately, the cost of power generation by controllable nuclear fusion should at least drop to a price similar to that of existing energy sources before market competitiveness emerges.
Wang continues to explain that "Controllable nuclear fusion may indeed be the future energy source of mankind, but it is very challenging to realize it at the industry level, but it is also possible that this kind of energy will be used in 100 years."
China’s Role in the Controllable Nuclear Fusion Projects
In China, scientists have started fusion research since the 1950s, and China's first tokamak device was built in the 1980s.
In the 21st century, EAST was designed by the Institute of Plasma Physics of the Chinese Academy of Sciences in Hefei, Anhui, and became the world's first fully superconducting tokamak device.
In addition, there are also Tokamak devices such as China Circulator No. 2 A (HL-2A) and China Circulator No. 2 M device, which were constructed by the China National Nuclear Corporation Nuclear Industry Southwest Institute of Physics and put into experiments in Chengdu.
Wang Zhibin said that in the development of controllable nuclear fusion, China followed suit in the past, but now it is running alongside Europe and the United States. A key node is that in 2007, China joined the International Thermonuclear Experimental Reactor (ITER) program.
China, the European Union, India, Japan, and the United States plan to jointly build the world's largest superconducting tokamak experimental reactor in France. Among them, China undertakes 18 procurement packages in the project's construction phase, that is, the manufacture of equipment parts. The project started construction in 2010 and is scheduled to be completed in 2025.
It is generally believed in the industry that after the successful operation of ITER, international nuclear fusion research will take a big step forward. But how far is the "artificial sun" from being applied? Perhaps it can be answered by borrowing a joke that has been popular for more than ten years in the industry, "nuclear fusion power generation only takes 20 years, and it will always be like this."
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