After decades, the milestone of controlled nuclear fusion has finally arrived.
For the first time in history, humans have achieved controllable nuclear fusion in which the output energy is greater than the input energy.
This process is called "ignition".
The first significant energy progress in human history was the control and utilization of fire.
Now we hold up the torch again, so that the artificial sun is no longer a fantasy.
Milestone in decades, big step for "artificial sun"
On December 13, California's Lawrence Livermore National Laboratory announced that it had successfully achieved "net energy gain" (that is, the energy produced exceeds the energy consumed) in a nuclear fusion reaction for the first time, on the road to controlled nuclear fusion Go one step further.
These unfamiliar terms may make people confused. Let us first understand the concept of "controllable nuclear fusion".
Nuclear fusion is the fusion of two lighter nuclei into one heavier nucleus, releasing energy.
The fusion reaction that is most easily realized in nature is the fusion of hydrogen isotopes—deuterium and tritium. This reaction has lasted for 5 billion years on the sun. Stars are actually natural nuclear fusion devices one by one.
▲ Picture from: istock
Compared with nuclear fission and burning fossil fuels, nuclear fusion has many advantages:
It does not emit carbon, and does not produce nuclear radiation and nuclear waste like nuclear fission; because nuclear fusion requires extremely high temperatures, once the temperature of the fuel drops, the fusion reaction will automatically stop; a small cup of hydrogen fuel can theoretically be used for a house Provide energy for hundreds of years.
Therefore, fusion energy is a nearly unlimited, clean and safe new energy source.
▲ Fusion is the energy source of the universe, which occurs in the core of the sun and stars.
What if humans could replicate the fusion reaction of the sun in a controlled way?
This vision of controllable nuclear fusion is commonly known as the "artificial sun".
The ultimate goal of controllable nuclear fusion is to allow deuterium, which exists in large quantities in seawater, to undergo nuclear fusion under high temperature conditions, to provide human beings with a steady stream of clean energy, to replace fossil raw materials and conventional nuclear energy, and to consume far less resources than solar and wind power. .
▲ Fusion reaction.
However, the sun's nuclear fusion is constrained by the gravitational field provided by its own gravity, which we cannot imitate on the earth. At the same time, the high temperature and pressure on the sun create the necessary conditions for the fusion reaction. Temperature compensation.
Relevant research began in the 1950s. What troubles scientists is that fusion reactions consume huge amounts of energy, and how to make the energy produced exceed the energy consumed. What is even more difficult is that the energy has to be output continuously and stably, not just a flash in the pan.
On December 5th, Lawrence Livermore National Laboratory, through the "inertial confinement fusion" technology, finally realized the "net energy gain" fusion reaction, a step closer to the artificial sun.
The researchers fired 192 giant laser beams into a gold-coated black chamber the length of an eraser, and the intense energy heated the container, which contained fuel particles the size of peppercorns, to more than 3 million degrees Celsius.
▲ The "target" of the laser is very small, but the "target chamber" is very large.
The laser is continuously reflected and heated, eventually producing X-rays . The X-rays peeled away the surface of the grain, triggering a rocket-like implosion that pushed temperatures and pressures to extremes only achievable in stars, giant planets, and nuclear explosions. and tritium fusion .
Finally, for an instant lasting less than a trillionth of a second, the energy of the laser input is 2.05 megajoules, and the energy of the neutrons produced by fusion is 3.15 megajoules, the latter divided by the former, and the energy gain is greater than 1.
Sustainable electricity, still in the distant future
Although the fusion reaction of "net energy gain" has been realized, it is still a long way to go before it can be practiced outside the laboratory environment and even put into commercial use.
First, the "net energy gain" only reflects the fusion reaction itself, not the 300 megajoules needed to power the laser . The conversion efficiency from electric energy to laser is very low, and if the ratio of output electric energy to input electric energy is calculated, the energy gain is less than 1.
Second, recreating this fusion reaction on the scale needed for energy production requires enormous resources.
▲ The National Ignition Facility (NIF), the largest and most powerful laser in the world.
And, the machines that will deploy the generated energy to the grid, engineers have yet to develop.
Therefore, nuclear fusion is still at least ten years away from commercial use, and it may be decades, and power plants are even far away.
At present, Lawrence Livermore National Laboratory's laser is only fired about once a day, and the cost is too high to build a viable power plant in a short time.
At a news conference, Lawrence Livermore director Kim Budil said the launch represented one fusion ignition, but much more needs to be done to achieve commercial fusion power generation, including "many fusion ignitions per minute." ignition".
▲ Artistic rendering of nuclear fusion.
Similarly, nuclear fusion cannot be put into climate protection anytime soon.
Julio Friedmann, an energy technology expert, pointed out that the results achieved now are very important. If the output energy is not greater than the input energy, it cannot be a source of energy. But it won't contribute meaningfully to climate reductions for the next 20-30 years, which is the difference between lighting a match and building a gas turbine.
To limit warming to the "safe line" of 1.5 degrees Celsius, we must achieve net-zero emissions by 2050. Relying on nuclear fusion to get rid of the climate crisis is a distant dream.
Riccardo Betti, a professor at the University of Rochester and an expert in laser fusion, likened this breakthrough in nuclear fusion to the first time humans knew how to refine oil into gasoline :
"You still don't have an engine, you still don't have tires, you can't say you have a car."
Humanity has taken a big step, but there may be tens of thousands of steps ahead.
For the next generation of clean energy, the world is gearing up
Over the past few decades, many countries have been advancing controlled nuclear fusion.
The inertial confinement mentioned above is one of the two mainstream solutions to realize controllable nuclear fusion, and the other is magnetic confinement.
In fact, magnetic confinement is currently the main direction for countries to attack controllable nuclear fusion. The "tokamak" device is the most famous method of magnetic confinement nuclear fusion.
Tokamak is a ring-shaped device driven by confined electromagnetic waves to create an environment and ultra-high temperature for fusion of deuterium and tritium, and to achieve human control of fusion reactions.
▲ "Iron Man" Ark reactor is controllable nuclear fusion.
The Ark reactor in "Iron Man" is a bit like a tokamak. The Ark reactor at the Stark Industrial Base and the mini-reactor on the chest of Iron Man's armor are all "magnetic confinement (nuclear) fusion reactors."
Although the controllable nuclear fusion technology and the tokamak device first originated abroad, our country has realized that the latecomers are ahead and are at the forefront of the world.
China's "artificial sun" EAST, which was built in 2006, is called the "Full Superconducting Tokamak Nuclear Fusion Experimental Device", also known as the "Oriental Super Ring". It was built by the Institute of Plasma Physics of the Chinese Academy of Sciences in Hefei, Anhui.
At the end of 2021, EAST achieved a long-pulse high-parameter plasma operation for 1056 seconds, during which the electron temperature was nearly 70 million degrees Celsius, setting a record for the longest high-temperature plasma operation of the Tokamak device at that time.
On December 4, 2020, a new generation of "artificial sun" device (HL-2M) independently designed and built by CNNC Southwest Institute of Physics was completed.
In October of this year, HL-2M made a breakthrough – the plasma current exceeded 1 million amperes (1 megaamperes).
In the future, the Tokamak fusion reactor must operate stably at megaamperes. Therefore, this breakthrough also marks that my country is getting closer and closer to fusion ignition.
The "artificial sun" is a major scientific issue of great concern to the world. In the face of the next generation of clean energy, countries are partnerships with stakeholders. The most representative one is the International Thermonuclear Experimental Reactor (ITER), which was launched in 2006. project.
It is currently one of the largest and most far-reaching international scientific projects in the world. China, the European Union, the United States, Russia, Japan, South Korea, India and other member states participated in it. The "artificial sun" jointly created by all countries is Currently the world's largest nuclear fusion reactor is located in Cadarache in southern France.
The assembly of the ITER body is expected to be completed in 2025, and in the next few years, ITER components will be transported from various member states to Karadashe. As one of the equal members, my country undertakes 9.09% of the work in the construction phase of ITER, and enjoys 100% of the right to use ITER's technical achievements.
▲ The construction status of ITER in 2018.
Coal, oil, and natural gas may be exhausted and cause environmental pollution; wind energy, water energy, and solar energy are limited by weather or geographical conditions; elements such as uranium and plutonium required for nuclear fission have limited reserves and will also produce radioactivity.
In contrast, controllable nuclear fusion technology is a future energy method that all mankind places high hopes on. It is known as the "ultimate energy source" because it can almost solve the energy problem once and for all. When it is actually put into commercial use, in addition to climate benefits, it can also bring cheap electricity to poor areas.
The prospect is bright, but the road is tortuous. I hope that in the foreseeable future, we can witness the rising of the "artificial sun".
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