Shulou(Shulou.com)11/24 Report--

On December 15, the U.S. Department of Energy announced that researchers at Lawrence Livermore National Laboratory (LLNL) in California have produced a "net energy gain" in nuclear fusion reactions for the first time, meaning that the energy generated by fusion reactions is greater than the laser energy that promotes the reaction.

Human beings have been exploring nuclear fusion for decades, but for a long time, the fusion reaction has been unable to achieve the increase of net energy, that is, the energy consumed always exceeds the energy produced by the reaction.

Therefore, the United States announced the realization of fusion ignition for the first time, which immediately caused a sensation in the scientific community. There is an optimistic argument that there is a dawn to solve the energy problem once and for all, and that nuclear fusion is expected to be commercialized in decades or more, and it will bring real clean and unlimited energy to mankind.

Can the successful ignition of laser fusion in the United States solve the human energy problem?

Du Xiangyi, academician of the Chinese Academy of Engineering, said in an interview with Phoenix New Media that the purpose of the US national ignition device experiment is not to provide human beings with energy solutions, but to study nuclear weapons.

Lawrence Livermore National Laboratory 1. The dawn of solving the energy problem? Nuclear fusion imitates the principle of the sun by combining two lighter nuclei into a heavier nucleus, releasing a large amount of energy during the combination. Compared with fossil energy, nuclear fusion does not emit carbon dioxide. Compared with the widely used nuclear energy (nuclear fission), it does not produce nuclear waste and has very little radiation, so it is called the holy grail of clean energy.

Prior to this, the US National Ignition Facility has conducted many nuclear fusion experiments, and the best result is that the ratio of output to input energy is 70%, which is still a net energy loss. The difference this time is that the fusion reaction produces about 2.5 megajoules of energy, which is about 120% of the 2.1 megajoules consumed by the laser, and the output energy is greater than the input energy.

In response, US Energy Secretary Jennifer Granhom said that the first successful net energy gain in nuclear fusion reaction in the United States is a "milestone achievement". This achievement is expected to help mankind take a key step in the process of achieving zero-carbon energy.

However, du Xiangyi, academician of the Chinese Academy of Engineering, took a more cautious view of the experimental results than optimistic American experts. In an interview with Phoenix New Media, he said that the net energy gain achieved by the US national ignition device is a progress in scientific research, but it is still far from the goal of producing hundreds of times the high gain, not to mention turning into a truly clean, unlimited energy "artificial sun."

He also pointed out that the purpose of the US national ignition device test is not to provide mankind with ideas to solve the energy problem, but to study nuclear weapons.

It is reported that the US national ignition device is operated by the National Nuclear Safety Administration, which is in charge of nuclear weapons under the US Department of Energy, and its main task is to achieve a high-energy fusion reaction and provide guidance for the maintenance of the US nuclear weapons stockpile.

Du Xiangyi of Lawrence Livermore National Laboratory believes that the nuclear fusion gain of LLNL belongs to the category of fusion physics and is unlikely to provide a solution to human energy problems. He explained that the nuclear fusion that people really use for energy is a kind of non-explosive and controllable fusion.

According to the experimental analysis, the LLNL fusion reaction releases about 3.15MJ energy, which is about 54% more than the energy entered into the reaction and more than twice the energy previously recorded by 1.3MJ. However, although the fusion reaction produces super-3.15MJ energy, NIF consumes as much energy as 322MJ in the process, which is about 102 times that of 3.15MJ.

Second, compared with the United States, what is the current level of China's "artificial sun"? So far, there are two ways to make artificial sun: one is magnetic confinement fusion, and the other is laser fusion which is ignited successfully.

Du Xiangyi, academician of the Chinese Academy of Engineering, explained to us the principle of laser nuclear fusion. Researchers at the National Ignition Facility at Lawrence Livermore National Laboratory (LLNL) used 192 lasers to inject energy from both ends into a cylinder, where a target the size of half an air gun BB bullet was squeezed and the deuterium-tritium fusion fuel in the sphere was "ignited" to produce energy.

The specific application of magnetic confinement fusion is the tokamak device. After the tokamak is energized, a huge spiral magnetic field will be generated inside the tokamak, which will heat the suspended plasma to a higher temperature, and eventually lead to nuclear fusion.

Du Xiangyi pointed out that for the two technological routes, the mainstream understanding in the academic circle is that the magnetic confinement fusion of tokamak devices is more promising for commercial use, and it is the real technical approach to fusion energy.

At present, the world's largest "artificial sun" International Thermonuclear Experimental reactor (ITER), that is, uses a tokamak device. ITER is one of the largest and most influential international scientific research cooperation projects in the world, and it is also the largest international scientific and technological cooperation project in which China participates in an equal capacity.

In 2006, China, the European Union, the United States, Russia, Japan, South Korea and India jointly signed the International Thermonuclear Experimental reactor (ITER) project launch agreement. In November, China was responsible for the completion of one of the key components, the first piece of the first wall to enhance the heat load.

According to reports, China's nuclear energy development has implemented the "thermal reactor-fast reactor-fusion reactor" three-step strategy, with research on both magnetic confinement and inertial confinement fusion. At present, the research of magnetic confinement fusion technology in China is in the forefront of the world.

In December 2021, China's Hefei Oriental Super Ring achieved 1056 seconds long pulse high-parameter plasma operation, more than twice the previous record; in October this year, China's new generation of "artificial sun" HL-2M plasma current exceeded 1 million amperes, setting a new record for the operation of China's controllable nuclear fusion device, marking an important step forward in China's fusion ignition.

EAST is known as China's "artificial sun". 3. How far is it from using nuclear fusion energy? Regardless of the technological route, it is expected that it will take a long time for nuclear fusion to be commercialized and to turn the artificial sun into a reality.

Kim Budil, director of LLNL, said that the commercialization of nuclear fusion could take decades, and that fusion technology still had to overcome many obstacles, including achieving multiple fusion ignition per minute and having a robust driver system. "our calculations show that it is possible for the laser system to achieve the output of hundreds of megajoules, and there is a way to achieve the output target." But we are still a long way from achieving that goal. "

Du Xiangyi said that nuclear fusion has no fundamental obstacles, but the technology is more difficult. To use fusion energy on a large scale, the biggest challenge is to have high-density and high-temperature conditions, the reaction needs to last long enough, and scientists can significantly reduce their costs. "I am not as optimistic as fusion experts, but it can be seen in this century to build an artificial sun on earth."

Du Xiangyi also pointed out that how widely controlled nuclear fusion can be used in human life and work depends on how economic it is, and scientists around the world are still working hard to explore. However, the acquisition of energy by controllable nuclear fusion is only one of the ways for human beings to explore clean and sustainable energy, and other sustainable and clean energy can also be studied and utilized, such as solar energy, wind power, hydropower, geothermal and other energy.

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