·Lawrence Livermore National Laboratory in the United States achieved a net energy gain in a recent fusion experiment, where the energy produced by nuclear fusion exceeded the input laser energy. This achievement will improve the ability of the United States to maintain its nuclear weapons without nuclear testing, and may one day use laser fusion as a source of zero-carbon energy.
Even if American scientists realize the net energy gain of nuclear fusion reaction, it does not mean that we will soon have cheap nuclear fusion energy, and it is still far away from commercial use.
A technician inside the preamplifier support structure of the National Ignition Facility at Lawrence Livermore National Laboratory, USA. Image credit: Lawrence Livermore National Laboratory
U.S. Secretary of Energy Jennifer Granholm and Under Secretary for Nuclear Security Jill Hruby at 10:00 EST on December 13 ) will announce "a major scientific breakthrough".
The news conference was attended by officials from various agencies of the US government, including Arati Prabhakar, director of the White House Office of Science and Technology Policy, as well as the US National Nuclear Security Administration and Lawrence Livermore. An official of Lawrence Livermore National Laboratory (Lawrence Livermore National Laboratory).
The Financial Times reported on December 12 that scientists at Lawrence Livermore National Laboratory have made a breakthrough in the field of nuclear fusion energy, achieving the first net energy gain of nuclear fusion reactions - the energy generated from nuclear fusion reactions More energy than it consumes, which is a key step towards the goal of unlimited zero-carbon energy, which may bring abundant energy sources in the future.
U.S. scientists have made a breakthrough in the field of nuclear fusion energy
The Financial Times reported that the Federal Lawrence Livermore National Laboratory in California achieved a net energy gain in a fusion experiment in the past two weeks. The energy exceeds the input laser energy.
The lab uses the inertial confinement fusion method, in which the world's largest laser beam hits a tiny particle of hydrogen plasma. The nuclear fusion reaction at the National Ignition Facility (NIF) in the United States produced about 2.5 megajoules of energy, about 120% of the 2.1 megajoule energy of the laser, and the relevant data is still being analyzed. The energy output was higher than expected, which damaged some diagnostic equipment and complicated analysis, two of the people said. The breakthrough has been widely discussed among scientists, the people said. According to the "New York Times" report on the 12th, an unnamed government official said that NIF's fusion experiment achieved ignition, that is, the fusion energy produced was greater than the laser energy that initiated the reaction. Ignition is also known as energy gain. A scientist familiar with the results also confirmed that NIF had achieved ignition. The development would improve the United States' ability to sustain its nuclear weapons without nuclear testing and could one day use laser fusion as a source of zero-carbon energy, the report said.
Stephen Bodner, a retired plasma physicist who has long been critical of the NIF, said a scientist friend messaged him that Lawrence Livermore National Laboratory achieved a net energy gain, The results will be announced on Tuesday, "They deserve credit for achieving their goals."
Schematic diagram of controlled nuclear fusion. Image credit: FT
What is nuclear fusion?
Nuclear fusion reaction is a common phenomenon in the universe, it is the source of energy for stars such as the sun.
nuclear fusion is a nuclear reaction form that combines two lighter nuclei to form a heavier nucleus and a very light nucleus (or particle). Two lighter nuclei produce mass deficit during the fusion process and release huge energy. When fusion occurs, two light nuclei repel each other because they are both positively charged. However, two nuclei with high enough energy meet head-on, and they can be packed quite closely togetherSo that the nuclear force can overcome the Coulomb repulsion and a nuclear reaction occurs, this reaction is called nuclear fusion.
The internal temperature of the sun and many stars is as high as tens of millions of degrees Celsius, and violent nuclear fusion reactions are taking place every moment. The energy released by the sun per second is about 3.9×10^26 joules. Although the energy that reaches the surface of the earth is only one billionth of the energy released by the sun per second, it is also a huge energy. It is this energy that makes the earth All life activities are possible.
Nuclear fusion energy is also the frontier direction of energy development in the world. Nuclear fusion energy is regarded as the future because its fuel comes from seawater, its efficiency is tens of millions times that of fossil energy, there is no long-term nuclear waste , and there is no carbon emission. The "ultimate energy source" of society. If human beings can control this energy, they can get rid of the current energy and environmental crisis on the earth. The raw materials needed for
controlled nuclear fusion are two isotopes of hydrogen, deuterium and tritium. Deuterium can be extracted from seawater, and tritium can be produced from lithium, which is very abundant on Earth. The energy produced by deuterium contained in one cubic kilometer of seawater through fusion reaction is equivalent to the total energy produced by all oil reserves on the earth.
However, if human beings want to successfully realize controlled thermonuclear fusion and reactions on the earth to obtain huge energy, they must create three necessary conditions. One is the extremely high temperature, so that the deuterium-tritium fuel can become a hot plasma exceeding 100 million degrees Celsius; the other is the extremely high density, so that the probability of quantum tunneling of the deuterium-tritium nuclei becomes larger, and it is convenient to transfer The alpha particle energy produced by fusion stays and continues to participate in the nuclear fusion reaction; the third is that the plasma is confined in a limited space for a long enough time.
So far, human research on controlled nuclear fusion is mainly divided into two categories. One is magnetic confinement nuclear fusion , that is, using a special form of magnetic field to confine the ultra-high temperature plasma in a state of thermonuclear reaction, which is composed of deuterium, tritium and other light nuclei and free electrons , in a limited volume, making it subject to A large number of nuclear fusion reactions occur in a controlled manner to release energy. A typical experimental device is the All-Superconducting Tokamak Nuclear Fusion Experimental Device (EAST) of the Hefei Institute of Material Science, Chinese Academy of Sciences. The second is laser nuclear fusion, which is inertial confinement nuclear fusion driven by high-power lasers. Typical experimental devices are the Shenguang Laser Facility in my country and the National Ignition Facility in the United States.
Will humanity have cheap fusion energy soon?
The US$3.5 billion National Ignition Facility, located at Lawrence Livermore National Laboratory, was originally designed to test nuclear weapons through simulated explosions and later to advance fusion energy research . Proponents say it could advance fusion research, which could lead to commercial power plants.
The NIF, which covers an area as large as three football fields, adopts a center-ignition laser fusion scheme, consisting of 192 huge lasers that fire simultaneously at a metal cylinder. The cylinder is heated to about 2.82 million degrees Celsius, producing X-rays imploding, heating and compressing the deuterium-tritium fuel, and triggering nuclear fusion.
NIF started formal ignition experiments in 2010. In 2014, scientists at Lawrence Livermore National Laboratory achieved results, but at the time the energy generated was so small that it was equivalent to the energy consumed by a 60-watt light bulb in 5 minutes. The 2021 NIF produced 1.37 megajoules of energy in a fusion reaction, about 70% of that laser energy, the closest the world has come to a net energy gain. However, according to a report in "Nature" in July this year, American scientists later failed to replicate the record-breaking experiment in 2021, and the results of repeated attempts could only reach 50% of the energy at the end of last year. This highlights the inability of researchers to precisely understand, design and predict experiments at these energies. Earlier this year, the researchers reversed course and began rethinking their experimental design.
When the output energy and input energy of nuclear fusion reach the equilibrium point, the next step is to work towards the milestone goal of output energy being 100 times greater than the input energy. When the output energy of the fusion reaction is 100 times greater than the input energy, it is possible to explore the establishment of a commercial power station.
So even if US scientists achieve a net energy gain in fusion reactions, it doesn't mean we'll have cheap fusion energy anytime soon. According to the New York Times, the NIF's lasers are so inefficient that onceThe experiment only looked at one laser burst, while an actual fusion power plant would need the same laser burst speed as a machine gun , with each burst a new target pellet slides into place, and then the neutron stream flying out of the fusion reaction has to be converted for electrical energy. The NIF is about the size of three football fields, too big, too expensive, and too inefficient for a commercial power plant.
Technology media The Verge commented that no matter what the US government will announce on the 13th, "Even in the most optimistic scenario, any potential real-world benefits of nuclear fusion may still have to wait for more than a decade. It still seems unlikely to us." Relying on nuclear fusion energy in time to get us out of the climate crisis. But this is cool science, and people can dream.” The
Bloomberg article stated that from a scientific point of view, this progress is exciting. Researchers have been trying to make fusion power generation work since the 1950s, and every effort so far has failed. While the news is a remarkable scientific breakthrough, it has yet to take off commercially.
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