The breakthrough in fusion power is celebrated in new studies, but the controversy continues

The breakthrough in fusion power is celebrated in new studies, but the controversy continues

On August 8, 2021, 192 laser beams pumped far more power than the entire US power grid into a tiny golden capsule and ignited, for a fraction of a second, the same thermonuclear fire that powers the Sun.

The fusion energy experiment, conducted by the National Ignition Facility at Lawrence Livermore National Laboratory in California, is explored in detail in three new papers, one published in Physical review lettersand two articles published in Physical review E – who argue that the researchers achieved “ignition”, a crucial step that shows that controlled nuclear fusion is possible. But definitions of what constitutes “ignition” vary, and however defined, the 2021 results are still a long way from a practical fusion reactor, despite producing a very large amount of energy.

Nuclear fusion involves the fusion of two elements, usually isotopes of hydrogen, into the heavier element helium. It releases enormous amounts of energy in the process, which is the process that powers stars like the Sun.

A fusion power plant would produce abundant energy using only hydrogen from water as fuel, and producing helium as waste, with no risk of fusion or radiation. This is in contrast to nuclear fission, the type of reaction in modern nuclear power plants, which splits the nuclei of heavy elements such as uranium to produce energy.

While fusion reactions take place in the Sun, and uncontrolled fusion takes place in thermonuclear weapon explosions, controlling a sustained fusion reaction to generate energy has eluded nuclear engineers for decades. Experiments of various designs have long succeeded in producing fusion reactions, but they have never reached “ignition,” the point where the energy released from a fusion reaction is greater than the amount of energy needed to generate and maintain this reaction. .

The National Ignition Facility team and authors of one of the three new articles, published in the journal Physical review letters, argue that “ignition is a state where the fusion plasma can begin to ‘spread’ into the surrounding cold fuel, allowing the possibility of a large energy gain.” That is, fusion began in the cold hydrogen fuel and the reaction expanded to generate much more energy than in previous experiments.

The August 8, 2021 experiment required 1.9 megajoules of energy in the form of ultraviolet lasers to instigate a fusion reaction in a small frozen pellet of hydrogen isotopes, a confinement fusion reaction design inertial, and released 1.3 megajoules of energy, or about 70% of the energy input to the experiment. The output, in other words, was more than a quadrillion watts of power, even if it was only released for a tiny fraction of a second.

“The record shot was an important scientific advance in fusion research, establishing that fusion ignition in the laboratory is possible at NIF,” said Omar Hurricane, chief scientist of the Inertial Confinement Fusion Program at NIF. Lawrence Livermore National Laboratory, in a statement. “Achieving the necessary conditions for ignition has been a long-standing goal for all inertial confinement fusion research and opens access to a new experimental regime where alpha particle self-heating overcomes all cooling mechanisms of the fusion plasma”.

Subsequent attempts to replicate the experiment have produced much lower energy outputs, mostly in the 400 to 700 kilojoules range, leading some researchers to suggest that the National Ignition Facility’s experimental design is a dead end technique, as reported by the news department. in the newspaper Nature.

“I think they should call it a success and stop,” said physicist and former US Naval Research Laboratory laser fusion researcher Stephen Bodner. Nature.

The National Ignition Facility cost $3.5 billion, more than $2 billion more than expected, and is behind schedule, with researchers initially targeting 2012 as the deadline to demonstrate that the ignition was possible by design.

The new studies suggest that researchers are ready to continue exploring what the National Ignition Facility is capable of, especially since, unlike other fusion researchers, the facility’s researchers are not primarily focused on developing fusion power plants , but to better understand thermonuclear weapons.

“We are operating in a regime that no researcher has accessed since the end of nuclear testing,” Dr Hurricane said. “It’s an incredible opportunity to expand our knowledge as we continue to move forward.”

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