New research celebrates fusion power breakthrough, but controversy remains

On August 8, 2021, 192 laser beams pumped more energy than the entire US electric grid into a tiny gold capsule and ignited, for one second, the same thermonuclear fire that powers the Sun.

Fusion power

The fusion power 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 Letters and two published in Physical Review E — which argue that the researchers “prove that ignition, controlled nuclear fusion is achievable.” An important step to take. But definitions of what constitutes “ignition” vary, and however defined, the 2021 results are still far from a practical fusion reactor, despite producing enormous amounts 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, a process that powers stars like the Sun.

A fusion power plant would produce a lot of energy using hydrogen as fuel only from water and helium as waste, without the risk of meltdown or radiation. This is in contrast to nuclear fission, the type of reaction in contemporary nuclear power plants, which splits the nuclei of heavier 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 for generating power has eluded nuclear engineers for decades. Experiments of varied design have managed to produce fusion reactions for very small amounts of time, but never have they reached “ignition,” the point where the energy released from a fusion reaction is greater than the amount of energy required to generate and maintain that reaction.

The team at the National Ignition Facility and authors of one of three new papers, published in the journal Physical Review Letters, argue that “ignition is a state in which the fusion plasma can initiate ‘burn propagation’ into the surrounding cold fuel, which activates the potential for high energy gains. .” That is, fusion started on cold hydrogen fuel and the reaction expanded to produce much more energy than in previous experiments.

The August 8, 2021 experiment required 1.9 megajoules of energy in the form of an ultraviolet laser to stimulate a fusion reaction in a small, frozen pallet of hydrogen isotopes – an inertial confinement fusion reaction design – and released 1.3 megajoules of energy, or about 70% of the energy put into the experiment. The output, in other words, was over a quadrillion watts of power, even if released for a tiny fraction of a second.

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

Subsequent attempts to replicate the experiment produced much lower output energies, mostly in the 400 to 700 kilojoule range, leading some researchers to suggest that the National Ignition Facility’s experimental design is a technological dead-end, according to a news department report in the journal 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 prove ignition was possible using the design.

The new studies suggest that researchers are willing to keep exploring what the National Ignition Facility is capable of, especially because unlike other fusion researchers, the researchers at the facility are not primarily focused on developing fusion power plants, but better understanding thermonuclear weapons.

“We are working in a regime that no researcher has had access to since the end of nuclear testing,” Dr. Hurricane said. “This is an incredible opportunity to expand our knowledge as we continue to make progress.”

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