Nuclear fusion “breakthrough” is super hot science, but… • The Register

Scientists at Lawrence Livermore National Laboratory (LLNL) have achieved fusion ignition in a nuclear reactor, it was announced Tuesday.

The dream of generating relatively clean, fusion-based electricity has been pursued for decades. Now the US Department of Energy and LLNL believe they are a significant step closer to that goal, confirming previous reports.

On Tuesday this week, during a livestream broadcast, officials presented the results of an experiment conducted on Dec. 5 at the lab’s National Ignition Facility (NIF).

The inventors said they produced 3.15 megajoules of fusion energy as an output, surpassing the 2.05 megajoules delivered by the 192 lasers that started the nuclear fusion reaction. In other words, LLNL achieved fusion ignition inside a reactor and got (in a way) more energy out of the reaction than it put into it (though more on that later). It’s a milestone for the team and, according to the Americans, a unique achievement.

You can replay the announcement below.

Youtube video

“The quest for fusion ignition in the laboratory is one of the greatest scientific challenges humankind has ever faced, and the achievement of this goal is a triumph of science, technology, and most importantly, people,” said Kim Budil, Director of LLNL statement.

“Crossing that threshold is the vision that has driven 60 years of dedicated pursuit – a continuous process of learning, building, expanding knowledge and skills, and then finding ways to meet the challenges that have arisen.”

Meanwhile, US Energy Secretary Jennifer Granholm called the results “a landmark achievement,” while senators and congressional officials also gushed about the “major scientific breakthrough.”

The NIF works by firing nearly 200 lasers to shine beams of ultraviolet energy at a tiny pellet of fusion fuel held in a cavity. This energy is converted into X-rays, which crush and implode the pellet. The pea-sized capsule then turns into a super-hot, high-pressure plasma that provides the right conditions for its atoms of deuterium and tritium to fuse.

cavity 121322 The cavity housing the type of cryogenic target used for ignition on December 5, 2022 at LLNL's National Ignition Facility

Where the magic happens… The cavity containing the pellet of fusion fuel, a frozen mixture of hydrogen isotopes

This nuclear fusion reaction forms helium nuclei and neutrons. In theory, relatively clean electricity can be used, for example by converting the energy of the neutrons into heat, to drive a steam turbine and generate electricity. It’s not too different from the mechanics of a thermonuclear weapon or a star, where deuterium and tritium fuse together under incredible pressure.

Last year, the LLNL said its researchers are on the verge of achieving fusion ignition. This time, however, the team managed to extract more energy than the laser energy used to burn the cryogenic fuel pellet.

“The laser team recently completed an upgrade to increase the energy delivered by eight percent,” said Alex Zylstra, a lead experimenter at LLNL The registry.

“We then came up with a modified design that uses this extra energy to implode thicker fuel pellets, resulting in higher power, with fusion power exceeding laser energy.”

The target chamber of LLNL's National Ignition Facility where 192 laser beams delivered more than 2 million joules of ultraviolet energy to a tiny fuel pellet to create fusion ignition on December 5, 2022

Medium machine… target chamber of the LLNL’s National Ignition Facility where a fusion fuel pellet was ignited in early December. Source: LLNL

While the results are worth celebrating, they show that fusion is very, very far from being a practical source of energy. The initial energy required to fire the laser beams was 322 megajoules, with just over 2 megajoules delivered to the fuel capsule to trigger its implosion.

When compared to the 3.15 megajoules produced in the nuclear reaction, the total energy produced by the NIF is still a net loss by quite a factor.

We note that the LLNL NIF is also not exclusively focused on clean power generation, instead focusing on nuclear weapon simulations.

Zylstra said details of the experiment will be reported in an upcoming article to be submitted to a journal for peer review. “These results open the door to conducting experiments under conditions that could never before be achieved in the laboratory. By increasing our understanding of these fusion plasmas, we will work towards generating even higher fusion power and explore conditions relevant to the Nuclear Weapons Stewardship mission,” he told us.

The DoE noted that “many advanced scientific and technological developments are still required to provide simple, affordable… [ignition fusion energy] (IFE) to power homes and businesses” and is keen to restart a “coordinated IFE program” with the private sector. Zylstra agreed, saying that reactors need to achieve higher power gains at faster rates in nuclear fusion power reactors to be commercially viable in the future. ®

https://www.theregister.com/2022/12/14/nuclear_fusion_doe/ Nuclear fusion “breakthrough” is super hot science, but… • The Register

Rick Schindler

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