US researchers announced a historic nuclear fusion breakthrough on Tuesday, hailing a "landmark achievement" in the quest for a source of unlimited, clean power and an end to reliance on fossil fuels.

The Lawrence Livermore National Laboratory (LLNL) said it had used the world's largest laser to create, for the first time, a fusion reaction that replicated the process that powers the sun and generated more energy than it took to produce -- a goal pursued by scientists for decades.

Nuclear fusion has been touted by its supporters as a clean, abundant and safe source of energy that could eventually allow humanity to break its dependence on coal, crude oil, natural gas and other hydrocarbons driving a global climate crisis.

The US Department of Energy described the achievement of fusion ignition as a "major scientific breakthrough" that will lead to "advancements in national defense and the future of clean power."

However, there is still a long way to go before fusion is viable on an industrial scale, providing power to homes and businesses.

"There are very significant hurdles, not just in the science but in technology," Kim Budil, the LLNL director, said at a press conference.

"A few decades of research on the underlying technologies could put us in a position to build a power plant," she said.

The LLNL, which is based in California, said a team at its National Ignition Facility had achieved what is known as "net energy gain" in an experiment this month, producing more energy from fusion than the laser energy used to drive it.

"They shot a bunch of lasers at a pellet of fuel and more energy was released from that fusion ignition than the energy of the lasers," explained White House science advisor Arati Prabhakar.

- More developments needed -

For the experiment, researchers at LLNL used 192 ultra-powerful lasers to deliver 2.05 megajoules of energy to a tiny capsule smaller than a pea containing isotopes of hydrogen.

It produced 3.15 megajoules of fusion energy output.

While the result was a net energy gain, 300 megajoules of energy was needed from the electrical grid to power the lasers.

"Our calculations suggest that it's possible with a laser system at scale to achieve hundreds of megajoules of yield," Budil said.

"So there is a pathway to a target that produces enough yield, but we're very distant from that right now."

Nuclear power plants around the world currently use fission -- the splitting of a heavy atom's nucleus -- to produce energy.

Fusion on the other hand combines two light hydrogen atoms to form one heavier helium atom, releasing a large amount of energy in the process.

That's the process that occurs inside stars, including our sun.

On Earth, fusion reactions can be provoked by heating hydrogen to extreme temperatures inside specialized devices.

Like fission, fusion is carbon-free during operation, but has many more advantages: it poses no risk of nuclear disaster and produces much less radioactive waste.

Other nuclear fusion projects are also in development around the world, including the major international project known as ITER, which is currently under construction in France.

Instead of lasers, ITER will use a technique known as magnetic confinement, containing a swirling mass of fusing hydrogen plasma within a massive donut-shaped chamber.

Nuclear fusion: harnessing the power of the stars
Washington (AFP) Dec 13, 2022 - US researchers have finally surpassed an important milestone for nuclear fusion technology: getting more energy out than was put in.

The US Department of Energy announced on Tuesday that it had made a historic breakthrough with what some consider to be the energy of the future.

Here is an update on how nuclear fusion -- which produces no greenhouse gases and leaves little waste -- works, what projects are underway and estimates on when they could be completed:

- Energy of the stars -

Fusion differs from fission, the technique currently used in nuclear power plants, by fusing two atomic nuclei instead of splitting one.

In fact, fusion is the process that powers the sun.

Two light hydrogen atoms, when they collide at very high speeds, fuse together into one heavier element, helium, releasing energy in the process.

"Controlling the power source of the stars is the greatest technological challenge humanity has ever undertaken," tweeted physicist Arthur Turrell, author of "The Star Builders."

- Two distinct methods -

Producing fusion reactions on Earth is only possible by heating matter to extremely high temperatures -- over 100 million degrees Celsius (180 million Fahrenheit).

"So we have to find ways to isolate this extremely hot matter from anything that could cool it down. This is the problem of containment," Erik Lefebvre, project leader at the French Atomic Energy Commission (CEA), told AFP.

One method is to "confine" the fusion reaction with magnets.

In a huge donut-shaped reactor, light hydrogen isotopes (deuterium and tritium) are heated until they reach the state of plasma, a very low density gas.

Magnets confine the swirling plasma gas, preventing it from coming into contact with the chamber's walls, while the atoms collide and begin fusing.

This is the type of reactor used in the major international project known as ITER, currently under construction in France, as well as the Joint European Torus (JET) near Oxford, England.

A second method is inertial confinement fusion, in which high energy lasers are directed simultaneously into a thimble-sized cylinder containing the hydrogen.

This is the technique used by scientists at the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory (LLNL) in California who were behind Tuesday's announcement.

Inertial confinement is used to demonstrate the physical principles of fusion, while magnetic confinement seeks to mimic future industrial-scale reactors.

- State of research -

For decades, scientists had attempted to achieve what is known as "net energy gain" -- in which more energy is produced by the fusion reaction than it takes to activate it.

LLNL director Kim Budil cautioned that much remains to be done before it can be commercially viable.

"There are very significant hurdles, not just in the science but in technology," Budil said. "A few decades of research on the underlying technologies could put us in a position to build a power plant."

To get there, researchers must first increase the efficiency of the lasers and reproduce the experiment more frequently.

- Fusion's benefits -

The NIF's success has sparked great excitement in the scientific community, which is hoping the technology could be a game-changer for global energy production.

Unlike fission, fusion carries no risk of nuclear accidents.

"If a few lasers are missing and they don't go off at the right time, or if the confinement of the plasma by the magnetic field... is not perfect," the reaction will simply stop, Lefebvre says.

Nuclear fusion also produces much less radioactive waste than current power plants, and above all, emits no greenhouse gases.

"It is an energy source that is totally carbon-free, generates very little waste, and is intrinsically extremely safe," according to Lefebvre, who says fusion could be "a future solution for the world's energy problems."

Regardless of Tuesday's announcement, however, the technology is still a far way off from producing energy on an industrial scale, and cannot therefore be relied on as an immediate solution to the climate crisis.

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US researchers announce historic nuclear fusion breakthrough
Washington (AFP) Dec 13, 2022
US researchers announced a historic nuclear fusion breakthrough on Tuesday, hailing a "landmark achievement" in the quest for a source of unlimited, clean power and an end to reliance on fossil fuels. The Lawrence Livermore National Laboratory (LLNL) in California said an experiment it conducted this month "produced more energy from fusion than the laser energy used to drive it." The US Department of Energy described the achievement of fusion ignition as a "major scientific breakthrough" that wi ... read more