US scientists have achieved the first energy gain in a fusion reaction, the country’s Energy Secretary Jennifer Granholm has confirmed, heralding the breakthrough as proof that the technology could eventually provide an abundant and carbon free to fossil fuels.

“It’s a historic achievement,” Granholm said at a news conference in Washington on Tuesday, confirming the breakthrough first reported by the Financial Times.

“We have taken the first steps towards a clean energy source that could revolutionize the world,” said Jill Hruby, administrator of the National Nuclear Security Administration.

But how close does this breakthrough bring the energy sector to the fusion power dream?

What is Merger?

Fusion is the reaction that powers the sun. It involves heating two isotopes of hydrogen – normally deuterium and tritium – to such extreme temperatures that the atomic nuclei fuse, releasing helium and large amounts of energy in the form of neutrons.

Unlike nuclear fission, the process produces no long-lived radioactive waste. It also emits no carbon, and scientists estimate that a small cup of fuel could power a home for over 800 years.

Fusion proponents describe it as the “holy grail” of clean energy: a technology that could theoretically provide nearly limitless, carbon-free energy.

But although Soviet scientists developed the first fusion machine in the 1950s using a process called magnetic confinement, until now no group had been able to produce more energy from a reaction of fusion than it consumed – a scientific step known in the field as scientific energy gain or target gain.

What have American scientists achieved?

Scientists at the US government’s National Ignition Facility at Lawrence Livermore National Laboratory in California have achieved this goal of energy gain in the reaction for the first time.

The $3.5 billion NIF, which opened in 2009, was primarily designed to test nuclear weapons by simulating explosions, but has also been used to advance fusion energy research.

Magnetic confinement, which remains the most studied fusion approach, uses huge magnets to hold deuterium-tritium fuel in place while it is heated to temperatures hotter than the sun.

The NIF uses a different process, called inertial confinement, in which it fires 192 lasers at a tiny fuel capsule. The lasers heat the fuel to more than 3 minutes Celsius, which blasts across the surface of the target capsule, causing what the NIF describes as a “rocket-like” implosion. This further compresses and heats the fuel until the hydrogen atoms of deuterium and tritium fuse together, releasing helium and energy.

In the Dec. 5 experiment, the reaction produced about 3.15 megajoules of energy, or about 150 percent of the lasers’ 2.05 MJ of energy, the lab said Tuesday. The gain was even bigger than the preliminary results reported by the FT.

Does that mean they have cracked fusion power?

No. Energy gain has been seen for decades as a crucial step in proving that commercial fusion power plants are possible. However, there are still several hurdles to overcome.

First, the energy gain in this context only compares the outgoing energy to the energy in the lasers, not to the total amount of energy drawn from the array to power the system. In fact, each shot requires 330 MJ of electrical energy, delivered in a burst of 400 microseconds.

The system that powers the NIF lasers is old and not designed for maximum energy efficiency. However, scientists still estimate that commercial fusion will require fusion reactions that generate between 30 and 100 times the incoming energy.

The NIF also fires a maximum of one shot per day, whereas an internal containment plant would probably have to fire several shots per second.

“The experiment unambiguously demonstrates that the physics of laser fusion works,” said Robbie Scott, a plasma physicist who contributed to the NIF research. “Next steps include demonstrating an even higher fusion energy gain and developing more efficient methods to drive the implosion.”

How does it compare to other recent breakthroughs?

The achievement at NIF follows big announcements over the past 18 months by other publicly funded fusion labs with slightly different research goals.

Last year in China, a magnetic confinement machine, known as a tokamak, called East – the Experimental Advanced Superconducting Tokamak – managed to sustain a fusion reaction at 120 mnC for a record 101 seconds. Temperatures above 100mnC, generally required for fusion by magnetic confinement, had already been reached but never maintained for such a long time.

In May, researchers of the world’s largest and most powerful tokamak in Oxford, the Joint European Torus (JET), produced a record 59 MJ from a five-second sustained reaction. That was enough energy to boil around 60 kettles and more than double the previous energy production record of 22 MJ, achieved by JET in 1997.

Neither reaction demonstrated an energy gain the way NIF did, but neither facility prioritized obtaining a gain, the experts said.

What happens next?

The industry hopes this breakthrough will galvanize interest and investment and thus accelerate progress.

Historically, most fusion science has been carried out by publicly funded laboratories such as NIF and JET, but in recent years investment has also flowed into private companies promising to provide fusion energy in the 2030s.

Melanie Windridge, a plasma physicist who runs consultancy Fusion Energy Insights, pointed out that the NIF, which cost $3.5 billion to build, was 13 years old and based on laser technology developed in the 1980s. .

“If you can do it with aging technology, it just shows what could be possible with the newest equipment,” she said. “If they get private support and they’re able to move in those aggressive timelines, they can use advanced technology. . . and it is extremely exciting.