Extract from ABC News
US scientists have made a "major scientific breakthrough" in the decades-long quest to harness fusion, the energy that powers the Sun and stars.
Key points:
- The US Energy Secretary says the discovery will "go down in the history books"
- It has been a challenging task because the fuel has to be hotter than the centre of the Sun
- Scientists say there could be ramifications for climate change and energy security
Researchers at the Lawrence Livermore National Laboratory in California for the first time produced more energy in a fusion reaction than was used to ignite it, something called net energy gain, the Energy Department said.
US Energy Secretary Jennifer Granholm said the achievement would pave the way for advances in national defence and the future of clean power.
"This is a landmark achievement for the researchers and staff at the National Ignition Facility who have dedicated their careers to seeing fusion ignition become a reality, and this milestone will undoubtedly spark even more discovery," Ms Granholm said, adding that the breakthrough "will go down in the history books".
White House science adviser Arati Prabhakar, appearing with Ms Granholm, called the fusion ignition "a tremendous example of what persistence can achieve" and "an engineering marvel beyond belief".
Proponents of fusion hope that it could one day produce nearly limitless, carbon-free energy, displacing fossil fuels and other traditional energy sources.
Producing energy that powers homes and businesses from fusion is still decades away.
But researchers said it was a significant step nonetheless.
Kim Budil, the director of Lawrence Livermore, said that science and technology hurdles meant commercialisation was probably not five or six decades away but sooner.
"With concerted effort and investment, a few decades of research on the underlying technologies could put us in a position to build a power plant," she said.
"It's almost like it's a starting gun going off," said Professor Dennis Whyte, director of the Plasma Science and Fusion Center at the Massachusetts Institute of Technology and a leader in fusion research.
"We should be pushing towards making fusion energy systems available to tackle climate change and energy security."
Net energy gain has been an elusive goal because fusion happens at such high temperatures and pressures that it is incredibly difficult to control.
How does fusion work?
Fusion works by pressing hydrogen atoms into each other with such force that they combine into helium, releasing enormous amounts of energy and heat. Unlike other nuclear reactions, it doesn't create radioactive waste.
Billions of dollars and decades of work have gone into fusion research that has produced exhilarating results — for fractions of a second.
Previously, researchers at the National Ignition Facility, the division of Lawrence Livermore where the success took place, used 192 lasers and temperatures multiple times hotter than the centre of the Sun to create an extremely brief fusion reaction.
The lasers focus an enormous amount of heat on a small metal can. The result is a superheated plasma environment where fusion may occur.
Nuclear scientists outside the lab said the achievement would be a major stepping stone, but there was much more science to be done before fusion would become commercially viable.
Riccardo Betti, a professor at the University of Rochester and expert in laser fusion, said an announcement that net energy had been gained in a fusion reaction was significant.
But he said there would be a long road ahead before the result would generate sustainable electricity.
He likened the breakthrough to when humans first learned that refining oil into gasoline and igniting it could produce an explosion.
"You still don't have the engine and you still don't have the tyres," Professor Betti said.
"You can't say that you have a car."
The net energy gain achievement applied to the fusion reaction itself, not the total amount of power it took to operate the lasers and run the project.
For fusion to be viable, it will need to produce significantly more power and for longer.
Tony Roulstone, a nuclear energy expert at the University of Cambridge, estimated that the energy output of the experiment was only 0.5 per cent of the energy that was needed to fire the lasers in the first place.
"Therefore, we can say that this result ... is a success of the science — but still a long way from providing useful, abundant, clean energy," he said.
The electricity industry cautiously welcomed the step, though emphasised that in order to carry out the energy transition, fusion should not slow down efforts on building out other alternatives like solar and wind power, battery storage and nuclear fission.
"It's the first step that says 'Yes, this is not just fantasy, this can be done, in theory,'" said Andrew Sowder, a senior technology executive at EPRI, a nonprofit energy research and development group.
It is incredibly difficult to control the physics of stars.
Professor Whyte said it had been challenging to reach this point because the fuel had to be hotter than the centre of the Sun.
The fuel does not want to stay hot — it wants to leak out and get cold. Containing it is an incredible challenge, he said.
Net energy gain isn't a huge surprise from the California lab because of progress it had already made, according to Jeremy Chittenden, a professor at Imperial College in London specialising in plasma physics.
"That doesn't take away from the fact that this is a significant milestone," he said.
It takes enormous resources and effort to advance fusion research. One approach turns hydrogen into plasma, an electrically charged gas, which is then controlled by humungous magnets.
This method is being explored in France in a collaboration among 35 countries called the International Thermonuclear Experimental Reactor as well as by researchers at the Massachusetts Institute of Technology and a private company.
Last year the teams working on those projects in two continents announced significant advancements in the vital magnets needed for their work.
AP/Reuters
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