Energy

Scientists announce breakthrough in quest for fusion power

A metallic case called a hohlraum holds the fuel capsule for the NIF experiments (Photo: Eduard Dewald/LLNL)
A metallic case called a hohlraum holds the fuel capsule for the NIF experiments (Photo: Eduard Dewald/LLNL)
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A metallic case called a hohlraum holds the fuel capsule for the NIF experiments (Photo: Eduard Dewald/LLNL)
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A metallic case called a hohlraum holds the fuel capsule for the NIF experiments (Photo: Eduard Dewald/LLNL)
Mock up of a hohlraum used to hold the plastic capsule (Image: Lawrence livermore)
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Mock up of a hohlraum used to hold the plastic capsule (Image: Lawrence livermore)

In a perfect example of beating swords into plowshares, a team of scientists at the Lawrence Livermore National Laboratory's (LLNL) National Ignition Facility (NIF) in California reached a milestone in the quest for practical fusion power using a process designed for the development and testing of nuclear weapons. The announcement in the February 12 issue of Nature claims that the team used the world’s most powerful laser barrage to produce a controlled fusion reaction where more energy was extracted from the fuel than was put into it.

If there is an ultimate engineering dream, then nuclear fusion is about as close as close as one can get. By literally harnessing the power of the stars, it holds the promise of what is, for all practical purposes, unlimited clean energy. Since man-made fusion was first demonstrated in 1951 with a boosted fission weapon, scientists and engineers have worked on some way to produce a practical fusion reactor instead of a hydrogen bomb.

The story of the fusion reactor is one of both great progress, but also constant frustration. When work began, the first reactor was predicted to be 25 years away. Since then and up until today, it’s still 25 years away. That’s because although nuclear fusion is relatively simple in theory, getting a controlled reaction started outside of the heart of a star is extremely difficult. The trick is to reach the “ignition” point, where the energy released by the reactor is greater than what’s put into it and the reaction becomes self-sustaining.

A fusion reactor works by simulating the conditions inside the Sun. Put simply, hydrogen atoms fuse in the Sun because its huge mass squashes the atoms together to form helium, releasing huge amounts of energy as the strong nuclear force that keeps them apart is overcome. A hydrogen bomb does the same thing, only with a fission bomb creating the necessary conditions for a millionth of a second.

Mock up of a hohlraum used to hold the plastic capsule (Image: Lawrence livermore)
Mock up of a hohlraum used to hold the plastic capsule (Image: Lawrence livermore)

A fusion reactor creates the right pressures and temperatures by taking an ionized plasma of the hydrogen isotopes deuterium or tritium and squeezing it using magnetic fields or lasers to set off the reaction. Not surprisingly, this requires huge amounts of energy, which set off various processes that heat the plasma to incredible temperatures.

The NIF breakthrough isn’t ignition, but it is a significant waypoint. The NIF team achieved what is called a “fuel gain”. Using an array of 192 high-energy lasers aimed at one tiny plastic sphere filled with a mixture of deuterium and tritium, the scientists subjected the droplet of cryogenic fuel to 1.9 megajoules of light to produce sun-like temperatures for a tiny fraction of a second. The result was a fusion reaction where the energy put into the fuel was exceeded by the energy that came back out – something that until now has never been achieved anywhere outside of a star or a hydrogen bomb, and is ten times greater than anything previously seen. The key to this is something called "boot-strapping".

Boot-strapping works by using alpha particles, which are helium atoms stripped of their electrons. Normally, when a fusion reaction produces such particles, they shoot off, carrying energy with them. In bootstrapping, the deuterium/tritium mixture is made to capture the alpha particles, which heats the plasma more and releases more alpha particles to increase the reaction.

According to the team, the key to boot-strapping was to keep the plastic shell that contains the fuel from disintegrating during compression under a high-energy laser pulse by altering the timing of the pulse to "fluff up" the ablative plastic, making it more resilient. The team believes that this disintegration in previous tests hindered the reaction and by modifying the laser they were able to prevent this.

"What's really exciting is that we are seeing a steadily increasing contribution to the yield coming from the bootstrapping process we call alpha-particle self-heating as we push the implosion a little harder each time,” says Omar Hurricane, lead author of the team’s report.

Ironically, power generation wasn’t the team’s primary goal. The NIF is designed to provide hard data for computer models that simulate the explosion of a nuclear warhead as part of the US program to produce new warheads and to ensure that the existing stockpiles remain safe and reliable. Up until the comprehensive nuclear test ban treaty, this would have been done using underground test explosions, but the US government now relies on lasers and supercomputers for the National Nuclear Security Administration's Stockpile Stewardship Program.

Eventually, the scientists hope the boot-strapping process will lead to ignition, but that remains in the future, as does practical application in a working commercial reactor. Currently, the experiment is only able to produce of net gain of about one percent. "There is more work to do and physics problems that need to be addressed before we get to the end," said Hurricane, "but our team is working to address all the challenges, and that's what a scientific team thrives on".

The team’s results were published in the journal Nature.

Source: Lawrence Livermore National Laboratory

25 comments
Joseph Kitchin
Wait, they got a positive Q value? that in and of itself is HUGE, even if the net gain is small....however, one percent of how much juice NIF uses per shot is actually a decent chunk of kilowatts. never heard of this alpha-capture method before, although its probably a technique specific to inertial confinement fusion, meaning it wont be useful for torroidal fusion or fusor designs or anything
Anne Ominous
HUGE QUALIFIER: They achieved gain, but NOT "net" gain. The target released more energy than was put into it by the lasers. It must be said that is an awesome achievement. BUT, the energy *that powered the lasers* was greater than the energy they got out. So there was not an actual net gain. It took more energy, overall, to create the fusion than it released. But this is a major milestone, no doubt about it.
Mel Tisdale
At the end of the Monty Python Spanish Inquisition programme, the cardinals are seen rushing to yet another opportunity to utter the immortal words: "No one expects the Spanish Inquisition!" The closing credits roll while they are en route and the programme eventually comes to a close just as they arrive at their destination. The words "Oh ******!" can be heard in the background. Fusion energy production, be it hot, or even cold, reminds me of that sketch. If, or perhaps more optimistically, when, it arrives I think it will be too late. We desperately need a new supply of cheap, i.e. easy to extract, oil, not just electricity, and we need it yesterday. It is nice to know that milestones are being passed, albeit oh so slowly. I just hope that when the technology arrives as a working process, exuding all shiny newness and capable of producing copious amounts of cheap energy, the scientists will not be heard repeating the "Oh ******!" expression.
Mariusz Gyan
People There have been hundreds of experiments where fusion has been achieved in low temperatures (and small devices). And energy gain is about 300%. Some technologies are going to production lines.
ErinTarn
Sadly even if ignition is achieved and becomes practical, the average person will never see the benefit because it would mean the literal end to rationing energy by way of monetary payment. In other words, as long as there is a profit to be made, true advancedment will be stymied. The same can be applied to cancer cures, teleportation, advanced space travel, etc. Greed overcomes all.
Mzungu_Mkubwa
"as part of the US program to produce new warheads and to ensure that the existing stockpiles remain safe and reliable." Sorry, had to LOL at the irony of this statement when I read it. Warheads safe? And reliable? Aren't those two goals in direct conflict with one another? ☺
Neil Farbstein
It took a facility bigger than a football field to confine alpha particles to a fusion pellet long enough to get past breakeven. Inertial confinement fusion is going to look like big dinosaur when commenting technology l;tike low energy nuclear fusion reaction reactors come on the scene. Vulvox has an aneurtronic fusion reactor on the drawing board that will cost hundreds of times less than laser ICF reactors or the biggest dinosaur of them all- the ITER tokamak type reactors. We also have a performance materials program for developing materials that can be used in clean aneutronic LENR reactors. http://vulvox.tripod.com/id10.html
piperTom
From above: "[A star's] huge mass squashes the atoms together to form helium, releasing huge amounts of energy as the strong nuclear force that keeps them apart is overcome." No; and again, no. The stars mass provides a high density, where the high temperature will, occasionally, provoke a collision so direct and violent as to overcome the electric force ... or close enough for the strong nuclear force to come into play. The strong nuclear force is *used* not "overcome". And PLEASE don't use the adverb "literally" to describe "harnessing". There are no horses in evidence.
moreover
A welcome step forward. But there remains the frustration that commercialization always seems 25 in the future… By contrast, a US conversion to renewable energy would cost an estimated $26b/yr versus $120b/yr for the hidden costs of fossil fuels in the US PLUS $271 billion/yr. projected damage by climate change impacts (Ackerman & Stanton, Tufts U, 2008); (US Acad. of Sciences, 2010). NREL's Chuck Kutscher makes that case at the 1 hour mark in a Jan 26 2014 talk: Climate Change: The Latest Findings and What We Must Do. http://prairiefirenewspaper.com/2014-winter-lecture-series-january-26
Nelson Hyde Chick
Our discovery of an inexhaustible, cheap, nonpolluting energy source will save humanity from itself but not all other life on this planet from humanity.