Nuclear fusion breakthrough

  • #1
US researchers have achieved a world first in an ambitious experiment that aims to recreate the conditions at the heart of the sun and pave the way for nuclear fusion reactors.

The scientists generated more energy from fusion reactions than they put into the nuclear fuel, in a small but crucial step along the road to harnessing fusion power. The ultimate goal – to produce more energy than the whole experiment consumes – remains a long way off, but the feat has nonetheless raised hopes that after decades of setbacks, firm progress is finally being made.

Fusion energy has the potential to become a radical alternative power source, with zero carbon emissions during operation and minimal waste, but the technical difficulties in demonstrating fusion in the lab have so far proved overwhelming. While existing nuclear reactors generate energy by splitting atoms into lighter particles, fusion reactors combine light atomic nuclei into heavier particles.

In their experiments, researchers at the National Ignition Facility at the Lawrence Livermore National Laboratory in California use a bank of 192 powerful lasers to crush a minuscule amount of fuel so hard and fast that it becomes hotter than the sun.
more in,

http://www.theguardian.com/science/2014/feb/12/nuclear-fusion-breakthrough-green-energy-source
 

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  • #2
Evo
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  • #3
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The Nature article:
Fuel gain exceeding unity in an inertially confined fusion implosion
Ignition is needed to make fusion energy a viable alternative energy source, but has yet to be achieved1. A key step on the way to ignition is to have the energy generated through fusion reactions in an inertially confined fusion plasma exceed the amount of energy deposited into the deuterium–tritium fusion fuel and hotspot during the implosion process, resulting in a fuel gain greater than unity. Here we report the achievement of fusion fuel gains exceeding unity on the US National Ignition Facility using a ‘high-foot’ implosion method2, 3, which is a manipulation of the laser pulse shape in a way that reduces instability in the implosion. These experiments show an order-of-magnitude improvement in yield performance over past deuterium–tritium implosion experiments. We also see a significant contribution to the yield from α-particle self-heating and evidence for the ‘bootstrapping’ required to accelerate the deuterium–tritium fusion burn to eventually ‘run away’ and ignite.

http://www.nature.com/nature/journal/vaop/ncurrent/full/nature13008.html
ED- crossposted with evo;
anyway thread's more suited to nuclear engineering forum than CE.
 
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  • #5
berkeman
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More "sensible" coverage here as well:

http://physicsworld.com/cws/article/news/2014/feb/12/laser-fusion-passes-milestone

Please note also that this is the amount of energy created versus the amount of laser energy used. The facility itself used WAY more energy to generate these lasers than what has been generated.

Zz.
Ah, thanks Zapper. It seemed pretty strange that they had jumped all the way to energy break-even! I wish the articles would make that more clear. Even the PhysicsWorld article doesn't hilight the difference:

PhysicsWorld said:
In a paper published in Nature, Hurricane and colleagues report results from experiments carried out last September and November – the former producing 14 kJ of fusion energy from a single laser shot and the latter 17 kJ. The researchers point out that since the energy delivered to the fuel is about 10 kJ, both shots generated a fuel gain. They also calculated that as much as half of the energy output from these shots originated in alpha-particle heating. This is significant because such heating is a prerequisite for ignition.
 
  • #6
ZapperZ
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The energy delivered is from the sum of all the laser energy. So for the "system" itself, it is true that created energy is more than the input energy.

But when the goal is trying to generate an energy source, the ultimate goal is that the whole facility and process to generate energy will produce more energy than the facility consumes.

Zz.
 
  • #7
phyzguy
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More "sensible" coverage here as well:

http://physicsworld.com/cws/article/news/2014/feb/12/laser-fusion-passes-milestone

Please note also that this is the amount of energy created versus the amount of laser energy used. The facility itself used WAY more energy to generate these lasers than what has been generated.

Zz.
No, no, no! You're misinterpreting the results, and it's even worse than you think. The fusion produced more energy than the amount of energy delivered to the fuel. This is a lot less than the laser energy itself, since most of the laser energy is not absorbed by the fuel, but goes to heat up the hohlraum, ablators, etc. The energy delivered to the fuel was about 10 kJ, but the laser energy (i.e. the total energy of all of the photons in the laser beams) was about 1.5 MJ. As you said, the electrical energy input into the facility was another step larger. I don't know what it was, but the lasers can't be more than 30% efficient, so it had to be at least 5 MJ. It's a milestone, but any kind of useful energy production is clearly still a ways off.
 
  • #8
Astronuc
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No, no, no! You're misinterpreting the results, and it's even worse than you think. The fusion produced more energy than the amount of energy delivered to the fuel. This is a lot less than the laser energy itself, since most of the laser energy is not absorbed by the fuel, but goes to heat up the hohlraum, ablators, etc. The energy delivered to the fuel was about 10 kJ, but the laser energy (i.e. the total energy of all of the photons in the laser beams) was about 1.5 MJ. As you said, the electrical energy input into the facility was another step larger. I don't know what it was, but the lasers can't be more than 30% efficient, so it had to be at least 5 MJ. It's a milestone, but any kind of useful energy production is clearly still a ways off.
ZapperZ did not misinterpret the results. It is quite correct to say that "The facility itself used WAY more energy to generate these lasers than what has been generated [from fusion]." The statement does not elaborate on the various losses along the way, e.g., laser efficiency, reflection from the holdraum, etc. The article does indicate up to 26 kJ as compared to 1.8 MJ of energy delievered by the lasers. It is worse if one considers the energy put into the lasers to get the 1.8 MJ produced by the lasers.

According to the article cited, "Although the researchers have demonstrated fuel gain, it needs to be further increased by about a factor of 100 to achieve ignition." Not even close to being commercially viable.

The article also states "However, that work proved to be disappointing, leading to energy outputs about 1000 times smaller than the input."
 
  • #9
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The article also states "However, that work proved to be disappointing, leading to energy outputs about 1000 times smaller than the input."
Oh great! do you think it can be done in this century?
 
  • #10
Oh great! do you think it can be done in this century?
AFAIK, the hope is to achieve a feedback loop where fusion reactions produce enough heat to accelerate further fusion, so that a *significant fraction* of the DT reacts before fusion capsule flies apart. Thus far, only a miniscule fraction of DT reacts.

Feedback loop is an exponential process, so it may need quite a bit less than a cetury to be achieved :)
 
  • #11
Chronos
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I think we are still a ways off from any free energy lunch.
 
  • #12
analogdesign
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I think we should give the researchers in Livermore a *little* bit more credit.

The facility was designed in the late 80s and early 90s (took a long time to build) and the lasers they use are quite obsolete.

Also, the goal was to demonstrate break-even from the fuel standpoint, not overall. So they have finally achieved an important milestone for the facility.

Keep in mind as well that this is a three-pronged facility focused as well on nuclear stewardship and high-pressure science. It wasn't conceived as a facility to reach break-even from the facility standpoint.

As always, practical fusion energy is 30 years away. ;)
 
  • #13
Astronuc
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As always, practical fusion energy is 30 years away. ;)
It used to be 10 years away, about 30+ years or so ago - when I was an undergrad.
 
  • #14
analogdesign
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There must have been a recalibration to 30 years away.... 20 years ago with *I* was an undergrad. :)
 
  • #15
etudiant
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Surely the message here is that laser fusion is in desperate need of a really good idea.
Sort of like the early H bomb days, when one scientist wrote 'icicles are beginning to form' to describe the results of the bomb simulations. It was not until Ulam conceived the idea of radiation compression that the H bomb became feasible.
 
  • #16
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Surely the message here is that laser fusion is in desperate need of a really good idea.
I'm not sure I agree. Certainly a breakthrough in inertial of magnetic confinement would be nice, but I wouldn't say that they are desperate. In fact the original article linked to by the OP indicates meaningful progress. Which is not sign of desperation.

I've been following progress on NIF closely for the past couple years. For the record, I study magnetic confinement fusion but I try to keep up to date on what the inertial folks are doing. IMO opinion the biggest problem with NIF was the management during the ignition campaign. In their proposal to congress NIF set an ambitious goal of achieving ignition within three years. Early into the ignition campaign they realized that they were not on track to achieving that goal. At this point they had a choice. They could either A) perform a number of experiments to determine why they were under performing or B) apply the shot gun approach of performing a bunch of experiments trying to optimize the results. They chose the later method. Arguably, this approach would have been great if it had worked. But it didn't. And after 3 year NIF had not ignited and nobody knew why.

After that, the management of NIF changed hands. The new mangers have made it a point to understand why the NIF is under performing. They've performed a number of dedicated experiments to this end, and its working! Now some of the shots are matching the predictions and NIF is performing better in general.

A number of people pointed out the losses in the system. Modern lasers are significantly smaller, more efficient, and have higher rep rates than those used of NIF. So comparing the power into the lasers into NIF to the power from the fuel isn't the best comparison if you want to know how far off inertial fusion power is. Also the main motivation for indirect drive is that they thought it would lead to a more symmetric compression. NIF has demonstrated that this is not the case. Leading many to believe direct drive is the way to go. Direct drive would remove the hohlraum and remove another significant energy loss. Finally, I forget the exact relation but the yield scales something like the implosion velocity to the sixth power. Thus small increases in energy to the target, could lead to significant increases in fusion power.

Yes inertial fusion is still a ways away. But under the new management NIF is making progress. And there are a number of ideas on how to further improve the results. The situation is far from dire.
 
  • #17
AlephZero
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Oh great! do you think it can be done in this century?
Well, there's a sign behind the bar in my local pub that says "free beer tomorrow". And the sign has been there since the previous century....

I remember the first time I heard in a school science lesson (in elementary school) that fusion was going to solve all the world's energy problems. That was http://en.wikipedia.org/wiki/ZETA_(fusion_reactor). This doesn't seem to be a topic where concepts like "on time and within budget" apply.
 
  • #18
etudiant
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I'm not sure I agree.

Yes inertial fusion is still a ways away. But under the new management NIF is making progress. And there are a number of ideas on how to further improve the results. The situation is far from dire.
Thanks for an insightful update. You make a good case that the NIF is still making progress.
That said, your report makes it evident that this approach is not a royal road to fusion either, but also a trench warfare style struggle to improve painfully insufficient results by eliminating more of the many obstacles that nature puts in our way, with no real assurance that the path will lead to success.
 
  • #19
berkeman
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So with all the discouraging news about ICF in this thread, how is magnetic confinement doing?
 
  • #21
Astronuc
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