Nuclear Fusion News from LLNL/NIF

  • #1
Morbius
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Scientists at Lawrence Livermore National Laboratory used the NIF ( National Ignition Facility ) laser to reach encouraging progress toward ignition From "The Independent" newpaper serving Livermore:

http://www.independentnews.com/news/article_792110c0-2c5b-11e3-846e-001a4bcf887a.html [Broken]

Although not ignition, the results achieved are a major milestone on the way to achieving ignition and overall breakeven.

Dr. Gregory Greenman
 
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  • #2
Drakkith
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Huh. I thought the NIF had shut down.
 
  • #3
The cited article above reveals - Alpha Heating Demonstrated at NIF

NIF laser fusion experiments are now at a phase immediately preparatory to fusion ignition called Alpha Heating. NIF is setting new records for fusion neutron production, up by a factor of 500% since last record recorded at NIF in August 2013.

So what is Alpha Heating and why is it significant?

Alpha Heating is a fusion process where helium nuclei generated from the fusion reaction deposit enough energy to measurably increase the temperature of the fusion fuel above that produced by the laser-generated implosion. Alpha Heating is the preparatory stage right before fusion ignition.

Fusion neutron production is a measure of how much fusion is taking place.

In August 2013, NIF set a record of 3 x 10^15 neutrons for a D-T fusion shot.

In late September 2013 NIF set a record of 15 x 10^15 neutrons for a single D-T fusion shot.
(fusion as measured by neutron production is up 500% and Alpha Heating, a stage of operation right before fusion ignition, is now being demonstrated)
 
  • #4
phyzguy
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Scientists at Lawrence Livermore National Laboratory used the NIF ( National Ignition Facility ) laser to reach encouraging progress toward ignition From "The Independent" newpaper serving Livermore:

http://www.independentnews.com/news/article_792110c0-2c5b-11e3-846e-001a4bcf887a.html

Although not ignition, the results achieved are a major milestone on the way to achieving ignition and overall breakeven.

Dr. Gregory Greenman
Thanks for posting this - it sounds like significant progress. If I calculate it correctly, this represents an (Energy Out)/(Energy In) of about 2%. While this sounds a long way from break-even, we expect that the energy output will ramp up very rapidly as we approach ignition. So ignition may not be far away!
 
  • #5
phyzguy
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For what it's worth, I created the attached plot showing the recent progress NIF is making towards achieving ignition. If they can keep up this pace (a big if!) they will achieve Energy Out = Energy In in another 3-4 months. Exciting!
 

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  • #6
mheslep
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For what it's worth, I created the attached plot showing the recent progress NIF is making towards achieving ignition. If they can keep up this pace (a big if!) they will achieve Energy Out = Energy In in another 3-4 months. Exciting!
phyzguy, if you're still about, could you please share where you found the three output energy data points?
 
  • #7
phyzguy
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phyzguy, if you're still about, could you please share where you found the three output energy data points?
I just took the quoted yields (3E15 neutrons in Aug, 2013, 15E15 neutrons in Sept, 2013, and about 1E15 neutrons in Jul, 2013 from their published papers) and multiplied by 17. MeV per neutron, which is the energy output from a Dt fusion. Makes sense?
 
  • #8
Astronuc
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I just took the quoted yields (3E15 neutrons in Aug, 2013, 15E15 neutrons in Sept, 2013, and about 1E15 neutrons in Jul, 2013 from their published papers) and multiplied by 17. MeV per neutron, which is the energy output from a Dt fusion. Makes sense?
Should be about 14.1 MeV per neutron from d+t fusion. Thermal fission reactors have a fast neutron flux of about 1 e14 n/cm2/sec. One has to integrate power (W) over time to get energy. Getting the neutron energy out is good, but then there is the challenge of converting that energy to useful or usable energy, with some amount of efficiency (~33%) for a Rankine cycle without superheat.
 
  • #9
phyzguy
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Should be about 14.1 MeV per neutron from d+t fusion. Thermal fission reactors have a fast neutron flux of about 1 e14 n/cm2/sec. One has to integrate power (W) over time to get energy. Getting the neutron energy out is good, but then there is the challenge of converting that energy to useful or usable energy, with some amount of efficiency (~33%) for a Rankine cycle without superheat.
14.1 MeV is the neutron energy, but the total energy released in the DT fusion is about 17.6 MeV, 14.1 MeV in the neutron, and 3.5 MeV in the alpha. The neutrons are what is counted, but to calculate the total energy released, I believe it is valid to take the total number of neutrons released (which is what NIF reported) and multiply by 17.6 MeV. Of course to make a practical reactor, the efficiency of energy conversion needs to be considered, but the point of my original post (that mheslep asked about) was just to calculate energy out as related to energy in.
 
  • #10
Astronuc
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True, the 17.6 MeV would be per fusion reaction, and one neutron per reaction. I misunderstood the point of the neutrons. Thank you for the clarification.
 
  • #11
mheslep
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I just took the quoted yields (3E15 neutrons in Aug, 2013, 15E15 neutrons in Sept, 2013, and about 1E15 neutrons in Jul, 2013 from their published papers) and multiplied by 17. MeV per neutron, which is the energy output from a Dt fusion. Makes sense?
Thanks. Well for instance the September 2013 shot was 5e15 neutrons, not 15e15, according to this Sciencemag reference. So to which published papers do you refer?

http://news.sciencemag.org/physics/2013/10/fusion-breakthrough-nif-uh-not-really-…
 
  • #12
jimgraber
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Thanks. Well for instance the September 2013 shot was 5e15 neutrons, not 15e15, according to this Sciencemag reference. So to which published papers do you refer?

http://news.sciencemag.org/physics/2013/10/fusion-breakthrough-nif-uh-not-really-…
http://fire.pppl.gov/FPA14_NIF_Edwards.pdf This recent public presentation is not a published paper, but it gives reliable results from a scientist associated with NIF. Look at slides 4-6 for basic info about many recent shots, identified by date.
Best, jimgraber
 
  • #13
mheslep
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Thanks for the link. Any idea what the "Alpha-dominated" label means in those charts? That, at shots increasingly near ignition, the heating from generated alphas dominates the energy delivered by the beams? So, "alpha-dominated" is synonymous with ignition?
 
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  • #14
jimgraber
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I think that alpha dominated means the self heating (from alphas) exceeds the external energy input or heating. I think ignited requires that you could turn off the external heating (but of course, not the confinement) and the reaction would continue. Of course once you reach the alpha dominated point there is a positive feed back loop that will help increase self heating and help achieve ignition. Slide seven suggests that they think only a factor of two further improvement is still needed to reach ignition.

At another talk at the same conference, a JET representative indicated that they also feel they are on the edge of achieving ignition, and have a reasonable chance of reaching ignition the next time they run with DT fuel, currently planned for mid 2017.
 
  • #15
phyzguy
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Thanks. Well for instance the September 2013 shot was 5e15 neutrons, not 15e15, according to this Sciencemag reference. So to which published papers do you refer?

http://news.sciencemag.org/physics/2013/10/fusion-breakthrough-nif-uh-not-really-…
I only took the 1E15 from the published paper (Phys. Plasmas 20, 070501 (2013);) This paper actually says 8.5E14, and I'm not sure how I got to 1E15, maybe I rounded up. The 3E15 and 15E15 numbers I took from post #3 in this thread. The 15E15 came from the independent news link (http://www.independentnews.com/news/article_792110c0-2c5b-11e3-846e-001a4bcf887a.html), where Moses is quoted as saying the shot produced 15 quadrillion neutrons. Maybe they have since revised it downwards.
 
  • #16
mheslep
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I think that alpha dominated means the self heating (from alphas) exceeds the external energy input or heating. I think ignited requires that you could turn off the external heating (but of course, not the confinement) and the reaction would continue. Of course once you reach the alpha dominated point there is a positive feed back loop that will help increase self heating and help achieve ignition. Slide seven suggests that they think only a factor of two further improvement is still needed to reach ignition.


That brings up the problem of confirming "ignition" in inertial fusion, where of course there is no outer confinement. In continuous magnetic confined fusion ignition is straightforward as fusion would theoretically continue without further input. In implosion, those NIF charts suggest they will declare ignition at some level of energy release which they've modeled, a couple times higher than what they've achieved presently. Such will be a record accomplishment, yet delivered energy from the shot is in the MJ range (350 TW for ~4 ns) while the output in the hundreds of kJ range.

http://fire.pppl.gov/FPA14_NIF_Edwards.pdf
 
  • #17
jimgraber
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http://fire.pppl.gov/PHPRosen.pdf is another good reference about inertial fusion requirements. The thermal runaway mentioned on page 1693 is a key in my view. Thus, rather than ignition, "breakeven" and specially "burn fraction" are more useful measures for ICF in my view. However, the thinking seems to be that due to the thermal runaway described in the reference, once ignition is achieved, a substantial burn fraction will also be achieved, and potentially also breakeven. It is important to distinguish engineering or economic break even from scientific breakeven, which is a much weaker requirement.
 
  • #18
mheslep
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Excellent, many thanks.
 
  • #19
I read from a website: http://www.fusenet.eu/node/585

Energy supplied to the laser
(xenon lamps are powered by a capacitor bank) ----- 422 MJ
Laser Infrared output

(amplified IR light of the laser) --------------------------- 3.6 MJ
Laser Ultraviolet output

(about 50% is left after conversion to UV) ------------- 1.8 MJ
Actual energy absorbed by the DT target pellet

(In an email from NIF) -------------------------------------- 12 kJ

Energy released by fusion reactions
------------------- ~14 kJ

Just wondering, for breakeven the Energy released by fusion reactions should be at least 422 MJ (=Energy supplied to the laser), Yes? No?
One ton of TNT is about 4184 MJ, than 422MJ = 0.1 ton of TNT
Am i right?
 
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  • #20
mheslep
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Just wondering, for breakeven the Energy released by fusion reactions should be at least 422 MJ (=Energy supplied to the laser), Yes? No?
The answer depends on the definition of breakeven. Breakeven of the fusion reaction itself only requires >12 kJ. If one wishes to improve on that result then more work is needed on the fusion physics, the fuel, the beam power over time, the geometry. Breakeven for the entire system in the building requires >422 MJ, but then improvements could also be made by improving the efficiency of the laser, capacitors, optics, etc. For commercial power breakeven, something over 1 GJ is required of this system since some 2/3 of the produced energy would lost as waste heat when converted to electricity.
 
  • #21
yaakov
What are your thoughts on focus fusion using boron?Old idea pulsing flux with direct conversion of electrons to electrical power without neutrons or need for heat exchangers ,turbines etc. Eric Lerner pushing for funding few years back...
 
  • #22
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Traditional D-T fusion is hard. Proton-Boron fusion is orders of magnitude harder! Lerner et al. got some good results at modest parameters. They then extrapolated those results many orders of magnitude in order to argue that they can make the dense plasma focus work. It makes a great elevator pitch...

Extrapolations work best when they're done in small steps, or when the have strong theoretical backing. They are taking a huge leap in projecting their result to p-B relevant conditions, and the theory behind the dense plasma focus isn't well understood. In all, its not a very convincing argument. LPP is privately funded, and I wish them luck. I'll be happy if they succeed. But its a long shot.
 

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