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Carbon-free fusion power could be ‘on the grid in 15 years’

Discofan said:
I am not surprised. The other day I saw that they were doing something with fart gas. They tried to burn two mannequins in a tent with their own (simulated) fart gas, assuming that they've been farting for hours and that someone lit a match...
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To this day my favourite mythbusters episode was the shattering CD episode where they spun CDs and shattered them, the slow motion footage was cool.

The episode came about because of stories on the internet of optical drives in computers spinning so fast the disks inside exploded.
 
Tetragrammaton Invictus said:
To this day my favourite mythbusters episode was the shattering CD episode where they spun CDs and shattered them, the slow motion footage was cool.

The episode came about because of stories on the internet of optical drives in computers spinning so fast the disks inside exploded.
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Did you watch the movie "Mission To Mars"? In it, an astronaut spins so fast that his body explodes. I guess you must spin much faster to break a CD.
 
Discofan said:
Did you watch the movie "Mission To Mars"? In it, an astronaut spins so fast that his body explodes. I guess you must spin much faster to break a CD.
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YES......... I have a soft spot for that movie. The sand tornado yeah, ripped the guy to bits. But hey it's a movie.
 
https://www.wired.com/2015/03/happens-cd-spins-fast/

It's easy to wok out the acceleration acting on the edge of a CD spinning at 23,000 rpm. It's radius times the square of the angular velocity, so 0.006 metres x (2408 radians per second)^2 = 348,068 ms^-2 or 35,481 times the acceleration due to gravity on the Earth's surface (9.81ms^-2).

From cadaver studies, a force of at least 30kN is required to tear off a human arm (that's equivalent to hanging a mass of about 3 metric tonnes off the arm in Earth's gravity). An average human arm has a mass of 4kg so, assuming a radius of spin of 0.25m at the shoulder, the spin required to remove an arm would be sqrt(force/(mass*radius)) = sqrt(30,000/1) = 173 radians per second = 27 revolutions per second or 1,620 rpm. At the shoulder joint, the acceleration would be 765 times that due to earth's gravity.
 
I doubt Lockheed Martin are now in the business of selling snake oil so it sounds promising. I'd be fascinated to learn about the configuration of the magnetic confinement, how electrical energy is extracted, and how the problems of neutron damage and activation are dealt with.
 
Asbo Zaprudder said:
I doubt Lockheed Martin are now in the business of selling snake oil so it sounds promising. I'd be fascinated to learn about the configuration of the magnetic confinement, how electrical energy is extracted, and how the problems of neutron damage and activation are dealt with.
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It does look like their design changed somewhat from the initial one they showed off a few years ago. It they went aneutronic, maybe they're going for direct electrical conversion? They'd have to hit some incredibly high temps for that, but if anyone could do that, they could. the Lawrenceville Plasma Physics group reached an equvalent of 2.5 billion C late last year, and I believe TAE is hitting some high numbers as well. It looks like a bit of a race between Helion, Lockheed, TAE, and LPP to hit breakeven in the next 2-3 years. Could happen earlier. Just how game changing that is for the world isn't really understood, and discussing it sounds like hyperbole, but once it's reached, we start to become a post-scarcity species. It takes awhile to realize the implementation of it.

MANT! said:
Ever since I was a child Fusion energy has been 15 or 20 years away... I'm not holding my breath..
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There seems to be a Godwin's Law that this must be restated in any discussion involving fusion.
 
In D-T fusion, 80% of the energy goes into the kinetic energy of the neutrons produced, which cause structural damage and produce radioactive byproducts by activation and can leak out of the reactor's confinement even if moderated.

Pondering how aneuronic energy conversion might work, I can only think that it uses something like isotope Boron-10 in Boron Trifluoride gas to capture a thermalised neutron and split into Helium-4 and Lithium-7 charged nuclei, whose kinetic energy can potentially be extracted and converted to electrical energy using MHD techniques. There would also be a thermal energy byproduct but a standard Brayton cycle could be used for that (also direct heat to magnetism conversion is a possibility if the efficiency could be improved).

https://en.m.wikipedia.org/wiki/Thermo-magnetic_motor

For the future, He-3-based fusion would reduce but not entirely eliminate the neutron problem.
 
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Asbo Zaprudder said:
In D-T fusion, 80% of the energy goes into the kinetic energy of the neutrons produced, which cause structural damage and produce radioactive byproducts by activation and can leak out of the reactor's confinement even if moderated.

Pondering how aneuronic energy conversion might work, I can only think that it uses something like isotope Boron-10 in Boron Trifluoride gas to capture a thermalised neutron and split into Helium-4 and Lithium-7 charged nuclei, whose kinetic energy can potentially be extracted and converted to electrical energy using MHD techniques. There would also be a thermal energy byproduct but a standard Brayton cycle could be used for that (also direct heat to magnetism conversion is a possibility if the efficiency could be improved).

https://en.m.wikipedia.org/wiki/Thermo-magnetic_motor

For the future, He-3-based fusion would reduce but not entirely eliminate the neutron problem.
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1p + 11B → 3*4He + 8.7 MeV

so using Boron 11 gives Helium ions and creates a relatively benign environment around the reactor. That level of energy is too high for current electrostatic devices, in any kind of potential reactor (I guess?!) but there are methods like you mentioned, or a travelling wave guide converter. Obviously there are some losses in any system.
 
also added: the world is running out of easily obtained helium. these aneutronic reactors would actually produce a very useful byproduct.
 
XCV330 said:
1p + 11B → 3*4He + 8.7 MeV

so using Boron 11 gives Helium ions and creates a relatively benign environment around the reactor. That level of energy is too high for current electrostatic devices, in any kind of potential reactor (I guess?!) but there are methods like you mentioned, or a travelling wave guide converter. Obviously there are some losses in any system.
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It seems you're expecting to use Boron-11 in the reactor itself. The energy required is 675 keV for the lowest resonance capture energy with a high cross-section as compared to100 MeV for D-T so the input power requirement is much greater. It does have the advantage of removing the neutrons altogether although there might well be neutrons produced from p-He-4 interactions I expect. Electrical power is directly obtainable in this scheme.

http://www.iaea.org/inis/collection/NCLCollectionStore/_Public/24/028/24028563.pdf

My proposal for using Boron-10 would be to place it externally to the reactor behind a moderating blanket of a plastic such as polypropylene or similar that would thermalise the neutrons to about 0.025 MeV; the thermal energy could be extracted using a Brayton cycle. The kinetic energy of the Helium and Lithium ions would be directly converted or the Brayton cycle used.

The cross-section for Boron-10 is much higher than for Boron-11, which is why it was used in neutron detectors in preference to Boron-11, for example, Boron Trifluoride proportional counters.

n + B-10 → He-4 + Li-7 (2.79 MeV) with 6% probabilty
or
n + B-10 → He-4 + Li-7 (2.31MeV) + γ (0.48MeV) with 94% probability

Potentially the energy of 0.48 MeV gamma ray is directly convertible but using the Brayton cycle might be simpler.
 
Asbo Zaprudder said:
It seems you're expecting to use Boron-11 in the reactor itself. The energy required is 675 keV for the lowest resonance capture energy with a high cross-section as compared to100 MeV for D-T so the input power requirement is much greater. It does have the advantage of removing the neutrons altogether although there might well be neutrons produced from p-He-4 interactions I expect. Electrical power is directly obtainable in this scheme.

http://www.iaea.org/inis/collection/NCLCollectionStore/_Public/24/028/24028563.pdf

My proposal for using Boron-10 would be to place it externally to the reactor behind a moderating blanket of a plastic such as polypropylene or similar that would thermalise the neutrons to about 0.025 MeV; the thermal energy could be extracted using a Brayton cycle. The kinetic energy of the Helium and Lithium ions would be directly converted or the Brayton cycle used.

The cross-section for Boron-10 is much higher than for Boron-11, which is why it was used in neutron detectors in preference to Boron-11, for example, Boron Trifluoride proportional counters.

n + B-10 → He-4 + Li-7 (2.79 MeV) with 6% probabilty
or
n + B-10 → He-4 + Li-7 (2.31MeV) + γ (0.48MeV) with 94% probability

Potentially the energy of 0.48 MeV gamma ray is directly convertible but using the Brayton cycle might be simpler.
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I will go out on a limb here, understanding I am out of my comfort level, but 675keV is peak resonance and not necessarily needed for every aneutronic fusion method (I know, if it was easy we'd have one now) but Bussard's idea was to keep the plasma confined with much smaller initial energy using plasma in polywell configuration. The latter part has been demonstrated, though I do not understand why that work is not being followed up on more vigorously.

I like your idea. it's elegant. But polyprop melts at around 400K (and turns into a wickedly nice rocket fuel at high temp with the right oxidizer). would your sheet get that hot?
 
XCV330 said:
I will go out on a limb here, understanding I am out of my comfort level, but 675keV is peak resonance and not necessarily needed for every aneutronic fusion method (I know, if it was easy we'd have one now) but Bussard's idea was to keep the plasma confined with much smaller initial energy using plasma in polywell configuration. The latter part has been demonstrated, though I do not understand why that work is not being followed up on more vigorously.

I like your idea. it's elegant. But polyprop melts at around 400K (and turns into a wickedly nice rocket fuel at high temp with the right oxidizer). would your sheet get that hot?
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I assume the reactor vessel is actively cooled and energy extracted via a Brayton cycle. The coolant, probably water, would also act as a neutron moderator in its own right so perhaps the additional moderator isn't required. Graphite might be usable in place of plastic if the thermal environment is a problem but protons are more efficient at thermalising neutrons than carbon nuclei.
 
We're in the Biff Tannen dystopian future. Flying cars were either never invented or killed by the oil interests (as the technology ran on trash).
 
Snaploud said:
We're in the Biff Tannen dystopian future. Flying cars were either never invented or killed by the oil interests (as the technology ran on trash).
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That's too bad, considering the billions of tons of trash that we've poured in the oceans already...
 
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