Or- comparing apples and apples...
If the Polywell can fuse deuterium- tritium (but not any other fuel) at high enough efficiency to make a power producing reactor- like a Tokamak, how would it compare to a Tokemak in size and cost. The x-ray problems, and drive conditions would be eased compared to D-D fusion or any other fuel. Size could presumably be smaller.
The biggest question that comes to mind is the neutron flux. The magrids would be closer to the fusion plasma, so it would be exposed to higher fluxes compared to the magnets in a commercial Tokamak (which are also shielded by the proposed lithium blanket). I'm assuming the neutron flux would be twice as great as the D-D reaction, and possibly more important, each neutron would be ~ 4 times as energetic,Would the neutron flux on the magrid be intolerable? Given sufficiant construction cost advantages over the Tokamak, would the maintainance/ replacement costs for the magrids still allow for lower lifetime costs (sort of like the 'Riggatron' that Dr. Bussard played with ~1980- in which the magnets were within the vacuum vessel and were predicted to need replacement/ reprocessing every 6 months)?
I wildly speculate that providing a lithium blanket outside of a Polywell for tritium production would be easier and less challenging than providing one inside a Tokamak.
Dan Tibbets
Polywell vs Tokamak- using Deuterium and Tritium fuel
Polywell vs Tokamak- using Deuterium and Tritium fuel
To error is human... and I'm very human.
Re: Polywell vs Tokamak- using Deuterium and Tritium fuel
Look at Figure 65 of this report. Says ~ 30x smaller.D Tibbets wrote:Or- comparing apples and apples...
If the Polywell can fuse deuterium- tritium (but not any other fuel) at high enough efficiency to make a power producing reactor- like a Tokamak, how would it compare to a Tokemak in size and cost. The x-ray problems, and drive conditions would be eased compared to D-D fusion or any other fuel. Size could presumably be smaller.
http://www.askmar.com/Fusion_files/EMC2 ... plants.pdf
Figure 66 also relates. Great report, though old.
Edit:
Deleted a total misreading of the question and article.
Sometimes we see what we expected to see not what is really there.
Sorry.
I was reading how much smaller would a Polywell reactor be if designed for DD or DT instead of PB.
Deleted a total misreading of the question and article.
Sometimes we see what we expected to see not what is really there.
Sorry.
I was reading how much smaller would a Polywell reactor be if designed for DD or DT instead of PB.
Last edited by tombo on Sun Jan 04, 2009 11:18 pm, edited 2 times in total.
I would think 30X smaller than a Tokamak. 30X is about a factor of 27,000 difference in volume which mirrors Rick Nebel's estimate of a 60,000X increase in density.tombo wrote:30x smaller than a 1.6m radius WB100 is about 100mm diameter. (That's 4 inches.)
Did I do that right?
This is in the range of existing equipment.
Does this suggest an experiment to anyone?
Of course, there is the problem of needing a really big pile of spare concrete blocks.
Personally I'd go with pumped lithium cooling (for tritium generation) and MgB11 superconductors which would improve neutron resistance.
However I think a D-D reactor would be better (even with the smaller gain) as it would ease the fuel problem of T generation. The neutron flux wouldn't be much different (within an order of magnitude). Plus it would eliminate the hassles of pumped Lithium which are considerable.
Engineering is the art of making what you want from what you can get at a profit.
Re: Polywell vs Tokamak- using Deuterium and Tritium fuel
I have added a new thread for a D-D reactor boosted by B10 fission.KitemanSA wrote:Look at Figure 65 of this report. Says ~ 30x smaller.D Tibbets wrote:Or- comparing apples and apples...
If the Polywell can fuse deuterium- tritium (but not any other fuel) at high enough efficiency to make a power producing reactor- like a Tokamak, how would it compare to a Tokemak in size and cost. The x-ray problems, and drive conditions would be eased compared to D-D fusion or any other fuel. Size could presumably be smaller.
http://www.askmar.com/Fusion_files/EMC2 ... plants.pdf
Figure 66 also relates. Great report, though old.
viewtopic.php?t=1018
Engineering is the art of making what you want from what you can get at a profit.
Here is a thumbnail of how the D-T fusion reactor in a blanket would be configured.
Background
D + D -> T + p + 4.0 MeV
D + D -> He + n + 3.3 MeV
D + T -> He + n + 17.6 MeV
T + T -> He + 2n + 11.3 MeV
Breeding
n + 6Li -> T + He
n + 7Li -> T + He + n
The Polywell fusor in composed of hollow diamond coated carbon-carbon piping. The piping forms a heat pipe network cooled by silver vapor coolant whose cool side feeds a silicon carbide (SiC) radiator on the outside of the fusor unit. Any vacuum space inside the fusor is constructed by diamond coated SiC reinforced carbon-carbon composite. Such a fusor may produce a neutron fluence of 10^^20 neurons/second and operate continuously at 3000C.
The fusor is enclosed in a tungsten sphere 2 meters in diameter filled with argon gas. The argon gas transfers waste heat from the SiC heat exchanger to the surface of the tungsten sphere. The pure tungsten sphere is transparent to neutrons greater than 1MeV and passes them through to the blanket. The tungsten sphere is submerged in a 10 meter spherical blanket of filbe; a mixture of beryllium fluoride and lithium fluoride in this blanket and Thorium fluoride. The beryllium will moderate (reduce energy level) and multiply the 14 MeV neutrons by a factor increase of 1.8. The lithium will produce tritium.
Fission of Thorium/Uranium isotopes that is produced by neutron activation from the fusor will multiply the energy output of the fusor by a factor of 10. The operation temperature of this liquid blanket salt is 1200C and is circulated through a SiC primary heat exchanger to secondary heat exchanger which heats helium. Tritium is removed from the secondary heat exchange coolant. Helium drives a turboelectric generator at an efficiency of 60 %. The blanket is enclosed in a steel alloy enclosure. The blanket is maintained at subcritical levels by removing U233. Power output is regulated by the fusion pulse rate. Power output is 100 MWe.
Background
D + D -> T + p + 4.0 MeV
D + D -> He + n + 3.3 MeV
D + T -> He + n + 17.6 MeV
T + T -> He + 2n + 11.3 MeV
Breeding
n + 6Li -> T + He
n + 7Li -> T + He + n
The Polywell fusor in composed of hollow diamond coated carbon-carbon piping. The piping forms a heat pipe network cooled by silver vapor coolant whose cool side feeds a silicon carbide (SiC) radiator on the outside of the fusor unit. Any vacuum space inside the fusor is constructed by diamond coated SiC reinforced carbon-carbon composite. Such a fusor may produce a neutron fluence of 10^^20 neurons/second and operate continuously at 3000C.
The fusor is enclosed in a tungsten sphere 2 meters in diameter filled with argon gas. The argon gas transfers waste heat from the SiC heat exchanger to the surface of the tungsten sphere. The pure tungsten sphere is transparent to neutrons greater than 1MeV and passes them through to the blanket. The tungsten sphere is submerged in a 10 meter spherical blanket of filbe; a mixture of beryllium fluoride and lithium fluoride in this blanket and Thorium fluoride. The beryllium will moderate (reduce energy level) and multiply the 14 MeV neutrons by a factor increase of 1.8. The lithium will produce tritium.
Fission of Thorium/Uranium isotopes that is produced by neutron activation from the fusor will multiply the energy output of the fusor by a factor of 10. The operation temperature of this liquid blanket salt is 1200C and is circulated through a SiC primary heat exchanger to secondary heat exchanger which heats helium. Tritium is removed from the secondary heat exchange coolant. Helium drives a turboelectric generator at an efficiency of 60 %. The blanket is enclosed in a steel alloy enclosure. The blanket is maintained at subcritical levels by removing U233. Power output is regulated by the fusion pulse rate. Power output is 100 MWe.
Axil,
It is going to take a couple of weeks of engineering to get all that worked out and couple of months of manufacturing engineering to make it produceable.
Multiply by what ever scale you think is appropriate.
BTW tungsten filaments in tubes are run at about 2,700 deg C for life considerations. 2,300 deg C might be better from a life of the reactor standpoint.
SiC is not a very good heat conductor and it is brittle. And very hard. It is difficult to machine.
And fission of heavy metals is a nasty business. And if Xe137 is produced in any quantity you have a neutron sink that has to be addressed.
Interesting idea though.
But as I said up thread - if D-D is doable do it. No fuel breeding required.
It is going to take a couple of weeks of engineering to get all that worked out and couple of months of manufacturing engineering to make it produceable.
Multiply by what ever scale you think is appropriate.
BTW tungsten filaments in tubes are run at about 2,700 deg C for life considerations. 2,300 deg C might be better from a life of the reactor standpoint.
SiC is not a very good heat conductor and it is brittle. And very hard. It is difficult to machine.
And fission of heavy metals is a nasty business. And if Xe137 is produced in any quantity you have a neutron sink that has to be addressed.
Interesting idea though.
But as I said up thread - if D-D is doable do it. No fuel breeding required.
Engineering is the art of making what you want from what you can get at a profit.
MSimon wrote:
SiC is not a very good heat conductor and it is brittle. And very hard. It is difficult to machine.
Interesting idea though.
But as I said up thread - if D-D is doable do it. No fuel breeding required.
Hexoloy SiC tubes are used in shell and tube heat exchangers in the chemical process industry. Hexoloy's virtually universal corrosion resistance, high thermal conductivity and high strength allow for performance which cannot be equaled by other materials. Tubes are available in a variety of diameters and in lengths of up to 14 feet.
SiC is usually manufactured by vapor disposition.
The tungsten shell temperature will be well under 2300C because of blanket cooling. The fusor structure runs at sustained high temperatures only.
No problem: fission of liquid heavy metals done back in 60's and 70's at Idaho Nation Lab.And fission of heavy metals is a nasty business. And if Xe137 is produced in any quantity you have a neutron sink that has to be addressed.
French are prototyping it now.
Remove of gaseous fission waste was profected in the 1970’s at Idaho National Lab. Tritium removal is routine and can be accomplish in the same process.
Refererence:
https://lasers.llnl.gov/missions/energy ... ture/life/
A similay system is under development at Lawrence Livermore National Laboratory except with TRISO format fuel (depleted U238) and lasers.
Polywell can get a piece of $20 billion nuclear waste fund as a waste burner. There is a need.
What Mr. Tibbets has described is akin to an accerator driven Thorium Fueled molten salt reactor using the Polywell in lieu of the accelerator driven spallation neutron source.
The molten salt reactor was studied and several prototypes were build at Oak Ridge National Labs in the 50s and 60s. One incarnation was Thorium fueled.
It is, after a pBj (thanks MSimon) BFR, my farovite candidate for long term energy security. The BFR I hope will work, the MSR I know will work.
The molten salt reactor was studied and several prototypes were build at Oak Ridge National Labs in the 50s and 60s. One incarnation was Thorium fueled.
It is, after a pBj (thanks MSimon) BFR, my farovite candidate for long term energy security. The BFR I hope will work, the MSR I know will work.
IMO, the one advantage that a molten salt /Polywell fusor has over a standard Liquid salt fluoride reactor (Lftr) is that the excess neutrons from the fusion process mitigates the need to reprocess the core salt to sustain fission. That makes the sealed Lftr operationally simple and enables it to operate for 50 years without manipulation of the core salt(Nasty soup ).MSimon wrote:When I say fission is a nasty business I'm talking about the diverse array of radionuclides produced. Nasty soup that.
Great minds... ?Axil wrote: IMO, the one advantage that a molten salt /Polywell fusor has over a standard Liquid salt fluoride reactor (Lftr) is that the excess neutrons from the fusion process mitigates the need to reprocess the core salt to sustain fission. That makes the sealed Lftr operationally simple and enables it to operate for 50 years without manipulation of the core salt(Nasty soup ).
viewtopic.php?p=11023#11023