Boron Issues
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jamesr.
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July 28, 2010 at 12:42 am #861
rashidasParticipant[Admin Note: This was split off from More News Please thread. Refers to the crew talking about the boron and tackling the to-do list to be ready to incorporate it.]
Does the boron have to be very pure – reagent grade? or will 20 mule team borax do?
July 28, 2010 at 2:42 am #7510zapkittyParticipantrashidas wrote: Does the boron have to be very pure – reagent grade? or will 20 mule team borax do?
Fun question “_)
What I do know is that the proposed fuel at the moment is decaborane, which is composed of boron and hydrogen and I would think it’s normally manufactured to closer tolerances than the borax detergent…
It would be nice to be able to scoop raw borates and hydrates into a DPF reactor and keep it going but I suspect there’d have to be built-in miniaturized chemical refining plant to make that happen with the current designs 🙂
Then again if it’s a fusion reactor and you have enough fuel to get it started then an additional module containing such refining gear might just be a regular accessory…
… edits… can’t type worth beans today…
July 28, 2010 at 10:36 am #7515Brian HParticipantPure boron is available on the international market at reasonable prices. In any case, fuel costs are about a $1/megawatt year, or SLT. Not a factor.
July 29, 2010 at 8:11 pm #7522vansigParticipantdecaborane vapourizes and dissociates easily; but it is toxic, and so are the reagents that make it.
i doubt borax dissociates as easily. but it is cheap, and easier to handle.
so the real question i guess, is: would the oxygen or the sodium in borax create problems in the plasmoid?
July 29, 2010 at 11:14 pm #7525TulseParticipantvansig wrote: would the oxygen or the sodium in borax create problems in the plasmoid?
I would presume that reactions with those elements would not be aneutronic.
July 30, 2010 at 12:45 am #7526jamesrParticipantTulse wrote:
would the oxygen or the sodium in borax create problems in the plasmoid?
I would presume that reactions with those elements would not be aneutronic.
Their cross-sections for fusion are pretty negligible, even if you could get it hot enough so no need to worry about producing neutrons. But given their high Z of 8 & 11 respectively, even a few percent of them in the plasma would pollute it to the extent that it would radiate too much to achieve a sufficient temperature for the boron to fuse.July 30, 2010 at 3:29 am #7527Brian HParticipantvansig wrote: decaborane vapourizes and dissociates easily; but it is toxic, and so are the reagents that make it.
…My understanding is that B10H14 is a solid below 100°C, and boils at 213°C. If you’re in atmosphere at either of those temps, you’ve got more than poisoning to worry about!
July 30, 2010 at 11:49 am #7533HenningParticipantI just read on Wikipedia:
The physical characteristics of decaborane(14) resemble those of the organic compounds, such as naphthalene and anthracene, in that it can be sublimed under vacuum at moderate temperatures. Sublimation is the common method of purification.
So as we are working in a vacuum, possibly heating isn’t required at all.
July 30, 2010 at 12:00 pm #7534jamesrParticipantHenning wrote: I just read on Wikipedia:
The physical characteristics of decaborane(14) resemble those of the organic compounds, such as naphthalene and anthracene, in that it can be sublimed under vacuum at moderate temperatures. Sublimation is the common method of purification.
So as we are working in a vacuum, possibly heating isn’t required at all.
I think at the 10-40torr or so pressure FoFu will be operating you’ll need to warm it slightly to sublimate it. You also want the rest of the chamber warmed, as it would condense on room temperature surfaces & leave residues everywhere.
July 30, 2010 at 12:01 pm #7535HenningParticipantThere’s even a patent for a decaborane vaporizer:
July 30, 2010 at 10:20 pm #7537AeronautParticipantjamesr wrote:
I just read on Wikipedia:
The physical characteristics of decaborane(14) resemble those of the organic compounds, such as naphthalene and anthracene, in that it can be sublimed under vacuum at moderate temperatures. Sublimation is the common method of purification.
So as we are working in a vacuum, possibly heating isn’t required at all.
I think at the 10-40torr or so pressure FoFu will be operating you’ll need to warm it slightly to sublimate it. You also want the rest of the chamber warmed, as it would condense on room temperature surfaces & leave residues everywhere.
For the first shot in a series, since the cooling system can set the chamber wall temp wherever it works best for the fill pressure.July 31, 2010 at 11:47 pm #7543Allan BrewerParticipantrashidas wrote: Does the boron have to be very pure – reagent grade? or will 20 mule team borax do?
Naturally boron occurs as 2 isotopes – about 20% is Boron10 and 80% Boron11. Only the Boron 11 will participate in the desired fusion reaction. I am unclear as to whether the Boron10 would slowdown the reaction or just reduce it by 20%? So it might be necessary to do isotope purification before use – fortunately this is already done for nuclear fission power stations who use the Boron10 in reactor walls to soak up neutrons, so maybe we can get their by-product Boron11 cheaply!
August 1, 2010 at 3:37 am #7544Brian HParticipantAllan Brewer wrote:
Does the boron have to be very pure – reagent grade? or will 20 mule team borax do?
Naturally boron occurs as 2 isotopes – about 20% is Boron10 and 80% Boron11. Only the Boron 11 will participate in the desired fusion reaction. I am unclear as to whether the Boron10 would slowdown the reaction or just reduce it by 20%? So it might be necessary to do isotope purification before use – fortunately this is already done for nuclear fission power stations who use the Boron10 in reactor walls to soak up neutrons, so maybe we can get their by-product Boron11 cheaply!
I believe the design of the shell is water surrounded by a layer of B10, for neutron absorption.August 1, 2010 at 2:58 pm #7545jamesrParticipantWhen B10 absorbs a thermal neutron it doesn’t stay as B11. It is formed in an excited unstable state which decays in ~10^-12s to He-4 (1.47MeV) & Li-7 (0.84MeV) and a gamma ray photon (0.48MeV)
August 1, 2010 at 5:10 pm #7546AeronautParticipantjamesr wrote: When B10 absorbs a thermal neutron it doesn’t stay as B11. It is formed in an excited unstable state which decays in ~10^-12s to He-4 (1.47MeV) & Li-7 (0.84MeV) and a gamma ray photon (0.48MeV)
How does this translate for us laymen, Jamesr? Does the lithium accumulate, and if so, where and how fast does it accumulate? Does it need special treatment as a hazardous or commercial product? Is the boron coating weakened or diminished in any way by 5 years of operation at ~1khz?
Also, is the B-11 cheaply available as waste from refining boron into B-10? :question:
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