farmerben

Lithium Boron salts on spallation targets

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Posted (edited)

Protons >500 keV can cause disintegration of Li7 and B11. A Farnsworth Fusor device can achieve these voltages, but because the cross section for these disintegrations is low, it cannot recoup the energy used to accelerate the initial protons on Earth. 

Li7 + p = 2a +17.2 MeV
B11 + p = 3a + 8.7 MeV

Meanwhile the cross section for protons in metals like Bismuth is quite high. Although most of the protons will thermalize, a percentage of them will create neutron spallation events with over 20 neutrons. These self moderate and breed the element Polonium. At a certain thickness, many cold neutrons will escape the target. 

Lithium 6 and Boron 10 love cold neutrons

Li6 + n = a + H3 + 2.75 MeV
B10 + n = Li7 + a + 2.79 MeV

Such a device can become extremely profitable under two conditions. 1) There is a way to capture >500 keV protons without investing much energy into them. 2) Some of the tritium and its sister He3 can be sold for billions of dollars. 

The first condition can be satisfied at an altitude of 20 km above the Earth. 

The second condition could be achieved by capturing some of the H3 in a blanket of nitrogen dioxide, running it through heat exchangers, a tiny O2 bubbler, and to a cryo freezer. This would create tritium water ice and dinitrogen tetroxide. The tritium water is promptly frozen under pressure and agitation to contain as many gas bubbles as possible, these might be almost entirely He4 bubbles initially, but they provide the space for He3 from tritium decay.

 

 

 

*edit* should say 20,000 km above Earth

Edited by farmerben

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Posted (edited)
2 hours ago, Nightside said:

What industries use these products?

ISRU for tritium and helium-3 powered by solar wind for free. A tritium windmill.

Just keep delivering boron and lithium to the orbit.

Edited by kerbiloid

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10 hours ago, kerbiloid said:

ISRU for tritium and helium-3 powered by solar wind for free. A tritium windmill.

Just keep delivering boron and lithium to the orbit.

Awesome name!  A tritium solar windmill.  

Another concept is to use the Sabatier process to create tritium methane.  Then a Na-Cl process converts methane to ethane.  Add water to ethane and it becomes ethanol. 

Tritium whiskey!

 

 

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2 hours ago, farmerben said:

Awesome name!  A tritium solar windmill.  

Another concept is to use the Sabatier process to create tritium methane.  Then a Na-Cl process converts methane to ethane.  Add water to ethane and it becomes ethanol. 

Tritium whiskey!

 

 

wouldn't the beta decay be bad for your liver?

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2 hours ago, Nuke said:

wouldn't the beta decay be bad for your liver?

I think the only people who pay billions of dollars for tritium are the British taxpayers.  It could mean more funding for the NHS.

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2 hours ago, Nuke said:

wouldn't the beta decay be bad for your liver?

I think the only people who pay billions of dollars for tritium are the British taxpayers.  It could mean more funding for the NHS.

 

btw:  This is an awesome source for many proton spallation interactions.  https://www.oecd-nea.org/janis/book/book-proton.pdf

 

And Wikipedia has good charts of Van Allen flux.  

 

Li7 + p (2.2 MeV) = 2a (17.2 MeV)  will probably occur at least once per cm^2 s for absolutely free in Van Allen radiation.  A cathode system or a magnetic nozzle would scoop up more protons.  The particle acceleration factor is irrelevant, a nozzle/scoop system would effectively just increase flux by drawing from the areas around it.  

 

Correct me if I'm wrong but alpha particles with 9 MeV are travelling about 9% of light speed.  

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Posted (edited)

On an aside: I just realized why I shouldn't build a space station at that altitude out of Bismuth...

 

Bismuth is very weakly radioactive. Polonium 210, however...

Edited by Pds314

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2 hours ago, Pds314 said:

On an aside: I just realized why I shouldn't build a space station at that altitude out of Bismuth...

 

Bismuth is very weakly radioactive. Polonium 210, however...

I was seeing that as a feature, not a bug.  

 

Polonium is by far the most concentrated energy storage system we have.  1 gram gives of 140W of alpha rays at 5.3 MeV.  And it decays into stable lead very quickly.  

I think it would be perfect for equipment to dig tunnels on the moon.  Even if there were accidents, after few years all traces of contamination would be gone.  

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Wow, funny timing. We were doing the Boron reaction last week at work! We built our parts with glue filled with Boron Nitride, a low mass high thermal conductivity powder that's very useful for electronics in parts that experience certain kinds of radiation. We, of course, wanted to see what protons would do to our parts and they came out of the proton beam "screaming" according to the tech in charge who pointed a geiger counter at them.

I think it would be very hard to get useful power from though. The 8.7MeV energy isn't _that_ high, and the vast majority of protons will probably get stuck in the Boron before they can react. Once the protons get down into the keV, their range before they stop in Boron or Boron Nitride will be very short- order 1s or perhaps 10s of um just as a guess. All the electrons around the Boron just serve to slow the ~500keV protons down! Despite the high cross section (the high reactivity), I don't think the protons will travel far enough to meaningfully react. On the other hand, higher energy protons (50 MeV) can go quite far (1s of cm), but don't have anywhere as close to the same cross section (reactivity), so I think there's no good way to do it for Boron solids.

Lithium though I've never worked with. I'm curious now!

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Maybe the Jupiter radiation belts would do this more useful?

Then the Jupiter could be a fuel factory.

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