Mining the Moon---for Helium-3

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MisterE

Gym climber

Small Town with a Big Back Yard

Apr 24, 2016 - 09:03pm PT

Let me diagram this sh#t out for you in a different way than Ed:

Massive population relying on science for the fix

+ stop-gap measures that make people feel better about consuming the planet during the largest human population boom in history
+ your rare rich person that actually cares about the 7th generation and gets everyone all feel-good
-everyone else sucking the marrow for privitization and personal gain

= The problems cannot be solved off-planet.

Ed Hartouni

Trad climber

Livermore, CA

Apr 24, 2016 - 09:22pm PT

the total number of fusion reactions (the 'yield,' Y) is calculated as:

Y = ∬dVdt n₁n₂〈σv〉/(1+δ₁₂)

the integral is over the plasma volume and over time, n₁ and n₂ are the ion densities of species 1 and 2, (δ₁₂ is the Kronecker-delta to count the number of fusions correctly).〈σv〉is the reactivity which is the thermally averaged cross section, assuming that the thermal distribution is Maxwell-Boltzmann. The ion temperature T, is assumed to be constant over the infinitesimal volume element in the integral.

We usually use the E=kT as the "temperature," where k is the Boltzmann constant 8.6173324(78)×10⁻⁸ keV/K

so an ion "temperature" of 1 keV is equivalent to 11.6×10⁶ K, this is a "low" ion temperature.

We are getting roughly Y=10¹⁶ for kT= 3 keV in time scales of 100 ps and volumes of 1.13×10⁻⁷cm³

with a reactivity roughly 10⁻¹⁸cm³/s for DT fusion, the ion densities are something like 10¹⁷cm⁻³

this is about "break even," the amount of energy in equals the amount out, G=1 but we need G=50 for power generation.

For D ³He at the same ion temperature, 〈σv〉= 10⁻²¹cm³/s giving a yield of Y=10¹³ a thousand times less than for DT.

Brokedownclimber

Trad climber

Douglas, WY

Topic Author's Reply - Apr 24, 2016 - 09:36pm PT

Thanks Ed-

I've digested a lot of that, but will also need to go dig out a few moldy textbooks to make sure I understand everything. So...what is the result of going to higher ion temperatures? Does the yield increase, or is your system temperature limited?

Edit: Looking at the graphs again in your previous post answered the question.

Mike Bolte

Trad climber

Planet Earth

Apr 24, 2016 - 10:55pm PT

I was waiting for Ed to weigh in.

Brokedownclimber

Trad climber

Douglas, WY

Topic Author's Reply - Apr 25, 2016 - 08:36am PT

From Ed's comments, He-3 in not the fuel of choice, but D-T seems to have promise? That raises the question of "where do we get that much Tritium?" The other component, Deuterium isn't in that great abundance here on Earth, either, On the other hand Mars has a 6x natural abundance of Deuterium relative to the Earth. So, maybe Robert Zubrin, the Chinese, and the Russians are also barking up the wrong tree in seeking to exploit the natural abundance of He-3 in the Lunar Regolith?

Sierra Ledge Rat

Mountain climber

Old and Broken Down in Appalachia

Apr 25, 2016 - 12:15pm PT

Of course, the best reason to get more helium is for Trimix gas blends! No more getting narc'd out of your mind when at 30-40 fathoms!

Helium is getting too damn expensive. We need to start mining the moon.

Balloons - what a colossal waste of helium.

Brokedownclimber

Trad climber

Douglas, WY

Topic Author's Reply - Apr 25, 2016 - 02:16pm PT

Spaceflight Update:

The ESA Sentinel-1B satellite was successfully launched using a Soyuz-2 launcher. First 2 efforts were scrubbed by weather, and the 3dr by technical problems in the launch vehicle. Today was a perfect launch, jus 30 minutes ago. I watched the launch webcast live from French Guiana.

Will post up a youtube as soon as available.

Brokedownclimber

Trad climber

Douglas, WY

Topic Author's Reply - Apr 25, 2016 - 05:16pm PT

Launch video of ESA Sentinel-1B

[Click to View YouTube Video]

Ed Hartouni

Trad climber

Livermore, CA

Apr 25, 2016 - 08:32pm PT

That raises the question of "where do we get that much Tritium?"

one way is by using a "breeding blanket" around the fusion reactor made of ⁶Li which reacts with the neutrons to produce tritium:

⁶Li + n → ⁴He + ³H

the cross section increases with decreasing neutron energy like E⁻² so the blanket would probably contain some neutron moderator (hydrogen) as well as the Lithium.

"Deuterium isn't in that great abundance here on Earth, either"
the natural abundance is 0.0312% by weight, the Earth's ocean weigh about 1.4×10¹⁸ tonnes, so the oceans contain about 4.4×10¹⁶ tonnes of Deuterium. This is probably sufficient for the needs of fusion reactions.

To set scale, the capsules we have are 1mm in radius, and contain mg quantities of tritium and deuterium, we have yields of 10¹⁶ which represents something like 17.6 MeV released per fusion, that adds up to 28 kJ per implosion... we want to get to 28 MJ per implosion using the same amount of DT fuel... so fuel is not an issue in energy production.

bottom line, no need to look beyond the Earth for fusion fuels.

Winemaker

Sport climber

Yakima, WA

Apr 25, 2016 - 09:45pm PT

Ed - Li6 is used in weapons to produce tritium during ignition, but the tritium is instantly burned in the reaction. In a power producing situation, with a lithium blanket, one would have to extract the tritium from the shell and then process it to use in a fuel pellet. With a half life of about 12 years, processing time would seem to be a limiting factor. Do you see some sort of constantly replaced lithium impregnated shell, with tritium extraction? With its short half life tritium is pretty intense so are there processing issues?

Ed Hartouni

Trad climber

Livermore, CA

Apr 25, 2016 - 10:33pm PT

liquid Lithium blankets would probably be the engineering choice which would then be processed in a time much less than the half life of Tritium...

healyje

Trad climber

Portland, Oregon

Apr 26, 2016 - 01:00am PT

Ed, from a previous post of mine upthread:

I personally don't have much faith that either inertial (NIF) or magnetic (Tokamak) confinement fusion technologies will ever produce utility scale power, but would be interested in hearing Ed's perspective on the matter. I was once a believer decades ago mainly due to a small private company in Ann Arbor called KMS Fusion that had a working compact inertial confinement rig (like truck size) - it sure seemed like it had great promise at the time.

So what's your take on the possibility of commercial-scale fusion power by any means? Am I wrong to despair of anything happening in my child's lifetime (not gonna happen in ours from the look of it all)...?

fear

Ice climber

hartford, ct

Apr 26, 2016 - 07:16am PT

I bet Ed gets "extra" TSA scrutiny when he travels to China.

Glad you're on the home team.

Brokedownclimber

Trad climber

Douglas, WY

Topic Author's Reply - Apr 26, 2016 - 07:42am PT

Playing the environmentalist "Devil's Advocate," here: so the way we get "clean fusion power," is keep on producing massive radionuclide wastes from breeder reactors in order to keep fueling thermonuclear reactors. After all, that's how we're going to get sufficient Tritium?

The other 'Red Herring" in the availability of Deuterium, is the numbers given were based on the total quantity of water in the Earth system. A huge amount of this water is in the form of the Polar icecaps, glaciers, and in environmentally protected areas. Hence-unavailable. The Tritium/Deuterium reaction also liberates Neutrons, which in turn, generate radioactive shielding and structural materials. This somewhat attenuates the desired freedom from environmental pollution.

The amount of both Tritium and Deuterium currently available is certainly sufficient for the experimentalists, but what happens when there will be that inevitable breakthrough in fusion research allowing power generation?
I'm looking at the future of human society. Availability of energy is what allows an increase in standard of living; energy is indispensable in agriculture. Sooner or later, we will wean ourselves from petroleum through use of alternative power sources. When that happens, the demand for both Deuterium and Tritium will increase astronomically. At that point, moving on to a more difficult set of isotopes to initiate will become necessary. We may not be able to get a He-3/Deuterium reaction to work now, but in the 22nd Century, all bets are off.

Ed Hartouni

Trad climber

Livermore, CA

Apr 26, 2016 - 08:53am PT

We may not be able to get a He-3/Deuterium reaction to work now, but in the 22nd Century, all bets are off.

then you should bet by investing in that technology. As a physicist, I'd caution that you will loose, but the loss would be to your legacy. Getting the reaction to "work" isn't a matter of fiddling around in the lab, it is a basic property of the reaction itself, the cross section for the reaction. The larger the cross section, the more reactions.

The fusion rector of the future has many unspecified engineering challenges, breeding tritium is just one of them. Certainly dealing with the neutron activation of the material surrounding the reaction is another, and the related problem of converting the neutron kinetic energy into a "useful" source of energy to produce electricity (or perhaps to extract hydrogen from water, etc.).

Most of these engineering issues await establishing an operating point for the fusion reaction that would be used in energy production, an operating point that is not yet established.

So what's your take on the possibility of commercial-scale fusion power by any means? Am I wrong to despair of anything happening in my child's lifetime (not gonna happen in ours from the look of it all)...?

Commercial scale fusion will require a major engineering program, which not only includes the power plants themselves but also the establishment of the "fuel cycle" and the economy to produce usable fuel. While many of these issues are the subject to various DOE programs, commercialization isn't necessarily predictable, it will depend, in this country, on a partnership between the government and industry, particularly on indemnification, economic risk reduction, etc. Not only that, but a fusion energy economy would be very disruptive, displacing the current carbon energy economy. The ramifications of that transition are not well studied (at least studies of that type are not known to me).

The various private efforts to produce viable fusion technologies are worthy approaches but are unlikely to produce economic energy sources.

But until we understand how to light a controllable, self-sustained burning plasma we can't really specify the steps to a fusion energy economy. While some very good research in inertial confinement fusion is possible at the NIF, and similar research commencing at ITER (hopefully soon) on magnetic confinement, I think it is currently impossible to predict when we'll understand that complex system well enough to embark on commercialization.

Predicting that future requires understanding things we don't even know about yet.

As for mining off of the planet Earth, one has only to look at the economics of oil to understand the balance of extraction costs to commodity pricing. The cost of energy would have to be extremely high in order to justify the costs of going to the Moon (or to Mars) to get the fuel.

There are completed wells that sit idle, essentially too expensive to run based on the price of the crude oil that could be extracted. Similarly, wind turbines sit idle on the hills above Livermore until the electricity they would produce can be sold at a price sufficient to overcome the operating costs of the running turbines.

The cost of energy that would justify extra-terrestrial fuel sources (the Sun excluded) would probably be economically impossible to achieve.

I'll try to fill that argument out with some estimates later.

Brokedownclimber

Trad climber

Douglas, WY

Topic Author's Reply - Apr 26, 2016 - 01:38pm PT

Ed-

Thanks for your input and opinion. One of the things which I want to direct to your knowledge and experience is the possibility of doing something those of us poor schmuck laboratory chemists have had to do all our careers: use one highly reactive component added to a mixture to "start a reaction" containing a similar but sluggish component. I'll use a specific example from my own experience, and that's the initiation of a Grignard reaction of Magnesium metal and 4-chlorostyrene. The reaction doesn't have the ability to "start" and get over the activation energy barrier. But we were able to get the reaction started by adding a very small amount of either Methyl Iodide, or even better, 1,2 dibromoethane. Once the dissolution of Magnesium metal began (exothermic), the desired reaction would then proceed in parallel with the trigger reaction and then sustain itself once started. The dibromoethane was ideal, since there were no undesirable side reactions and the side product (ethylene) is a easliy disposed of gas.
Isn't something analogous possible with your reaction system? Start with an appropriate mixture of your initiator--Tritium + Deuterium (in XS), along with Helium-3? From what you've been saying--or at least my reading of your elegant explanation--that initiation is the problem due to low ion temperatures.
You've pointed out that the neutron flux created by the T/D couple will need to be dealt with and that's an engineering problem, and some of the released energy may be utilized.
Believe me, I'm not trying to argue with you, but simply develop a correct scientific understanding of the problems facing this research!

healyje

Trad climber

Portland, Oregon

Apr 26, 2016 - 11:35pm PT

Ed, thanks for the rundown...

Ed Hartouni

Trad climber

Livermore, CA

Apr 27, 2016 - 12:28am PT

well it's a bit more complicated at NIF for ICF...

the capsule is plastic, there is a layer of solid DT on the inside of the capsule, and a DT vapor in the center.

the capsule ablates collapsing it, the temperature of the vapor goes like the ideal gas law: pV=NkT

at some point, the kT is large enough to start burning the vapor through fusion

when this happens, the alpha particles produced in the fusion will loose energy in the solid fuel and heat it, and it will start burning, this is called "ignition"

sustaining this burns the entire fuel load and we get the desired gain

the trick is to match the alpha particle range to the thickness of the DT solid layer

and to balance the conductive and radiative energy loss in the capsule