Talk-Polywell.org

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http://www.greentechmedia.com/green-lig ... next-year/

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Confusing article.
I thought the guys at Tri Alpha were using FRC- fusion like the guys at Helion?
According to Art, the guys at Helion dont think that PB will be possible, right?
Also, PB is aneutronic fusion, is it not? So how would that be useful for breeding fission fuel?
What the lasers of Lawrence Livermore have to do with that is beyond my understanding too. NIF wont do anything practical, if you ask me.

What a confused article? That they might showcase or at least describe the tech? I thought they already had described it? Monkhorst et al are well know as the protagonists [ http://www.talk-polywell.org/bb/viewtop ... 9299#19299 ] and haven't come up with any working device in the decades they've been funded to do so.

Not news.

Helion can not make p+B fusion because they have thermal plasma.
Tri alpha have non thermal distribution of p and B and can make p+B fusion, if there theory is right and Tod Riders theories are wrong.

If we're just making things up, why don't we say "Helion can make p+B fusion if the theory that says they can't is wrong"?

The article is confusing probably because the writer does not know much about nuclear processes. I think what the guy meant to say was if Tri-Alpha can do HB fusion, then you would just have a straight fusion plant as there would be little neutron flux. If not, then presumably they would run either DD or DT fuel-cycle, which would generate lots of neutrons that can be used to fission U238 or other fissile material that does not need isotopic separation.

It seems to me that a fusion/fission hybrid process makes sense for any DT fusion process. You're making lots of neutrons. Why not use them for something? I would think that such a hybrid plant would produce 2-3 times the energy of the fusion-only plant. The capital costs of such a hybrid plant would be higher, but the energy output should make it more economical on a per Watt output basis.

Such a hybrid system is the power plant analogy to the two-stage thermonuclear weapons we have in our arsenal.

I agree. The holy grail of breakeven means that you must kick utilitarian Goblets out of the way. I beleve, however, that U238 isn't somuch fissionable, but that it can be changed to P239 which is. Why not give a neutron to Th232 instead and avoid the Plutonium and the Trans Uranics of similar ilk? It'd take 7 neutrons to make plutonium from Th232, only one from Depleted Uranium (U238).

Give the Fusion Neutron to Thorium instead.

I think U238 (natural Uranium) is fissile with neutrons of the right energy. The secondary in a thermonuclear bomb uses U238 as a blanket for this purpose. Its the fission of this U238 that contributes about half the yield of a thermonuclear explosion.

in any case, you are correct that it is best to go to Thorium in the long run. However, there is lots of natural and depleted Uranium available for use.

BTW, you do know that many of our nuclear power plants are running on MOX made from decommissioned Soviet nuclear weapons. Talk about weapons into plowshares.

There is no point to a fusion/fission hybrid process. The only advantages of Fusion over Fission power generation are that it avoids the problems (mostly) of radioactive waste disposal and nuclear weapons proliferation. Soon as you start radiating fertile isotopes with the neutron flux you've negated all the advantages of Fusion power. If you are going to fool around with thorium and uranium you might as well just run a regular nuclear reactor at that point and save the money and complexity.

U238 does fission with high energy neutrons, about 30% of the power generated in a fast reactor (unmoderated) comes from U238 fission. However it's neutron economy is low enough that you can't achieve criticality with U238. A lot of neutron absorptions by U238 don't fission and you get a lot of plutonium and transuranics generated.

If you are running a DT reaction you will want to use a lot of your neutron flux to breed tritium to fuel your fusion reactor.

It's not necessary to use U238 as the outer blanket on thermonuclear bombs, but you do need a dense material as that blanket/tamper to focus the radiation/ablation pressure from the fission bomb trigger to achieve fusion. Using a U238 tamper does increase the energy output a great deal from the fission energy and makes the design easier and the fusion more complete. Unfortunately it's very dirty, generating a great deal more radioactive fallout.

BTW MOX is just a way to denature weapons grade plutonium. It is neither cost competitive with mined uranium nor does it do anything to reduce high level waste. Even at that it, it is not excessively difficult to extract the plutonium from the fuel or the waste if you have nefarious intent.

Not if all you have is a whole lot of thorium and not a lot of fissible isotopes of uranium.

Not to mention the fact that you don't need your fusion process to be energy positive.

It would be much simpler and cheaper to just breed the thorium into U233 in the reactor you are burning the U233 in. No need to bother with a fusion reactor.

Yes you can breed fissile material in a fusion reactor, but it doesn't make any economic sense to do so. There are simpler cheaper ways of doing the same thing.

Remember the only potential advantages of Fusion power over fission power are that it reduces the nuclear waste generated and the weapons proliferation risks. As soon as you start breeding fissile material in a fusion reactor you've thrown out your only advantages.

Uh huh, and where do you get the neutrons from?



Depends on the fusion reactor, doesn't it?



Nonsense. There's the issue of fuel availability (FAR more boron and deuterium in the world than fissible uranium-235), which you keep glossing over.

The point of a fusion/fission hybrid is that you can enhance the neutron economy of the reactor. Wouldn't it be nice to return I129 back into the pot? A well designed fusion/fission hybrid can be very cleaning in terms of waste, and actually produce a lot of useful isotopes beside.

I also get a big kick out of those that blame the physics and technology for Nuclear weapons proliferation. It takes 1940's American technology, 1990's *North Korean* technology to produce Nuclear weapons. A modern Fission/Fusion hybrid plant could easily be designed to be so much a higher threshold, that it would be the absolute worst choice for a rogue nation to attempt to use for Nuclear weapons.... Using such a complex and useful power reactor could easily be made the hardest way, and the most visible way to attempt to make nuclear weapons. A good design will force a rogue nation to pursue simpler methods. Why do people keep blaming physics of *more* complex technologies for nuclear proliferation? New reactor designs only need to be a higher threshold than tried and true technologies that everyone knows already works.

From the fission of the U233 in the reactor core. There are sufficient excess neutrons to breed the fuel needed to run the reactor. It's a breeder reactor.

No, the fission reactor is going to be cheaper than the fusion reactor and is capable of breeding it's own fuel. There is no advantage of the fusion reactor over the fission reactor, it provides no additional advantages. If you are breeding fuel, then fuel availability is not a problem.




Fuel availability is not an issue with fission either. Relative amounts are irrelevant as long as there is plenty to do the job. Even with U235 there are hundreds of years worth of fuel available and as soon as you start breeding from Thorium or U238 there is more than enough fuel to last any rational timescale. Any powerplant built in the next 100 years will be obsolete and decommissioned before there is any fuel shortage. It's pointless to deploy fusion plants now based on that reasoning.

Fusion powers big advantages over fission is nuclear waste and proliferation reduction. Fission reactors currently do everything else better and cheaper than fusion does.Tokamaks will probably never be cost competitive with nuclear power. The best hope for fusion is something like the polywell that can run aneutronic fusion and bring the infrastructure costs down enough to make it competitive.

Again I ask what is the advantage of breeding fissile material in a fusion reactor when you can do the same thing in the very same fission reactor you are going to burn that fissile material in? Politically because of proliferation concerns breeding fissile material in a fusion reactor is going to go over like a turd in a punchbowl.

Fusion power will have a big advantage and cost reduction in respect to Fission power only if a direct conversion route will be realized (pB11 or similar reaction). If this will be realized with one of the technologies that are actually in development (Bussard, LPP, TriAlpha) AND we can really expect a reduction in cost of electricity of 2/3 orders of magnitude as they suggest, than we will witness a new industrial and economic revolution.

Just imagine a world where aluminium cost is 90% cheaper than today cost....