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Momentary fusion breakthroughs face hard reality

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Re: Momentary fusion breakthroughs face hard reality

#31

Post by thmsths »

_a_a_a_ wrote: post #30
wolverine876 wrote: post #27

Earlier quoted context omitted.

Why go through the expense of engineering and manufacturing a bomb, and then use it for a different purpose? If you want an electricity generator, engineer and manufacture for that. Or are you thinking of using excess bombs? I want to say that fusion bombs require more energy input than they output, because until recently nobody has been able to create fusion reactions otherwise (and now only in a very limited way).…

> Why go through the expense of... Good question. I should have asked strictly about fusion bombs. These being a known-working example of energy production by fusion, why not use them when we can't get 'controlled' fusion working?

From my recollection, even in a fusion bomb, most of the energy comes from the fission. I don't fully remember/understand the physics involved. But apparently the fission reaction triggers the fusion reaction (that part I get) and then that fusion reaction in turns boosts the fission reaction.

So my takeaway is that fission bombs are not very efficient to begin with. You're after all trying to extract as much energy as possible as quickly as possible from a system that is literally self destructing. We do not have that constraint with current fission plants, the plant is designed to run in a steady state for years, the fissile materials stay in place and my intuition is that this significantly helps efficiency.

Re: Momentary fusion breakthroughs face hard reality

#32

Post by throwaway44023 »

_a_a_a_ wrote: post #30
wolverine876 wrote: post #27

Earlier quoted context omitted.

Why go through the expense of engineering and manufacturing a bomb, and then use it for a different purpose? If you want an electricity generator, engineer and manufacture for that. Or are you thinking of using excess bombs? I want to say that fusion bombs require more energy input than they output, because until recently nobody has been able to create fusion reactions otherwise (and now only in a very limited way).…

> Why go through the expense of... Good question. I should have asked strictly about fusion bombs. These being a known-working example of energy production by fusion, why not use them when we can't get 'controlled' fusion working?

One of the biggest challenges is that the fusion reaction can't be fully contained. There are particles without electric charge that simply go through your magnetic containment field and smash into the reactor wall, continuously destroying it. You don't really care about preserving the shell of your bomb. You care about preserving the shell of your reactor.

Re: Momentary fusion breakthroughs face hard reality

#33

Post by philipkglass »

_a_a_a_ wrote: post #30
wolverine876 wrote: post #27

Earlier quoted context omitted.

Why go through the expense of engineering and manufacturing a bomb, and then use it for a different purpose? If you want an electricity generator, engineer and manufacture for that. Or are you thinking of using excess bombs? I want to say that fusion bombs require more energy input than they output, because until recently nobody has been able to create fusion reactions otherwise (and now only in a very limited way).…

> Why go through the expense of... Good question. I should have asked strictly about fusion bombs. These being a known-working example of energy production by fusion, why not use them when we can't get 'controlled' fusion working?

Let me elaborate on thmsths's answer. The United States developed and tested large "clean" fusion bombs that produced only a very small fraction of their energy from fission. Those bombs could produce raw thermal energy at a cost below any fossil fuel or conventional nuclear reactor. For example, the Housatonic test shot of Operation Dominic in 1962 yielded about 10 megatons and 99.9% of the energy released came from fusion [1].

The problem is that explosions of that magnitude are not usable for controlled energy generation. Confining them underground is impractical, due to the scale of energy release. The largest underground US test was 5 megatons in 1971, and it was so disruptive (induced surface motion equivalent to an earthquake) that it had to be conducted at a remote Alaskan island instead of the usual Nevada test site [2].

For those reasons, Project PACER considered bombs of only up to 50 kilotons. At those sizes (0.5% the energy yield of Housatonic), there is no known design to get 90%+ of the bomb's energy yield from fusion. The efficient fusion designs don't gracefully scale down to that range. And at that much smaller scale where underground confinement was practical, bombs were not actually any cheaper as a source of raw thermal energy. Quoting Wikipedia about the project here, "In a 1975 review of the various Plowshares efforts, the Gulf University Research Consortium (GURC) considered the economics of the PACER concept. They demonstrated that the cost of the nuclear explosives would be the equivalent of fuelling a conventional light-water reactor with uranium fuel at a price of $328 per pound. Prices for yellowcake at that point were $27 a pound."

[1] "Ripple: An Investigation of the World’s Most Advanced High-Yield Thermonuclear Weapon Design" http://web.mit.edu/zoz/Public/jcws_a_01011.pdf

[2] https://en.wikipedia.org/wiki/Cannikin

Re: Momentary fusion breakthroughs face hard reality

#34

Post by notfish »

megaman821 wrote: post #20
gene-h wrote: post #10

Earlier quoted context omitted.

NIF uses inefficient lasers because they were cheap to build at the time and because NIF is a science experiment. Lasers have gotten better. And lasers aren't the only way ICF fusion could be carried out, it may be possible to use ion beams instead[0]. It does not matter if fusion reactions last microseconds if they generate more energy. Using optimistic, but not unrealistic assumptions, it appears feasible for elect…

Those numbers don't seem feasible. Near as I can tell, a steam generator with a magical source of never-ending heat would cost $15/MWh. There is no way a high-tech facility and the personnel required to run it are costing $10/MWh.

What’s your math on $15/MWh? As far as I can tell, the steam turbine is a pretty insignificant part of the price of coal energy generation

Re: Momentary fusion breakthroughs face hard reality

#35

Post by AlbertCory »

JoeAltmaier wrote: post #15
tonetegeatinst wrote: post #14

Earlier quoted context omitted.

I think a lot of people who are really into fusion research know that the military isn't going to be doing the same kind of fusion research as the groups looking into fusion as an energy source. Is what they did interesting sure, but alot of people who actually follow fusion development know that this was a PR meme that some news stretched. Fusion has always been 20 years away its a literal meme....and yet we are mak…

The US military is very much interested in fusion, as an energy source. The Desert Storm conflict cost something like $1T (yes a Trillion dollars) just for gasoline. There was on this site a description of a military effort to create a low-yield fusion generator that would fit on a military truck. It only had to fuel a mobile camp, not a city. If I recall, it was something like the Lockheed plan, to create a vortex (…

> a low-yield fusion generator that would fit on a military truck.

another word for that is "drone target."

Re: Momentary fusion breakthroughs face hard reality

#36

Post by hbossy »

wolverine876 wrote: post #25
JoeAltmaier wrote: post #15

Earlier quoted context omitted.

The US military is very much interested in fusion, as an energy source. The Desert Storm conflict cost something like $1T (yes a Trillion dollars) just for gasoline. There was on this site a description of a military effort to create a low-yield fusion generator that would fit on a military truck. It only had to fuel a mobile camp, not a city. If I recall, it was something like the Lockheed plan, to create a vortex (…

I've read that the US military has looked into small fission generators. They expect logistics to be very difficult near the front if there is a war with a 'near-peer' (China or maybe Russia) and hope to reduce fuel logistics. I've never heard of them looking into similar fusion reactors. Why would they? Nobody expects to build any kind of production fusion reactor for decades, much less one that could be operated by…

American military would love to squeeze nuclear reactor on every single ship. The conventional escort ships are much slower than aircraft carriers and need constant refueling, to the point they sometimes leave them behind and sail meet another fleet in destination port. It's not really feasible with fission but fusion would make it a lot safer.

Re: Momentary fusion breakthroughs face hard reality

#39

Post by wolfram74 »

notfish wrote: post #34
megaman821 wrote: post #20

Earlier quoted context omitted.

Those numbers don't seem feasible. Near as I can tell, a steam generator with a magical source of never-ending heat would cost $15/MWh. There is no way a high-tech facility and the personnel required to run it are costing $10/MWh.

What’s your math on $15/MWh? As far as I can tell, the steam turbine is a pretty insignificant part of the price of coal energy generation

$15/MWh is 1.5 ¢/KWh, right? that's pretty darn cheap and means that the other 10~20 cents would be transmission and fuel, yes?
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