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Laser fusion put on slow burn

nature.com

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Re: Laser fusion put on slow burn

#21

Post by InclinedPlane »

ChuckMcM wrote: post #14
ck2 wrote: post #3

to help weapons scientists to care for the ageing US nuclear stockpile Simulating explosions helps determine maintenance for nuclear warheads? I would bet they were more likely trying to make a "nuclear" weapon without radiation/fallout and failed. I wonder what the world would be like with really cheap power though - I'd like to think a better place to live but more likely there would be a lot more war since the ene…

"Simulating explosions helps determine maintenance for nuclear warheads?" Yes. Radioactive material is, by definition, slowly becoming non-radioactive by decaying into other atoms. You can think of those other atoms as 'contaminants' in your plutonium soup. What this means is if you create a nuclear warhead, and put it on the shelf, if you did nothing you would have a very sophisticated box holding some lead. But lon…

That's not the only problem. Plutonium has numerous allotropes, and the allotropes have different material properties such as hardness and density. Given that creating super-criticality in a fission weapon is highly dependent on density and that the implosion dynamics are dependent on the properties of the fissile material this has a significant impact on weapons design. Given that an allotrope of Plutonium can change into another over time this makes keeping an eye on Plutonium based nuclear warheads quite necessary.

Additionally, radioactive decay releases Helium gas (alpha particles) over time which will lodge in the crystalline structure and cause disruptions over time.

Either of these factors can result in a change in the reliability and yield of nuclear warheads kept in storage for a long period of time.

Re: Laser fusion put on slow burn

#22

Post by jerf »

simba-hiiipower wrote: post #8
eggoa wrote: post #2

Relevant graph: http://commons.wikimedia.org/wiki/File:U.S._historical_fusio...

wow, that’s pretty sad. the 'moderate' path would have required an average expenditure of ~$2.5 billion a year, and projected the completion of a reactor by 2005. a pretty small investment when you consider the size of the federal budget [1] and where most of the funding goes. even more sad, when considering the likelihood that many graphs relating to other potentially transformative technologies probably look much t…

Uh... I would not take that graph as some sort of gospel. The truth is that even now we do not have an effective known path to economically viable fusion power generation, and if nothing else our computer simulations are indescribably better than anything they had in the late 70s. Had we blown billions more in the 80s, we probably would simply have blown billions more in the 80s and still have no fusion today.

Re: Laser fusion put on slow burn

#23

Post by throwit1979 »

simba-hiiipower wrote: post #8
eggoa wrote: post #2

Relevant graph: http://commons.wikimedia.org/wiki/File:U.S._historical_fusio...

wow, that’s pretty sad. the 'moderate' path would have required an average expenditure of ~$2.5 billion a year, and projected the completion of a reactor by 2005. a pretty small investment when you consider the size of the federal budget [1] and where most of the funding goes. even more sad, when considering the likelihood that many graphs relating to other potentially transformative technologies probably look much t…

$2.5B is roughly on par with the combined 2012 salaries of all NFL teams( $90MM - $118MM per team, at the cap ).

Which is as it should be, since football is far more important to humanity than something as silly as cheap, safe, and clean energy.

Re: Laser fusion put on slow burn

#24

Post by simba-hiiipower »

jerf wrote: post #22
simba-hiiipower wrote: post #8

Earlier quoted context omitted.

wow, that’s pretty sad. the 'moderate' path would have required an average expenditure of ~$2.5 billion a year, and projected the completion of a reactor by 2005. a pretty small investment when you consider the size of the federal budget [1] and where most of the funding goes. even more sad, when considering the likelihood that many graphs relating to other potentially transformative technologies probably look much t…

Uh... I would not take that graph as some sort of gospel. The truth is that even now we do not have an effective known path to economically viable fusion power generation, and if nothing else our computer simulations are indescribably better than anything they had in the late 70s. Had we blown billions more in the 80s, we probably would simply have blown billions more in the 80s and still have no fusion today.

that may be true, but getting it (or any new technology for that matter) to the point where it’d be economically viable requires an investment at some point..

and ‘blowing’ those billions in the 80s may very-well not have paid-off with economically viable fusion power today, but i highly doubt it would have left us with nothing to show for it.

Re: Laser fusion put on slow burn

#25

Post by gryphonic »

leeoniya wrote: post #4

one thing i never understood about fusion is how you can capture all the released energy efficiently enough. isn't it released in many ways that cannot really be harnessed directly eg: gamma radiation, x-rays, emf. that makes me think that the input:output ratio would need to be not just marginally better, but sufficiently better. does anyone know what the current best input:captured number is?

Usually you are trying to catch neutrons in a lithium blanket, and using the fission products to extract energy. At least that is what they are doing at ITER. The electromagnetic energy goes back into the plasma and helps with keeping things hot. The energy extraction is one of the biggest challenges with sustained fusion.

Re: Laser fusion put on slow burn

#26

Post by jerf »

simba-hiiipower wrote: post #24
jerf wrote: post #22

Earlier quoted context omitted.

Uh... I would not take that graph as some sort of gospel. The truth is that even now we do not have an effective known path to economically viable fusion power generation, and if nothing else our computer simulations are indescribably better than anything they had in the late 70s. Had we blown billions more in the 80s, we probably would simply have blown billions more in the 80s and still have no fusion today.

that may be true, but getting it (or any new technology for that matter) to the point where it’d be economically viable requires an investment at some point.. and ‘blowing’ those billions in the 80s may very-well not have paid-off with economically viable fusion power today, but i highly doubt it would have left us with nothing to show for it.

We don't really have a hell of a lot to show for what we have spent. Non-zero, sure, but a lot of the lessons we learned could certainly have been learned for a lot more cheaply if we hadn't tried to leap to the end of the process with grandiose projects built more on hope than science.

Re: Laser fusion put on slow burn

#27

Post by uvdiv »

leeoniya wrote: post #4

one thing i never understood about fusion is how you can capture all the released energy efficiently enough. isn't it released in many ways that cannot really be harnessed directly eg: gamma radiation, x-rays, emf. that makes me think that the input:output ratio would need to be not just marginally better, but sufficiently better. does anyone know what the current best input:captured number is?

isn't it released in many ways that cannot really be harnessed directly eg: gamma radiation, x-rays, emf.

Yes, just like nuclear fission! All this radiation gets absorbed by surrounding matter, and its energy becomes heat. Powers a steam or gas turbine -- just another heat engine (tm).

With fusion reactors, the radiation absorber is a blanket of pipes filled with molten metal, several meters thick and several tens of meters in inner diameter. There's a critical second purpose to this: creating fusion fuel. The molten metal contains lithium, which on absorbing neutrons transmutes to tritium (hydrogen-3), which can be scrubbed out and recycled. Tritium is fusion fuel; fusion reactors must create it like this in self-sufficient quantities.

About the fraction of energy captured; it's very close to 100% (only neutrinos escape), with the subsequent conversion from heat to electricity being some 30-50% efficient.

http://www.iter-industry.ch/wp-content/uploads/2010/01/Pr__s... (particularly first few slides)

http://aries.ucsd.edu/raffray/publications/JNM/ICFRM_10_Raff...

Re: Laser fusion put on slow burn

#28

Post by uvdiv »

cjensen wrote: post #20
shardling wrote: post #16

Earlier quoted context omitted.

What a silly thing to say -- of course there has been progress, even if it's only a better understanding of what doesn't work.

Only the US bothers with lasers because everyone else understands that lasers don't work for fusion. Tokamaks are where it's at. The only real use of NIF is to better understand fusion so as to better understand how nuclear weapons work. I just want them to be honest about it.

Only the US bothers with lasers because everyone else understands that lasers don't work for fusion.

https://en.wikipedia.org/wiki/Laser_Mégajoule

I personally think lasers are much more promising, if only because of how much room there is for disruption with solid-state lasers. Look at how horrible the NIF lasers are: ~1% efficient [0], billions of dollars, the size of a warehouse [1]. And the fusion end seems to work fine.

[0] https://lasers.llnl.gov/about/nif/about.php

[1] https://en.wikipedia.org/wiki/National_Ignition_Facility#Dri...

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