

Laser fusion put on slow burn - ananyob
http://www.nature.com/news/laser-fusion-put-on-slow-burn-1.12016

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eggoa
Relevant graph:

[http://commons.wikimedia.org/wiki/File:U.S._historical_fusio...](http://commons.wikimedia.org/wiki/File:U.S._historical_fusion_budget_vs._1976_ERDA_plan.png)

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simba-hiiipower
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 the same..

[1]
[http://en.wikipedia.org/wiki/Expenditures_in_the_United_Stat...](http://en.wikipedia.org/wiki/Expenditures_in_the_United_States_federal_budget)

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jerf
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.

~~~
simba-hiiipower
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.

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jerf
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.

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breckenedge
I'm all for fusion research. Love the idea of clean, inexhaustible power.
However, the NIF has consistently over promised and under delivered, and they
have no idea _what_ their problems are [1]. They could use a little restraint
when making schedule predictions.

[1] <http://fire.pppl.gov/NIF_NIC_report_rev5_koonin_2012.pdf>

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cjensen
Yep. NIF is such an old project that it was used as the "digitizer" in the
original TRON movie. Still no progress.

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shardling
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.

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cjensen
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.

~~~
uvdiv
_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...](https://en.wikipedia.org/wiki/National_Ignition_Facility#Driver_laser)

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leeoniya
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?

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snarfy
It depends on the type of fuel used. The holy grail is a boron + hydrogen
reaction, which produces three helium nuclei.

Since the nuclei are positively charged and moving quickly, the net voltage is
around 2 million volts. When done correctly, fusion will create electricity
directly. At that point it's just a matter of stepping it down to a usable
voltage, but we have lots of ways to do that.

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politician
Misleading title, from the article NIF is a weapons research project.

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ck2
_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 energy to do it would then be cheap.

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ChuckMcM
_"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 long before that it stops working as a nuclear warhead.

So what you do is you take put one on the shelf in the lab and you sample it
periodically to see how its content has changed, and run your simulations to
see if plutonium or uranium with those makeups would still work within the
boundaries of the device, and you try to test it periodically under conditions
that simulate, as much as possible, an actual explosion.

They used to do this at the test site, basically explode one warhead from a
batch every 2 - 3 years to insure they still worked. But they stopped when we
banned such testing.

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InclinedPlane
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.

