
New design could finally help to bring fusion power closer to reality - curtis
http://phys.org/news/2015-08-fusion-power-closer-reality.html
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DennisP
Meanwhile, MIT's fusion program is likely to be shut down soon. Their Alcator
C-Mod has the strongest magnetic field of any tokamak in the world, and made a
serious breakthrough in tokamak physics several years ago.

I had a chance to visit a couple years ago. A grad student showed us a metal
tie, about a meter long, and said they'd calculated that two of them could
hold down the Space Shuttle during launch. To hold the reactor together when
they switched it on, they needed 38 of them.

They hadn't run the reactor for a year due to funding issues.

~~~
mikeash
I had to run the numbers on that Space Shuttle thing, just to see. The Space
Shuttle weighed about 4.5 million pounds at launch, and had a thrust-to-weight
ratio of 1.5, meaning there was about 2.25 million pounds of net upward force
on it. So each of those metal ties was capable of carrying a bit over a
million pounds of load. Neat.

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dosshell
And in Si units about: 500 000 kg (453 592.37)

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gizmo686
kg is a unit of mass.The Si unit of force is the Newton.

~~~
richmarr
What's the SI unit of pedantry?

~~~
blackbeard
Easier to understand than the American/Imperial one :)

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iaw
The big problem with controlled fusion, as I understand it, isn't creating a
net energy positive fusion reactor like this article implies. The physics is
already there, we just need the engineering to catch-up.

The challenge is the materials that compose the reactor become brittle and
highly radioactive far faster than usable. Controlled fusion as an energy
source isn't just challenging because fusion is difficult, it's also
challenging because materials don't handle neutron bombardment well.

I think where this advancement is going to really help is in the iteration
phase due to lower build costs but I'm still waiting for a solution to the
radioactive economic issues associated with the materials these reactors would
be constructed from.

~~~
ZenoArrow
> "The challenge is the materials that compose the reactor become brittle and
> highly radioactive far faster than usable. Controlled fusion as an energy
> source isn't just challenging because fusion is difficult, it's also
> challenging because materials don't handle neutron bombardment well."

Isn't that problem solved with aneutronic fusion?

[https://en.wikipedia.org/wiki/Aneutronic_fusion](https://en.wikipedia.org/wiki/Aneutronic_fusion)

Of course we should focus on getting fusion working (working in the sense of
providing more energy than we put in), regardless of whether we use the
aneutronic approach or not, but as the field develops I'm optimistic we'll
find ways to have robust fusion reactors.

~~~
iaw
I can honestly say I'd never heard of that before you posted your link. I
don't know enough to form a valid opinion here.

~~~
derwildemomo
"I don't know enough to form a valid opinion here.".

Beautiful. This is pretty much the last thing I ever expected to read on the
interweb.

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throwaway_yy2Di
Here's the paper (no paywall):

[http://arxiv.org/abs/1409.3540](http://arxiv.org/abs/1409.3540)

Interesting that the liquid blanket is the same as in the molten-salt thorium
reactors (lithium beryllium fluoride (FLiBe)).

~~~
ethbro
Iananp, but wouldn't that be for the same reasons? E.g. in both case you're
trying to absorb energetic neutrons?

(Upon research:
[https://en.wikipedia.org/wiki/FLiBe#Coolant](https://en.wikipedia.org/wiki/FLiBe#Coolant))
Apparently it has properties that make it _both_ a great coolant & a neutron
moderator. Neat!

~~~
throwaway_yy2Di
They actually have nearly opposite goals. The fusion blanket is supposed to
transmute lithium to tritium [0] (create more fusion fuel), so it has capture
as many neutrons as possible. The fission-reactor coolant is supposed to be
transparent -- to capture as few neutrons as possible. Both of them need
isotopic separation of lithium to be practical. But in opposite directions.
ARC's FLiBe needs to be Li-6 enriched, and MSR needs to be Li-6 depleted.

The MSRE fuel used 99.993% Li-7 (your link), and the ARC blanket is 90% Li-6
(arXiv paper).

[0]
[https://www.iter.org/mach/tritiumbreeding](https://www.iter.org/mach/tritiumbreeding)

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glandium
_ARC: A compact, high-field, fusion nuclear science facility and demonstration
power plant with demountable magnets_

Can it be miniaturized to power a suit?

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Someone
_" The design could produce a reactor that would provide electricity to about
100,000 people, they say."_

It would be a huge step forward if this can be built, but there still would be
a long way to go. To scale that to "electricity for everyone in the USA", you
would need to build about 3,000 of these (or build much bigger ones). And
that's for _current_ electricity use, not if everybody starts driving an
electric car.

For comparison, a 1000MW nuclear reactor produces electricity for 690,000
_households_ ([http://www.nei.org/Knowledge-Center/Nuclear-Statistics/US-
Nu...](http://www.nei.org/Knowledge-Center/Nuclear-Statistics/US-Nuclear-
Power-Plants)), and US nuclear electricity generation is about a honderd times
that (same page)

~~~
mikeash
A fusion reactor able to produce net electricity _at all_ would be a massive
breakthrough. I don't think the size matters much at all. Once anything is
working, progress on scaling it up is likely to come quickly. The hard part is
getting to the point where it works at all.

The first nuclear power plant attached to a grid was only 6MW. The first
"full-scale" plant, according to Wikipedia and the BBC, had four reactors
producing only 60MW each.

~~~
Someone
Honest question: how does this design scale up?

Does scaling up mean making a bigger setup with magnets of the same strength?
If so, I agree it is just a matter of making the effort, but this 150-ish MW
thing is "half the size of ITER", which means it already is enormous (ITER
will be gargantuan with its 1400 cubic meter vacuum vessel).

Even at 'to the fourth power', I fear this would get really huge before it
significantly improves on our largest fission reactors.

Alternatively, can one inject more fusion material while keeping the same
magnetic field strength to get more power out without building a larger
device, or would that require stronger magnetic fields? If so, are we sure we
can make those stronger fields? (Correction welcome, but I don't expect we
can; if we could, we likely could scale this design down)

I still think that, if this works as advertised, it will be both a huge result
and only one important step on a long road ahead to 'free' clean energy.

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alexggordon
I think one of the biggest issues fusion power needs to deal with is whether
or not it's worth the money. Renewable energy has gained serious momentum in
the past years, and while it takes up significantly more land-mass-mass
(things like solar panels and wind turbines), it requires less research and
development than fusion, and is advancing at a significant pace. Contrast this
with something like nuclear fusion, that has been under development for
decades, and still has yet to produce a long term viable product.

The one area I still think I see fusion reactors succeeding in, is that they
can theoretically use nuclear waste as a fuel[0][1]. However, outside of
Transatomic Power, I really don't see many fusion companies interested in
dealing with that issue. Given fusions history of failure, I think that fusion
energy really needs a hell of a selling point beyond a simple "we make energy"
to be able to succeed. I think that selling point doesn't get much better than
using nuclear waste as fuel.

[0] [http://www.transatomicpower.com/](http://www.transatomicpower.com/)

[1]
[https://www.youtube.com/watch?v=4UXXwWOImm8](https://www.youtube.com/watch?v=4UXXwWOImm8)

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guenthert
Assuming this is the breakthrough the MIT press department makes it out to be,
remaining engineering and material sciences questions can be solved and a
commercially viable fusion reactor can indeed be constructed in the not too
distant future, do we actually want one?

Sure, this is fantastic news in a tech-geek, star-trek sense, but here in this
reality, can we actually deploy such a thing?

With the global climate in a delicate balance and energy released by fusing
atomic cores or splitting them or even any process yielding energy not
directly or indirectly gained recently from the sun is bound to increase the
average temperature. A single reactor might not make a relevant or even
measurable difference, but if a significant share of society's hunger for
energy is to be satisfied this way, then it will, won't it (and if we're not
sure, can we risk it)? So if this accelerates global warming, potentially even
leading to a runaway greenhouse process (reducing earth albedo by shrinking
the polar caps, releasing methane from the former perma-frost grounds in the
Siberian tundra, etc.), then I hope they find us earth 2.0 and a way how to
get there in a hurry.

~~~
ectoplasm
The heat produced by humans is trivial compared to the heat produced by
sunlight hitting the earth. That's why sources of energy that don't trap
sunlight are desirable.

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moreati
IANAP, but this sounds at least superficially similar to the reactor that
Tokamak Energy are developing. Any nuclear physicists care to weigh in?

""" Tokamak Energy is particularly focused on Spherical Tokamaks, pioneered at
Culham, because these compact devices can achieve a much higher plasma
pressure for a given magnetic field than conventional tokamaks, i.e. they are
more efficient.

Theoretical calculations show that a Spherical Tokamak using high fields
produced by HTS magnets could be significantly smaller than other fusion
machines currently proposed. For example, a compact ST power plant would have
a volume up to 100 times smaller than ITER """ \--
[http://www.tokamakenergy.co.uk/about-
us/](http://www.tokamakenergy.co.uk/about-us/)

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DrNuke
The lab demonstration, if and when hopefully achieved, will be great but still
a long way from full scale demonstration, licensing and commercialisation.
Physics may eventually work well but engineering must hold up at 1:1 and make
sense from several points of view. We're not there yet, ITER in Cadarache,
France, being the nearest and biggest shot. Fingers crossed.

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papasmrf
Curious, IANAP, but suppose they get this to work? What would happen in the
case of a magnetic field failure? I assume the magnetic field is generated by
running electricity through the new material? What if the power fails?

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Gravityloss
They use new high temperature superconducting wires to get those higher
magnetic fields. If those superconductor wires become commonplace, they have
some other uses as well...

