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3 years ago by hangonhn

The MIT Club of Northern California posted a video a few years ago on this exact topic and reactor:

https://www.youtube.com/watch?v=KkpqA8yG9T4

This thing came out of MIT, at least according to the video, and was really the collective efforts of a bunch of MIT grad students who made the breakthrough partially by taking a very Silicon Valley startup approach of using off-the-shelf parts, experimenting with new ideas, and starting small. I don't know if Professor Whyte framed it that way to appeal to the crowd or not.

3 years ago by elihu

Here's a more recent (1 year old) talk that gives a bit of a progress update: https://www.youtube.com/watch?v=rY6U4wB-oYM

3 years ago by Kliment

Here is an even more recent (last month) update https://www.youtube.com/watch?v=h8uYNhevRtk

tl;dw: SPARC is on track to Q=9, and there will be a magnet demonstrator in June, this year

3 years ago by dylan604

How in January 2021 after a full year of pandemic lockdowns and video conferences, has someone hosting something like this not invested in a microphone?

3 years ago by aqme28

I haven't seen that one, but here's another talk on the same topic in the context of fusion energy broadly, by some people involved https://www.youtube.com/watch?v=L0KuAx1COEk

3 years ago by azernik

As far as I can tell that framing is probably for crowd appeal. The real breakthrough here is the availability of high-magnetic-field superconductors, which push the size requirements for break-even down a lot and so put construction costs in reach of private investment.

(This is why MIT is at the center of the work - they have a really good materials science program that's good at working with these finicky ReBCO tapes.)

3 years ago by kregasaurusrex

An important part of the article mentions bringing down the cost of high-temperature ReBCO tape conductors, where SPARC itself needed more than entire than what existing companies would expect to produce in an entire year. Existing technologies using superconductors like MRI machines, large transformers/motors, and synchronous condensers for power generation have each benefitted from bringing down these costs as the use cases mature.

ITER's estimated timeline having a working reactor by 2025 is ambitious, but is also supply constrained in that they're projecting the need for more Nb-Ti and Nb-Tn exceeding current yearly production amounts as well. For reaching the end goal of affordable hyperscale energy production, it's promising to see demand increase in order for new competitors to invest in related research projects.

3 years ago by henearkr

What is Tn (in Nb-Tn)?

3 years ago by skissane

I'm assuming it is a typo/thinko for Nb-Sn.

3 years ago by skoocda

From Wikipedia:

For higher magnetic fields, higher-performance, but more expensive and less easily fabricated superconductors, such as niobium-tin, are commonly employed.

3 years ago by ChuckMcM

I have some hope for this approach, but as the article points out making reliable magnets is really the key. When a fusion reactor quenches, the plasma will basically eat the reactor through "hole" in the field. I keep hoping an effort to manufacture ReBCo coils directly will be successful, it would both make them less expensive and likely more reliable. However I expect it would require something like a 5-axis 3D printer capability.

Lastly, fusion power is one of the possible 'good' future events (unlike climate change, or nuclear war) that give me hope for the future of the planet.

3 years ago by Florin_Andrei

Controlled fusion seems one of the few awesome future things that's unambiguously good.

3 years ago by technofiend

Particularly if there's some way to capture carbon that's otherwise impractical due to energy requirements.

3 years ago by adrianN

Fusion power will likely not be significantly cheaper than solar and wind for this purpose. Fusion plants are probably quite expensive and won't have an infinite lifetime. The big benefit is that you don't need batteries, but that doesn't matter if you want to use the power for carbon capture.

3 years ago by pfdietz

Why is is unambiguously good? There's great reason to doubt it could be anywhere close to economically competitive. That makes its value pretty ambiguous, in my view.

3 years ago by ChuckMcM

I think that an argument can be made that it will always be economically competitive. That reasoning includes the 'fuel cycle' is non-waste producing, the economics of other energy sources continues to rise thus creating a wider window for economic recovery, the liability associated with fusion will always be less than the liability associated with fission, and as the carbon externalizations of fossil fuel are priced into its production it will become in-economic as well.

Well designed fusion power should come in at or below hydro-electric power without the environmental impacts or risks associated with dams.

3 years ago by why_Mr_Anderson

You are right, in short term, fusion has not much value. But in (very) long term, unlike fission, which no matter how incredible it is, is still only 'planetary-level tech', fusion is the first 'stellar-level tech' we've unlocked so far. If we ever plan to go somewhere else than Solar system, fusion is the key.

3 years ago by dmos62

Molten salt reactors and thorium fission is pretty exciting too.

3 years ago by pfdietz

Making reliable magnets is A key, but it's by no means the only one. Fusion faces many grave obstacles even if the magnets were totally reliable and cost nothing.

3 years ago by thewarrior

What are some of the others ? Iā€™ve heard even if everything worked the generated neutrons would eventually destroy the reactor.

3 years ago by pfdietz

That's one. Another showstopper is that all the energy has to be radiated through the wall of the reactor. By limits on this areal power density and the square cube law, the volumetric power density of fusion reactors will suck. Compare ITER (0.05 MW/m^3) or ARC (0.5 MW/m^3) vs. a commercial PWR fission reactor primary reactor vessel (20 MW/m^3). Stronger magnets don't save a reactor from this.

The large size and complexity of a fusion reactor also means their reliability is a huge problem. There are many parts and joins there, and the machine will be so radioactive hands on access will be impossible. A single leak of coolant into the vacuum chamber renders a fusion reactor inoperable (while a fission reactor can keep operating even with multiple fuel rod leaks.)

3 years ago by moogly

They're hoping to use a lithium "blanket" that would absorb and use the emitted neutrons to breed tritium (that's needed for D+T fusion anyway).

3 years ago by kaybe

I'm also thinking of the highly diffusive radioactive tritium gas which is a PITA to contain and work with.

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

3 years ago by dejv

For anyone interested in small fusion reactors there is another startup called Tokamak Energy with great Youtube channel: https://youtube.com/channel/UCuSlFJbBUIj1zfJLRnGXSow

3 years ago by pontifier

For anyone interested in even smaller reactors, I'm working on a device that believe might be able to scale down to the size of a button cell battery.

http://www.ddprofusion.com

3 years ago by jamiek88

Do you have any published papers on this? Iā€™m fascinated!

3 years ago by pintxo

They link a patent on their page: http://www.ddprofusion.com/US10354761.pdf

3 years ago by yholio

Some related discussion by fusor practitioners about the concept. It's a tantalizingly complex field where many have attempted and failed to find the pot of gold at the end of the rainbow: https://fusor.net/board/viewtopic.php?p=78286#p78286

3 years ago by pontifier

I haven't yet found anyone to help me to describe and analyze it with rigor.

3 years ago by Lucasoato

Is this somehow related to cold fusion?

3 years ago by pontifier

Not at all. I believe a Penning trap could have an oscillation mode which causes a single species to reach extremely high densities for short periods of time.

I'm hoping to try for a density record with my prototype. It may not happen, but I think I can get higher densities than NIF.

3 years ago by sien

There is a list of active fusion organizations at :

https://www.fusionenergybase.com/organizations

Also the fusion subreddit is reasonably active :

https://old.reddit.com/r/fusion/

For anyone after an up to date book on fusion The Future of Fusion Energy is good:

https://www.goodreads.com/book/show/43700662-the-future-of-f...

3 years ago by willis936

I can't say anything about that website since I am not familiar.

The subreddit is godawful and no one should waste their time.

The book is top notch and everyone interested should give it a read (assuming you care enough and have enough disposable income to afford it, it is not cheap).

3 years ago by sien

Where do you get fusion news?

There is news on that subreddit of all the fusion startups, even the lesser known ones like HB11.

The Kindle version of The Future of Fusion Energy is $US 12.

3 years ago by fuoqi

What about degradation of superconducting materials under high neutron flux which will be generated by a "commercial" load? IIRC modern superconducting materials rely on relatively fragile meta-structures, which can be easily damaged by a sufficiently strong radiation. Changing magnets one-two times per year does not sound good for economic viability of such reactors.

3 years ago by elihu

I think if I understand correctly, there'll be a fluid (FLiBe) between the plasma and the magnet coils that absorbs most of the neutrons. The FLiBe heats up and is used to boil water to power a steam turbine.

SPARC isn't particularly designed for durability, but for the ARC reactor which is meant to be the commercially-useful iteration they're looking at having solder joints on the superconducting magnet film so the whole top of the reactor can be removed so they can pull out the inner lining in one piece and replace it. (Apparently they figured out that regular non-conducting solder joints don't actually introduce very much resistance.) I don't think there's any plan to replace the ribbon.

3 years ago by jacquesm

regular non-superconducting solder joints. They conduct, just not nearly as good as the material itself at that temperature.

Still, interesting that that would not result in enough power to boil away the solder.

3 years ago by elihu

Yeah, that's what I meant. Thanks. I guess if the solder joints are super-thin, there isn't much resistance. But still, it defies intuition.

One of the other weird things the MIT group working on SPARC has been experimenting with that sounds like it totally wouldn't work but apparently it does is that they don't bother to insulate between the Rebco tape windings. The superconductor is just a thin layer on top of stainless steel, and the stainless steel is a sufficiently mediocre conductor that the vast bulk of the power takes the long way around following the superconductive layer rather than taking a shortcut through the stainless steel. Apparently the insulator is less durable than the tape itself, so not having to rely on it makes for a more durable device.

3 years ago by anonuser123456

>IIRC modern superconducting materials rely on relatively fragile meta-structures

The HTS 'tape' they use is very robust. A lot of the work they are doing is qualifying the coils and magnets under various scenarios.

3 years ago by willis936

Neutron flux at the coils is one of the primary things looked at in reactor studies. It is a factor in choosing the thickness of the lithium blanket and boron coating.

3 years ago by dogma1138

The lithium beryllium molten salt theyā€™ll use as a coolant and useful heat extractor should be enough to capture free neutrons.

Itā€™s the same mixture that is used in molten salt fission reactors so itā€™s neutron absorption profile of it is well understood.

As a bonus you should be able to extract tritium from the molten salt which means it will produce some of its fuel too so itā€™s a partial breeder reactor too.

3 years ago by undefined
[deleted]
3 years ago by andy_ppp

So their main advancement is stronger magnets with "rare-earth barium copper oxide (ReBCO) on metal tape" being wound into extremely tight loops (and is presumably extremely thin).

Will we enter into a tipping point of materials science that allows magnets strong enough and suddenly we get fusion and it becomes ever better as we make better superconducting magnets?

3 years ago by NortySpock

Fusion seems like it will advance the fastest through (a) materials science unlocking better magnets and (b) simulation and physical experimentation with reactor designs, including highly experimental designs.

Computational modeling seems to be helping as well:

https://ai.googleblog.com/2017/07/so-there-i-was-firing-mega...

Disclaimer: I am not a plasma physicist.

3 years ago by DennisP

That's pretty much what's happening here, fusion output increases with the fourth power of the magnetic field. Double the field, 16X the output. But if we take it much further, we'll reach a point where the limit is the structural strength of the reactor.

A few years ago I got to tour MIT's Alcator C-Mod, which had the most powerful field of any tokamak to date. A grad student showed us a metal tie rod, about a meter long, and said they'd calculated that two of them could hold down the Space Shuttle while it was trying to launch. To hold the reactor together while it was operating took 38 of those.

3 years ago by pfdietz

The peak on-coil magnetic field in the ARC design (from the 2014 paper) is 23 Tesla. The pressure of a 23 T magnetic field is 2100 bar, nearly twice the pressure at the bottom of the Marianas trench, and comparable to the chamber pressure of a handgun. 60% of the mass of their design was the stainless steel structure needed to support the magnets against the outward JxB forces.

Fusion's prospects would likely be helped some by plasma configurations with much higher beta than tokamaks. At least the experiments would be cheaper.

3 years ago by Valgrim

"Suddenly", no. They're targeting 2025 for the first tests if everything goes perfectly, 2027 for a first demo reactor, and we don't know how expensive a real reactor would be so we have no idea if this is the design that will one day unlock UNLIMITED POWER!

but on the scale of civilizations, yeah this could be it.

3 years ago by UncleOxidant

4 years in the fusion field is pretty "suddenly".

3 years ago by hackeraccount

Why is that fusion reminds me of the James Webb space telescope .... https://xkcd.com/2014/

3 years ago by fabian2k

I'm not sure how much potential improvement you can expect there in the near future. There's a pretty large jump between the conventional superconductors and the new high-temperature superconductors used here, I'd suspect that it'll take a long time of incremental improvement to build stronger magnets with these new materials.

There's a lot of practical problems with building very high-field superconducting magnets. I'm also not sure how much you can gain from the thinnness of the material, conventional superconducting magnets have a lot of non-superconducting material in there as well to conduct heat so that the magnet isn't immediately destroyed on a quench.

3 years ago by scythe

I remember being in high school and visiting the large magnet facility in Tallahassee at FSU (you know, where they levitate frogs). They explained to us that the superconducting coils were made of niobium-titanium alloy, and I remember asking: "aren't there better superconductors?". The answer was yes, there are, but they're insanely difficult to make or something, so we don't consider it practical, "maybe someday".

It looks like "someday" finally got here -- the cuprates are being used in practice.

3 years ago by zafka

Are there any startups working on the material science side of making these magnets? It seems like a very tight engineering team might do well here.

3 years ago by elihu

In one of the SPARC talk videos I think someone asked who makes the Rebco film, and the speaker said there were a handful of small companies around the world. I don't remember if he was any more specific than that, but anyways it seems it's kind of a novelty low-volume product at this point. I assume with demand picking up that manufacturing capacity is going to grow along with it.

Low temperature superconductors in general is, of course, an active area of research. There may be better alternatives to Rebco just waiting to be discovered.

3 years ago by clarkrinker

Fusion is one of those topics where I'm always going to click on the comments before I click through to the article. There's a lot more to learn from you than from the link. Thanks for being here HN.

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