Tests show high-temperature superconducting magnets are ready for fusion

https://news.mit.edu/2024/tests-show-high-temperature-superconducting-magnets-fusion-ready-0304

by paulsutter • 2 years ago

235 105 2 years ago

news.mit.edu

CrzyLngPwd• 2 years ago

...in thirty years.

People have been saying this for 5 years on every Commonwealth Fusion article as they hit every milestone exactly on time. It's happening this time, people rushing to make fusion jokes are getting downvoted because it's apparent you're just keyword-matching fusion then snarking.

pfdietz14• 2 years ago

The problem I have can be see by going back to the original ARC paper. That reactor was much smaller than ITER, and had 10x power density, but was still the mass of several WW2 destroyers (for net 190 MW(e)). Its volumetric power density is still 40x worse than an existing commercial PWR.

dotnet00• 2 years ago

I think they're getting downvoted because the joke is getting really worn out and endlessly dismissive cynicism is just annoying.

gerdesj• 2 years ago

I went to Abingdon School, which is quite close to Culham labs (JET) in Oxfordshire, in the mid 1980s. One of my A levels was Physics. We had some boffins from JET pop on over and do a presentation to us about what they were up to. I was one of the thickies. Some of my (then) compatriots are now dons and even proper scientists! I only managed a random walk into IT.

I dimly recall a graph showing progress on how they were able to fire up the thing and the energy out compared to energy in. That graph had quite a decay on it initially but a really long tail. That long tail is where the always 25 years off meme comes from.

Nuclear fusion as an energy source is a massively complicated beast. You might like to note, say, that building for Hinkley Point C (a fission plant, Somerset, UK - just up the road from here) was started late 2018 and was due to be commissioned in 2023 and now is due in 2030. You might also note that aircraft and the like tend to take 20+ years to go from concept to service. A nuclear fusion plant will take quite a while to commission once a concept has been thrashed out.

Perhaps CF have got it sorted but there is a damn good reason for the always 25 years off "joke" - I was told it over 30 years ago by physicists working and already long time served at the coal face.

cubefox6• 2 years ago

People have been saying this for 5 years on every Commonwealth Fusion article as they hit every milestone exactly on time.

Interesting, so what is their timeline for commercial fusion?

catchnear43212• 2 years ago

only needs hydrogen atoms for fuel rather than rare and dangerous elements like uranium and plutonium

hydrogen isn’t exactly the safest element. not that any element is truly safe if used in the wrong way.

porkbeer• 2 years ago

How is it unsafe? I just electroplated on my desk and hydrogen was formed (right next to pure o2) with zero danger. Sure, an accumulated mix near stoich might be an issue, but that is easy to avoid.

catchnear43212• 2 years ago

and you can split water and make neat bubbles of two elements. more likely to shock yourself than make a boom.

most elements are safe if you handle them properly. that assumes nothing outside of your control. and no one.

maximus-decimus• 2 years ago

https://www.youtube.com/watch?v=fURATK5Yt30&t=173s

u3202• 2 years ago

So he's pushing an energy solution that requires Tritium. One of the rarest elements of earth. And then has the nerve to accuse fission of relying on rare elements.

refulgentis4• 2 years ago

Who is he?

Where did he push tritium?

Is the word tritium in the article? (Chrome can't find it.)

Is hydrogen more common than uranium?

Is hydrogen more common than plutonium?

What quote demonstrates "accuse", as in, "they had the nerve to accuse"?

These are honest questions, I hope you don't take offense.

Full disclosure: I live in Cambridge, MA, where MIT is located.

willis9366• 2 years ago

Why is it rare? Because it decays.

Why would anyone make a plan to use it as a fuel without a plan to generate it? They don't. You breed it in the blanket that collects the energy. The energy balance is quite positive.

dang• 2 years ago

Url changed from https://futurism.com/the-byte/mit-magnets-ready-fusion, which points to this.

(Normally we prefer the best third-party article to a corporate press release but the balance of information here points the other way.)

Edit: I should say that if there's a more informative third-party article, we can switch to that.

bananapub• 2 years ago

I really wish people involved in fusion research, and their university/corporate PR colleagues, had not spent the last forty years poisoning the fucking well. fusion power is still so far away that it can't even figure in to our plans for reducing emissions to zero, and yet people still publish articles like this to muddy the waters and make it sound like it matters in the short term at all.

cubefox6• 2 years ago

The real question is whether it can ever compete against fission in terms of cost. Currently it looks like fusion power plants will be substantially more expensive than fission power plants.

Certhas5• 2 years ago

... which is considerably more expensive than solar + hydrogen.

rocqua• 2 years ago

How does that change if you account for waste disposal in the costs? From what I gather the nuclear waste of fusion has a much shorter half-life. That should make storage and disposal much easier.

u3202• 2 years ago

"Overnight, it basically changed the cost per watt of a fusion reactor by a factor of almost 40 in one day,"

So there is this myth that fusion enables unlimited cheap energy. This is 100% false. It's not unlimited at all. Most concepts relies on using lithium-6. That's not a super common element.

But more importantly, it's not cheap. That should be obvious, if you could reduce the cost per watt 40x and still not be competitive.

ianburrell• 2 years ago

Lithium is a super common element. They are mining tens of thousands of tons per year increasing rapidly as make electric car batteries. Lithium-6 is 5% of lithium. Fusion reactors only need tons for breeding blanket.

pfdietz14• 2 years ago

The original ARC design had 950 tonnes of FLiBe, which contains 115 tonnes of Li-6. This is a substantial fraction of the Li-6 produced for the entire US hydrogen bomb program, all for a single 190 MW(e) (net) reactor.

pinewurst• 2 years ago

It’s interesting that it took 3 years from the physical test until paper publication.

probablypower• 2 years ago

Publications often take a long time. Particularly novel topics that are difficult to review due to a lack of comparative material or willing expertise.

The fact that it took 3 years is a positive, as it means multiple parties rigorously reviewed and approved the material.

gpm• 2 years ago

Is there a good reason we aren't seeing REBCO magnets in all new MRI machines? Seems like not needing liquid helium would be a pretty big win for hospitals?

fabian2k• 2 years ago

They probably still can't carry the necessary current without helium cooling. There are some NMR spectrometers (which work essentially by the same principles as MRI machines) with high-temperature superconductors, but those are still cooled by helium. The lower the temperature is the more current you can pack into those.

Could also be that it doesn't make economic sense yet, they're still pretty new compared to classical superconductors.

refulgentis4• 2 years ago

Yes: Commonwealth Fusion essentially is buying the world's supply of it.

MRIs are a more mature market, i.e. > 1 units, and need to justify component switches not just for feasibility, but for profitability. Swapping out a known-good for something in such short supply isn't feasible, it's more expensive than liquid helium.

Source: https://spectrum.ieee.org/fusion-2662267312 "Over two years, the team managed to buy up most of the world’s supply of 4-millimeter-wide HTS tape"

actionfromafar• 2 years ago

Commonwealth Fusion is such a Fallout name

cyberax4• 2 years ago

Is there a good reason we aren't seeing REBCO magnets in all new MRI machines?

REBCO tapes are still very brittle, and MRI machines are notorious for the amount of banging they produce when active.

andbberger• 2 years ago

???

the gradient coils make the noise, and due to field homogeneity requirements, it is safe to assume the superconducting coil is not moved by the gradient coils

caymanjim• 2 years ago

MRIs don't consume much helium. Keeping them topped off is a trivial expense compared to the rest of the costs of the machine and operation. If there were a new design that didn't require helium, it would also have to cost less than current machines to make sense.

7speter• 2 years ago

Wait, isn't the byproduct of fusion helium anyway?

willis9366• 2 years ago

Yeah but you'd power a city for a year for 100 kg of helium.

ororroro• 2 years ago

There are already non-venting systems that use a reasonable amount of helium (7L) to manufacture and don't require refilling. It just was not a design consideration previously. https://www.philips.com.au/healthcare/resources/landing/the-...

JoBrad• 2 years ago

While 7 liters is less than 1,500, why would they call this a helium-free system?

pfdietz14• 2 years ago

I would say it's because the technology has not been matured enough.

I would also say the reason CFS has been getting funding is not because of fusion (although, hey, why not take that longshot bet), but because of the value of being able to make these magnets for non-fusion applications.

Certhas5• 2 years ago

If someone is knowledgable on this: What does this mean for ITER? Any chance to retrofit new magnetic technology into ITERs design?

johnbcoughlin• 2 years ago

It means nothing for ITER unfortunately. Changing the toroidal field strength implies a totally different plasma size, density, temperature, everything. ITER isn't designed for this strong of fields and the plasma they would confine.

elihu3• 2 years ago

I'm not super knowledgeable, but my understanding is that ITER was designed around the best superconductors known at the time, which meant making the whole thing really big.

A benefit of stronger magnets is that you can make it a lot smaller, and presumably cheaper -- which is what MIT has been working on with SPARC.

I don't know if it's practical to upgrade the magnets on ITER, but I'd expect it to be really expensive -- especially if they've already manufactured/installed the old magnets.

pfdietz14• 2 years ago

It would be completely impractical, since ITER is not designed to withstand the much larger JxB forces (which scale as B^2).

In the high Tc high field designs, the mass of the metal supports for the magnets dominates the reactor mass.

cyberax4• 2 years ago

Nope. And this is fine.

ITER is not a prototype of a commercial fusion reactor, it's a burning plasma laboratory. Its main goal is to study the plasma confinement technology.

magicalhippo• 2 years ago

ITER is also supposed to be the final step before a commercial reactor. If SPARC works well and they can keep the pace they're at to make ARC, then ITER might be a dead-end in that regard, no?

p1mrx• 2 years ago

Like virtually all electrical wires, conventional superconducting magnets are fully protected by insulating material to prevent short-circuits between the wires. But in the new magnet, the tape was left completely bare; the engineers relied on REBCO’s much greater conductivity to keep the current flowing through the material.

Much greater conductivity than what? I assume there are other non-REBCO layers in the tape, but the article neglects to mention them.

glatisaint• 2 years ago

Much greater than previous superconductors I would assume.

Tuna-Fish2• 2 years ago

Stainless steel. Which is a perfectly good insulator when the alternative is REBCO.

willis9366• 2 years ago

Presumably the hastelloy substrate.

https://www.nature.com/articles/s41598-021-81559-z/figures/6

baking2• 2 years ago

During a quench, almost all of the current is carried by the copper cap.

https://ieeexplore.ieee.org/document/10316632

Animats• 2 years ago

Than stainless steel!

If you have two resistors in parallel, the current in each is proportional to the ratio of the resistances. But what if one of the resistances is zero? Then all the current goes through that resistor. So if you have a superconductor in parallel with another resistor, all the current goes through the superconductor! Doesn't matter if the other resistance is very, very low, but still nonzero.

Reportedly some undergrad thought of this.

So the superconducting layer is bonded to stainless steel tape, which is strong, not brittle, and will go down to cyrogenic temperatures without problems. Most previous superconducting "wires" had brittle ceramic insulation, which was hard to wind into magnets.

This is really clever.

pfdietz14• 2 years ago

The other thing the normal conductor does is save the coil from exploding if the superconductor quenches and loses its superconductivity (1/2 L I^2 can be a lot of energy). Old low Tc superconductors used copper for this, I believe.

raziel2701• 2 years ago

I think there's another level to this, when you put a superconductor in contact with a metal there's a proximity effect that lowers the Tc of the superconductor. If you're using a superconductor that has a 4K Tc then you cannot afford to have your superconductor be weakened by the proximity effect. So the insulation is to prevent the proximity effect from happening.

Here, since you're using a much higher Tc material, if Tc is lowered by a few K you still have plenty of thermal budget, allowing you to take the hit from the proximity effect but be able to save on insulation.

chasil2• 2 years ago

Do any of these principles apply to liquid nitrogen applications?

The article outlines a plate design that incorporates steel/REBCO windings and cooling channels for liquid helium that seems to be modular and easily serviced.

REBCO is actually listed as a high-Tc material in the wiki below, but requires liquid helium.

If this were reworked into a liquid nitrogen design, could it reach 20 Tesla?

https://en.m.wikipedia.org/wiki/High-temperature_superconduc...

baking2• 2 years ago

There is a layer of steel on the bottom that provides the structure for the tape and a layer of silver on top of the REBCO ceramic layer for electrical connection, but the whole tape is coated in copper which is the secondary conductor. When superconducting, the tapes, which are wound in a coil, carry the current and the copper acts as an insulator between tapes, but if it stops superconducting, the copper can become a resistive conductor which helps prevent quenching.

elihu3• 2 years ago

It's kind of funny that that image looks an awful lot like the housing of a Mazda rotary engine.

I'd be curious if MIT / Commenwealth Fusion have made any progress on their "remountable magnets" approach.

The problem is that if you have to replace parts of the reactor, the magnets get in the way. I think they found that you could just solder the ends of REBCO film to each other and even though the solder isn't superconducting, the layer can be thin enough that it doesn't matter. So, they were looking at technology to take a tokomak apart by desoldering the REBCO, then they can replace whatever parts are inside, then solder it back together when they're done.

That seemed like a pretty hard problem, and not one they're trying to solve with SPARC (which is only meant to be a cheap prototype reactor, not something designed for a long service lifetime).

tw04• 2 years ago

It's kind of funny that that image looks an awful lot like the housing of a Mazda rotary engine.

You at least have to give the poor guy credit :). Wankel engines can be found all sorts of places including planes!

https://en.m.wikipedia.org/wiki/Wankel_engine

elihu3• 2 years ago

Sure, but I've only seen variations of the Mazda 13B disassembled up close. I don't know if other Wankel engine housings look quite the same.

mcnamaratw• 2 years ago

Why? MIT could just rein these people in, and the reputational damage would stop right away.

fallingfrog• 2 years ago

BSSCO is superconducting at much higher temperatures. Why are they not using that?

GlibMonkeyDeath• 2 years ago

"In practice, HTS are limited by the irreversibility field H, above which magnetic vortices melt or decouple. Even though BSCCO has a higher upper critical field than YBCO it has a much lower H (typically smaller by a factor of 100)[11] thus limiting its use for making high-field magnets."

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

nielsbot2• 2 years ago

I saw this presentation by Dennis Whyte years ago and it left me really optimistic about Sparc/Arc's chances...

He goes through a lot of the interesting design details, including why REBCO is such a huge difference and will make their commercial reactor design possible:

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

bmitc2• 2 years ago

The only thing is that there are tons of problems beyond just having strong magnets. Using REBCO tape for the magnets indeed solves the problems of reactor size by letting the reactor be much, much smaller than say ITER. But it does not solve the other problems of reactor design and operation.

nielsbot2• 2 years ago

I'm sure that's true.. but at least in this presentation they seem to have thought through most of them? I want to believe :)

pauljurczak• 2 years ago

20 K is high temperature? Well, I better take my mittens and ushanka off. I thought 77 K was the official threshold: https://en.wikipedia.org/wiki/High-temperature_superconducti....

willis9366• 2 years ago

You'd never operate a superconducting magnet at its crtical temperature.

Check out figure 5 here. The relevant bit is the vertical slice along the left edge. Crtical current density and internal magnetic field both go way up when you go below LN2 temps. You could make an LN2 HTS magnet, it just wouldn't be in the 1T+ class.

https://cds.cern.ch/record/2277484/files/Bruker%20HTS%20Fit....

Tests show high-temperature superconducting magnets are ready for fusion

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