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MIT-designed project achieves major advance toward fusion energy

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Re: MIT-designed project achieves major advance toward fusion energy

#81

Post by orbital-decay »

zetalyrae wrote: post #49
dfdx wrote: post #34

Plenty of skepticism in these comments. I've been following CFS for a while and can present a point of view for why this time might be different. Fusion energy was actually making rapid progress in the latter half of the twentieth century, going from almost no power output in the fifties and sixties to a power output equal to 67% of input power with the JET reactor in 1997. By the eighties there was plenty of experim…

I've always wondered: why exactly is ITER so expensive, and slow? Is the engineering required at such a standard that it should takes decades of planning and construction and tens of billions of dollars? The timeline is so dilated (started in 1988, first plasma planned for 2025!) it feels like the kind of project that's expected to be cancelled from the start. It just doesn't strike me as obvious that reducing the ma…

Expensive because it's a custom built physics lab, not a commercial power plant. Slow because it's an international project. Not just that, but it also requires lots of infrastructure to be built and entire industries to develop in multiple countries, before it can be useful. ITER is massive, but it's also just a tip of the iceberg.

>It just doesn't strike me as obvious that reducing the major radius by a few meters would have such a huge impact on cost/timelines.

It would, easily. Past a certain size, production costs rise exponentially and require one-off tech.

Re: MIT-designed project achieves major advance toward fusion energy

#82

Post by maccam94 »

pcj-github wrote: post #76

If we had "an inexhaustible, carbon-free source of energy that you can deploy anywhere and at any time" we'd wreck the planet faster than we already are... I guess at least a few could escape though.

I'm curious whether we could cool the planet by pulling CO2 out of the air with scrubbers powered by fusion reactors, or if their heat output would cancel it out. Removing the CO2 would have the benefit of being an exponential thermal decrease (the planet gets less hot from the sun each day), and heat output from fusion plants should scale linearly with the rate at which the CO2 scrubbers run, so it's possible the scaling properties would work out...

Re: MIT-designed project achieves major advance toward fusion energy

#83

Post by UnFleshedOne »

Krasnol wrote: post #26
ChrisMarshallNY wrote: post #6

Earlier quoted context omitted.

The running joke has always been that “Fusion is 20 years away,” and has been, for the last 50 years. I really want this to work. I am a bit concerned, with how “the old guard” will react, once we have successful, productive, fusion. I foresee an astroturf NIMBY campaign against construction of fusion plants.

You don't need an astroturf. Nuclear ruined it's own reputation for generations though hopeful not as long as they'll have to care for the waste we already have.

What ruined nuclear reputation is environmentalists who don't actually care for environment.

Re: MIT-designed project achieves major advance toward fusion energy

#84

Post by onlyrealcuzzo »

orbital-decay wrote: post #81
zetalyrae wrote: post #49

Earlier quoted context omitted.

I've always wondered: why exactly is ITER so expensive, and slow? Is the engineering required at such a standard that it should takes decades of planning and construction and tens of billions of dollars? The timeline is so dilated (started in 1988, first plasma planned for 2025!) it feels like the kind of project that's expected to be cancelled from the start. It just doesn't strike me as obvious that reducing the ma…

Expensive because it's a custom built physics lab, not a commercial power plant. Slow because it's an international project. Not just that, but it also requires lots of infrastructure to be built and entire industries to develop in multiple countries, before it can be useful. ITER is massive, but it's also just a tip of the iceberg. >It just doesn't strike me as obvious that reducing the major radius by a few meters…

Is it massive because it's 6 meters? Like - a 6 meter diamond would be "massive" - but a 6 meter boat isn't that impressive.

Or is it massive like the tokamak is a 6 meter engine to a 100 km collider? Like there's a ton of other stuff being built in a massive structure?

Re: MIT-designed project achieves major advance toward fusion energy

#85

Post by fabiospampinato »

sbierwagen wrote: post #57
zetalyrae wrote: post #49

Earlier quoted context omitted.

I've always wondered: why exactly is ITER so expensive, and slow? Is the engineering required at such a standard that it should takes decades of planning and construction and tens of billions of dollars? The timeline is so dilated (started in 1988, first plasma planned for 2025!) it feels like the kind of project that's expected to be cancelled from the start. It just doesn't strike me as obvious that reducing the ma…

Here's a render of the completed reactor: https://www.iter.org/doc/all/content/com/gallery/media/7%20-... Note human for size. It's all completely bespoke scientific equipment hand made for this project only. The cryostat will be the largest stainless steel vacuum vessel ever made-- all welded by hand. After welding, a substantial number of in-vessel components have to be installed by threading them through access po…

Here's a similar picture for SPARC from wikipedia: https://upload.wikimedia.org/wikipedia/commons/thumb/7/74/SP...

Re: MIT-designed project achieves major advance toward fusion energy

#86

Post by pfdietz »

apendleton wrote: post #37
pfdietz wrote: post #28

Earlier quoted context omitted.

The ARC reactor design has 10x the volumetric power density of ITER. Unfortunately, the ARC design also had 40x worse power density than a PWR primary reactor vessel.

Is that the right metric? You wouldn't need to build a huge containment structure around it like you would for a PWR, so I'd imagine the power density of the plant as a whole wouldn't be anywhere near 40x worse. Why focus just on the primary reactor vessel?

Because the rest of the power plant will be similar (or also worse for fusion; consider the tritium handling facility or the robotic equipment for maintaining the fusion reactor). You would need a confinement structure, just to keep the tritium in (which will leak all over even in normal operation). So if you swap out a cheap PWR reactor for a much larger, and hence much more expensive, fusion reactor, you get a power plant that costs more than a fission power plant.

Viewed another way: if you could make a fission reactor with a power density as low as ARC, it would have so much thermal inertia that meltdowns would be essentially impossible. You should then ask why such fission reactors are not built.

Re: MIT-designed project achieves major advance toward fusion energy

#87

Post by cletus »

I've long been skeptical of ITER making any sense given its insane cost. I mean even it succeeds, then what?

Here's the truth: there's no such thing as free energy. Even if the fuel is so abundant it's actually or effectively free (eg deuterium), the energy isn't. Say it takes $50B to build a plant that produces 1GW of power, which I'll estimate at about 7TWh/year based on [1]. Let's also say it has a lifespan of 40 years and an annual maintenance cost of $1B going to up to $2B in the last 10 years.

So that's 40 years for 280TWh at a cost of $100B, which equates to $0.35/kWh if my math is correct.

I realize ITER isn't a commercial power generation project. My point is that people need to stop getting hung up on the fuel being "free". The lifetime cost of the plant can still make it completely economically unviable.

Second, the big weakness of any fusion design is neutrons. The problem people tend to focus on is that neutrons destroy your (very expensive) containment vessel with (one of my favourite terms) "neutron embrittlement".

As an aside, hydrogen fusion also produces high speed helium nuclei, some of which tend to escape and this is a problem too because Helium nuclei are really small so can get in almost any material, which is a whole separate problem.

But here's another factor with neutrons: energy loss. High speed neutrons represent energy lost by the system.

To combat these problems we've looked for alternatives to hydrogen-hydrogen fusion, the holy grail of which is aneutronic fusion. The best candidate for that thus far seems to be Helium-3 fusion but He-3 is exceedingly rare on Earth.

I really think we get caught up on the fact that this is how stars work but stars have a bunch of properties that power plants don't, namely they're really big and they burn their fuel really slowly (as a factor of their size), which is why they can last billions or even trillions of years. Loose neutrons aren't really an issue in a star and sheer size means gravity keeps the whole system contained in a way that magnets just can't (because neutrons ignore magnetic fields).

So I hope they crack fusion but I remain skeptical. Personally I think the most likely future power source is space-based solar power generation.

[1]: https://en.wikipedia.org/wiki/List_of_largest_power_stations

Re: MIT-designed project achieves major advance toward fusion energy

#89

Post by nixass »

ChrisMarshallNY wrote: post #6
dfdz wrote: post #2

The thumbnail of the youtube video made me laugh Smaller. Smarter. Sooner. 2018 Currently 2021 where is my fusion energy? But this time must be different, after this advance we are only a few years away from fusion energy?

The running joke has always been that “Fusion is 20 years away,” and has been, for the last 50 years. I really want this to work. I am a bit concerned, with how “the old guard” will react, once we have successful, productive, fusion. I foresee an astroturf NIMBY campaign against construction of fusion plants.

"Fusion is always 50 years away" for a reason

https://www.reddit.com/r/Futurology/comments/5gi9yh/fusion_i...

Re: MIT-designed project achieves major advance toward fusion energy

#90

Post by rnhmjoj »

speed_spread wrote: post #58
rnhmjoj wrote: post #50

Earlier quoted context omitted.

> But are they surmountable AND cheaper than existing nuclear or other energy sources? DT fusion solves the two biggest arguments that are always raised by nuclear energy opponents: storage of nuclear waste (it doesn't produce high-level waste) and safety (it's not perfect but it can't explode). I wouldn't call it a "meh", even if it comes off as much more expensive than fission.

It sounds like the T production chain might itself be quite messy. Molten isotopes salt and lead? How much of that stuff would you need? What do you do with when it goes bad? It may not go boom Chernobyl-style, but it's still far from the birds-in-the-sky deuterium-from-the-sea fusion dream.

> It sounds like the T production chain might itself be quite messy.

It is: it's definitely the biggest challenge after plasma confinement.

> Molten isotopes salt and lead?

There are two main blanket technology in development: ceramic and liquid breeders. They're called breeders but are very different from the kind of breeders you have in a fission reactor. Both are based on converting lithium to tritium by capturing fusion neutrons, but in one case the lithium is in the form of solid pebbles, while in the other, in a molten mixture of lithium-lead (there are no salts AFAIK).

To produce more tritium than you start with you also need a neutron multiplier: beryllium in ceramic breeders and lead in liquid breeders. The problem is beryllium is rare (and also toxic): a 500MW reactor needs ~200 kg/year, which is not a lot, but there's very very little beryllium on earth. If you factor in the initial reactor inventory (170 t/reactor) it turns out ubiquitous fusion energy it's not sustainable if we choose beryllium. If you go with lithium-lead you need more material: 3 t/year (but remember lead is a lot heavier and more common too). If you plan to cover the world energy base load with fusion, you would need a lot of lead (~10% world annual production) but it's doable.

For me, the biggest problem right now is lithium: DT fusion needs lots of pure ⁶Li, which is extracted by enriching even more natural lithium. If we're not careful enough with recycling it from old batteries, we are likely to exhaust the world resources in a few decades.

> What do you do with when it goes bad? It may not go boom Chernobyl-style, but it's still far from the birds-in-the-sky deuterium-from-the-sea fusion dream.

The worst case scenario is still the loss of coolant accident (LoCA). The blanket is exposed to a ~2MW/m² heat load from the plasma (in addition to all kind of radiation), so failing to cool adequately a module means it will very rapidly turns into a (radioactive) molten mess that's not easy to handle. Yeah, it's bad but not nearly as bad as the same accident in a fission reactor.

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