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Nuclear fusion reactor in South Korea runs at 100 million degrees C for a record-breaking 48 seconds
(www.livescience.com)
this post was submitted on 06 Apr 2024
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when talking about fusion, just think the conditions of stars/the sun. In order to function correctly, it has to be ridiculously hot.
The race for fusion is how to maintain it, and eventually have a net positive transaction of energy out, to energy in ratio.
Hotter than the sun. The sun has an enormous gravity pushing things along. To compensate we use more heat.
I thought we used magnetrons and such, and the excessive heat was due to current inefficiency and control of the fusion process in containing the heat and it building up higher and higher.
The heat is needed so atoms collide enough to fuse without the high pressure inside a star. The trick is keeping the reaction going.
Stupid guy here, being ridiculously hot is the whole point right? Isn't a fusion reactor just an extremely complex steam engine?
The difficult bit is to keep the fuel fusing. At the temperatures and pressures that are needed to get atoms to fuse together the whole lot wants to blow itself apart. Being able to reliability sustain the reaction for any length of time is a big achievement.
Once we can get it to keep going, then yes, we can use the excess heat for power, although it'll probably involve turbines rather than an old school steam engine type setup.
It's moreso keeping it contained at those temperatures, so that it does not melt the container that it's in, and potentially explode.
There has to be some absolute next-level power backup to keep the containment field from failing.
Melting actually is not a seriously issue as while the plasma is very hot, it also has very little mass. Sparks are also ludicrously hot but with their little mass contain very little energy so pretty much anything but dry tinder is going to extinguish them before they can do any damage. You want to avoid loss of containment because you will have to clean the reactor vessel and maybe replace a couple of wall tiles but that kind of failure is far from catastrophic.
Though of course with current designs the reactor walls do get hot because that's how we intend to capture the energy: Pipe water through the walls to cool them, use the hot water to drive a couple of turbines. One of the holy grails to pine for after the current designs actually enter service is to look at ways to drive electrons in a wire directly from the plasma, no detour via heat. The other is aneutronic fusion.
That's actually really interesting, as I never heard of that before.
Yeah you're absolutely right, damn that'd be one hell of a Holy Grail touchdown moment for Humanity if we could pull that off, the direct transference, no "middle man".
From the link (for others like me and did not know what the word meant)...
I mean, in principle we can already do it: Fusion reactions tend to produce lots of electromagnetic radiation, and we can drive wires directly via electromagnetic radiation, the technology is called solar panels. Trouble being solar panels generally aren't good at absorbing X-rays.
Read the below from this article...
That's not the plasma that melts anything but neutron bombardment. The containment and fizzling out issue is the same whether the plasma produces neutrons or just tons of EM radiation which is what I focussed on.
That sturdiness of the cladding things is an important factor when it comes to making cost-effective reactors, that is, the price you sell electricity for needs to cover replacement parts, but is not really that much of an issue when it comes to achieving fusion the materials we have are sufficient for that. Proxima Fusion (the Max Planck spinout) is working on those economical issues for their commercial prototype (early 2030), it remains to be seen whether they go for durable and expensive or cheap but needs to be replaced more often. Which isn't unusual for power plants in general, none of them run 24/7 they get shut down for maintenance once in a while.
I'm aware (I read the article, including the part I quoted you), but regardless of the source of the melting, there is a melting issue of the containment vessel that needs to be engineered away.
Yes, and you won't get me to argue here. I'm too experienced a smart-Alec to contradict another smart-Alec :)
Well I'll take smart alec over being called pedantic any day.
Having said that, sincerely wasn't looking for the argument, just a matter of going back to my original point, that you corrected and educated me on.
I knew there was some kind of melting issue, when I had made my original comment. I had just assumed it was the plasma, but it ended up not being that, as you noted.
My follow-up link comment was just to say "Hey look there is a valid reason for melting to happen, I wasn't imagining it".
All's good on my end.
How are they even containing that heat as this is obviously warm enough to melt everything in existence (as far as I know)?
vacuum for isolation. Magnets, so the plasma stays in the middle and won’t touch the walls. Microwaves to heat it up from the outside.
ELI5 would be huge magnets. If there is something that melts everything humanity ever created and knows of, keep it away from everything. But it is a real problem, instability in the plasma leads to the need for better materials.
https://en.m.wikipedia.org/wiki/Nuclear_fusion
The fusion of light elements up to a certain nucleus size releases energy. However, fusion only occurs at very high temperatures and pressures. The goal is to 1) create the conditions for nuclear fusion (which they did), 2) have the fusion reaction produce energy that sustains those conditions (they did for 48 seconds), and ideally a tiny bit more, 3) gather residual energy that isn't critical to the reaction itself, which is the part that looks like a steam engine.
presuming you mean a fusion electricity power plants - maybe. That's one option.
at those temps, thermoelectric could be interesting.
https://en.wikipedia.org/wiki/Thermoelectric_effect
Sorry im not any sort of scientist here but i thought energy could not be created or destroyed so to get a net-positive energy out we would need to keep feeding in fuel, is this correct?
And if so, how?
energy is not created nor destroyed, however something can change forms, which gives off energy.
how stars work in fusion is that their high pressure and high temperatures allow for the fusion of particles. hydrogren (1 protonl fuses with another to produce helium (2 protons). in a stars life, that cycle continues. elements fuse till it hits iron (the end point of fusion). which then a stars life.is considered dead and eventually black hole stuff starts to happen due to density of star.
the power is actually not "infinite" its limited by the fuel supply available (hydrogren), but the net energy in to energy out is positive if the fuel source exists.
Yes but how do you keep feeding this kind of reaction? I imagine you cant just drop more fuel 'down a tube'. Do they shut down the reactor and then restart it with fresh material?
I assume they shoot the fuel in with some light particle acceleration. Maybe they just let it diffuse in, but it's a gas so it's not that hard to get it to enter.
The hope is they get the cost of maintaining the electromagnets (power and cooling) to be cheaper than the power we can extract from the reaction.
My question is more about what's the logistics of getting power out? We're making a lot of heat, so it's probably steam power at the heart of it, but a lot of this effort is to keep the heat in is it not?
I’m not an expert but I believe the fuel is hydrogen. Hydrogen atoms fuse together to produce helium + energy