Comment by westurner
4 days ago
> 1337 seconds
AFAIU, no existing tokamaks can handle sustained plasma for any significant period of time because they'll burn down.
Did this destroy the facility?
What duration of sustained fusion plasma can tokamaks like EAST, WEST, and ITER withstand? What will need to change for continuous fusion energy to be net gained from a tokamak or a stellerator fusion reactor?
If this destroyed the facility that would be the headline this news article.... WEST highest is 22 minutes (it's in the title) and you could google EAST and ITER but the title tells you it is less than 22 minutes. WEST is a testing ground for ITER. The fact that you can have sustained fusion for only 22 minutes is the biggest problem since you need to boil water continuously because all power sources rely on taking cold water and making it warm constantly so that it makes a turbine move.
there is destroyed and then there is a smoking hole in the side of the planet:) but I think it fair to say, that after 22 min running, that there is no way that it can be turned back on later kind of thing, fairly sure its a pwhew!, lookatdat!, almost lost plasma containment.... keep in mind that they are trying to replicate the conditions found inside a star with some magnets and stuff, sure its ferociously engineered stuff but not at all like the stuff that could exist inside a star so all in all a rather audacious endevour, and I wish them luck with it
The system is not breakeven and the plasma was contained for 22 minutes so the situation would be the plasma was contained until it ran out of fuel. It is made out of tungsten for heat dissipation, has active cooling, has magnetic confinement with superconductors to prevent the system from destroying itself. https://en.wikipedia.org/wiki/WEST_(formerly_Tore_Supra)
1 reply →
To rephrase the question: what is the limit to the duration of sustained inertial confinement fusion plasma in the EAST, WEST, and ITER tokamaks, and why is the limit that amount of time?
Don't those materials melt if exposed to temperatures hotter than the sun for sufficient or excessive periods of time?
For what sustained plasma duration will EAST, WEST, and ITER need to be redesigned? 1 hour, 24 hours?
The magnets in the device make the plasma be in a doughnut like shape to prevent it from touching the rest and it has active cooling, the parts that are around the plasma are made out of tungsten to dissipate heat. The sustained plasma duration would have to be turned on for as long as a traditional power generation device like a fission reactor or an oil / coal power station.
EAST, WEST, URNER
2 replies →
> all power sources rely on taking cold water and making it warm constantly so that it makes a turbine move.
PV (photovoltaic), TPV (thermopohotovoltaic), and thin film and other solid-state thermoelectric (TE) approaches do not rely upon corrosive water turning a turbine.
Turbine blades can be made of materials that are more resistant to corrosion.
On turbine efficiency:
"How the gas turbine conquered the electric power industry" https://news.ycombinator.com/context?id=38314774
It looks like the GE 7HA gas/hydrogen turbine is still the most efficient turbine? https://gasturbineworld.com/ge-7ha-03-gas-turbine/ :
> Higher efficiency: 43.3% in simple cycle and up to 64% in combined cycle,
Steam turbines aren't as efficient as gas turbines FWIU.
/? which nuclear reactors do not have a steam turbine:
"How can nuclear reactors work without steam?" [in space] https://www.reddit.com/r/askscience/comments/7ojhr8/how_can_... :
> 5% efficient; you usually get less than 5% of the thermal energy converted into electricity
(International space law prohibits putting nuclear reactors in space without specific international approval, which is considered for e.g. deep space probes like Voyager; though the sun is exempt.)
Rankine cycle (steam) https://en.wikipedia.org/wiki/Rankine_cycle
Thermoelectric effect: https://en.wikipedia.org/wiki/Thermoelectric_effect :
> The term "thermoelectric effect" encompasses three separately identified effects: the Seebeck effect (temperature differences cause electromotive forces), the Peltier effect (thermocouples create temperature differences), and the Thomson effect (the Seebeck coefficient varies with temperature).
"Thermophotovoltaic efficiency of 40%" https://www.nature.com/articles/s41586-022-04473-y
Multi-junction PV cells are not limited by the Shockley–Queisser limit, but are limited by current production methods.
Multi-junction solar cells: https://en.wikipedia.org/wiki/Multi-junction_solar_cell#Mult...
Which existing thermoelectric or thermopohotovoltaic approaches work with nuclear fusion levels of heat (infrared)?
Gas turbines are more efficient than steam turbines simply because they can be used at higher temperatures.
However the exhaust gas of a gas turbine will still contain a great part of the input energy.
Therefore in order to reach maximum efficiency in a power plant, you must start with a gas turbine, which must be followed by a cascade of 2 or 3 steam turbines that run at lower and lower temperatures (this combination of a gas turbine with some steam turbines is what "combined cycle" means), until you obtain exhaust steam that is not much hotter than ambient temperature, and which can be used for heating, to recover even more of the input energy than what has been converted into electric energy.
Instead of gases or steam, turbines may also use supercritical fluids, e.g. carbon dioxide, which may lead to using less turbine stages and with much smaller turbines (that must work at much higher fluid pressures).
A gas turbine that is used alone, without steam turbines that recover the heat from its exhaust gas, has normally a too low efficiency. Its use can be acceptable only for mobile generators or emergency generators, where the size and complexity are more important than the efficiency.
Okay so I meant to say the simplest way is to heat water in this situation. But there are alternatives here https://en.wikipedia.org/wiki/Fusion_power?wprov=sfti1#Tripl...
1 reply →
> Multi-junction PV cells are not limited by the Shockley–Queisser limit, but are limited by current production methods.
Such as multilayer nanolithography, which nanoimprint lithography 10Xs; https://arstechnica.com/reviews/2024/01/canon-plans-to-disru...
Perhaps multilayer junction PV and TPV cells could be cost-effectively manufactured with nanoimprint lithography.
There is no danger of destroying the facility. The problem is keeping the plasma going. Even with self-sustaining fusion, the plasma doesn't have that much energy, it is really hot but low density.
The duration is because plasma is heated by rising current, and that hits limit after some period of time. With self-sustaining fusion, heating shouldn't be needed after the initial pulse.