11–20 of 21 posts
wasn't some form of graphene superconductive at room temperatures? Is it possible to turn that into a coil - superconductive at room temperatures?
I don't think graphene was superconductive until this lithium method was discovered or maybe this allows it to be super conductive a a higher temperature.
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Maybe that's an entirely stupid question and please overlook my complete ignorance in this matter, but it certainly sounds quite challenging to keep a superconductor at around -190 deg C while just some feet away there is confined hot plasma at millions deg C. Would this be a problem?
Not a stupid question at all. One could say the foundations of the entire ITER programme circle around need to answer that one. :) [0] But on a more practical note: the containment for the plasma is a vacuum. All the matter inside the magnetic container is held within the plasma, and in simplified terms, between the "surface" of the plasma and the wall of the container there is _nothing_. Vacuum is a very good insula…
The image appears to be from 2012. The current funding is 'fusion never'. I hope that's not true.
Earlier quoted context omitted.
Maybe that's an entirely stupid question and please overlook my complete ignorance in this matter, but it certainly sounds quite challenging to keep a superconductor at around -190 deg C while just some feet away there is confined hot plasma at millions deg C. Would this be a problem?
Not a stupid question at all. One could say the foundations of the entire ITER programme circle around need to answer that one. :) [0] But on a more practical note: the containment for the plasma is a vacuum. All the matter inside the magnetic container is held within the plasma, and in simplified terms, between the "surface" of the plasma and the wall of the container there is _nothing_. Vacuum is a very good insula…
Someone posted this the other day (apologies, I can't remember who). http://i.imgur.com/sjH5r.jpg The image appears to be from 2012. The current funding is 'fusion never'. I hope that's not true.
Earlier quoted context omitted.
Not a stupid question at all. One could say the foundations of the entire ITER programme circle around need to answer that one. :) [0] But on a more practical note: the containment for the plasma is a vacuum. All the matter inside the magnetic container is held within the plasma, and in simplified terms, between the "surface" of the plasma and the wall of the container there is _nothing_. Vacuum is a very good insula…
Very interesting. What about the high-energy neutrons produced by D+T fusion though? Wouldn't they escape the magnetic containment?
They are also a major source of excess energy once the reaction becomes self sufficient. Capture the high-energy neutrons in a suitable material and it heats up. Use heat exchangers to run turbines, produce electricity.
If you read up on fusion energy, you'll soon encounter the note that fusion reactor waste is short-lived and therefore easier to manage + store than fission reactor waste. The material used to capture neutrons is transmuted to radioactive isotopes, but due to the choice of materials* used the half-life of those isotopes is pretty low.
Yes, it also means that the fusion reactor waste is more energetic and more active radiation source than fission waste. But because it's going to become safe in just a couple of hundred years, it causes much less of a headache in terms of storage.
*: We don't necessarily know what the radioactive isotopes will be. I think the jury and researchers are still out on that one but I dare say it's guaranteed that the neutron absorbent will NOT be uranium or radium.
Earlier quoted context omitted.
Very interesting. What about the high-energy neutrons produced by D+T fusion though? Wouldn't they escape the magnetic containment?
Yes. They are also a major source of excess energy once the reaction becomes self sufficient. Capture the high-energy neutrons in a suitable material and it heats up. Use heat exchangers to run turbines, produce electricity. If you read up on fusion energy, you'll soon encounter the note that fusion reactor waste is short-lived and therefore easier to manage + store than fission reactor waste. The material used to ca…
At this point, I was also wondering if you have any idea about how much of the heat transfer from the plasma to the vessel would be be through those neutrons (ie if it's the main heat transfer medium).
Earlier quoted context omitted.
Yes. They are also a major source of excess energy once the reaction becomes self sufficient. Capture the high-energy neutrons in a suitable material and it heats up. Use heat exchangers to run turbines, produce electricity. If you read up on fusion energy, you'll soon encounter the note that fusion reactor waste is short-lived and therefore easier to manage + store than fission reactor waste. The material used to ca…
To clarify, when talking about the neutrons I wasn't thinking about the radioactive waste problem, but about keeping the superconductor's temperature low. I just took a look at the Iter schema and noticed that there is a "blanket" that covers the interior surface of the vacuum vessel exactly to absorb the neutrons. The vessel then has a water cooling system. At this point, I was also wondering if you have any idea ab…
I found one fairly decent source [0] which goes into somewhat greater detail. It's worth noting that if you follow the link to first page of the series, that page explicitly states that what fusion reactors call "neutron flux" would be called "heat flux" in traditional reactors.
And it makes sense even when thinking logically. Energy and matter are interchangeable, and the reactor turns matter into energy; majority of matter escaping from the fusion reactor will be helium and neutrons. These particles interacting with external solid matter turns kinetic energy into heat. That's the power plant's heat source.
Now, as to the fraction of heat transferred by neutrons compared to that transferred by the newly formed helium - I have no idea.
0: http://www.visionofearth.org/industry/fusion/how-do-we-turn-...
Earlier quoted context omitted.
To clarify, when talking about the neutrons I wasn't thinking about the radioactive waste problem, but about keeping the superconductor's temperature low. I just took a look at the Iter schema and noticed that there is a "blanket" that covers the interior surface of the vacuum vessel exactly to absorb the neutrons. The vessel then has a water cooling system. At this point, I was also wondering if you have any idea ab…
By my understanding practically all of the generated energy is due to neutrons hitting the containment vessel. Highly energetic neutron, impacting solid matter, will generate quite a bit of heat in the violent collision. I found one fairly decent source [0] which goes into somewhat greater detail. It's worth noting that if you follow the link to first page of the series, that page explicitly states that what fusion r…
Regarding helium, considering that it's plasma we're talking about, I think it can't escape at all - the separated nuclei and electrons should be contained by the magnetic field.
https://en.wikipedia.org/wiki/National_Ignition_Facility
For more links and my modes overview of the project see http://blog.ehuna.org/2009/05/national_ignition_facility_192...
