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What about degradation of superconducting materials under high neutron flux which will be generated by a "commercial" load? IIRC modern superconducting material
by fuoqi 6y ago
What about degradation of superconducting materials under high neutron flux which will be generated by a "commercial" load? IIRC modern superconducting materials rely on relatively fragile meta-structures, which can be easily damaged by a sufficiently strong radiation. Changing magnets one-two times per year does not sound good for economic viability of such reactors.
- willis936 6y agoNeutron flux at the coils is one of the primary things looked at in reactor studies. It is a factor in choosing the thickness of the lithium blanket and boron coating.
- dogma1138 6y agoThe lithium beryllium molten salt they’ll use as a coolant and useful heat extractor should be enough to capture free neutrons. It’s the same mixture that is used in molten salt fission reactors so it’s neutron absorption profile of it is well understood. As a bonus you should be able to extract tritium from the molten salt which means it will produce some of its fuel too so it’s a partial breeder reactor too.
- elihu 6y agoI think if I understand correctly, there'll be a fluid (FLiBe) between the plasma and the magnet coils that absorbs most of the neutrons. The FLiBe heats up and is used to boil water to power a steam turbine. SPARC isn't particularly designed for durability, but for the ARC reactor which is meant to be the commercially-useful iteration they're looking at having solder joints on the superconducting magnet film so the whole top of the reactor can be removed so they can pull out the inner lining in one piece and replace it. (Apparently they figured out that regular non-conducting solder joints don't actually introduce very much resistance.) I don't think there's any plan to replace the ribbon.
- jacquesm 6y agoregular non-superconducting solder joints. They conduct, just not nearly as good as the material itself at that temperature. Still, interesting that that would not result in enough power to boil away the solder.
- elihu 6y agoYeah, that's what I meant. Thanks. I guess if the solder joints are super-thin, there isn't much resistance. But still, it defies intuition. One of the other weird things the MIT group working on SPARC has been experimenting with that sounds like it totally wouldn't work but apparently it does is that they don't bother to insulate between the Rebco tape windings. The superconductor is just a thin layer on top of stainless steel, and the stainless steel is a sufficiently mediocre conductor that the vast bulk of the power takes the long way around following the superconductive layer rather than taking a shortcut through the stainless steel. Apparently the insulator is less durable than the tape itself, so not having to rely on it makes for a more durable device.
- NortySpock 6y agoHuh. I would have assumed kapton tape wouldn't have been too hard to add, but if you can do just fine without that, it's even fewer manufacturing steps.
- jamiek88 6y agoThe best part is no part!
- anonuser123456 6y ago>IIRC modern superconducting materials rely on relatively fragile meta-structures The HTS 'tape' they use is very robust. A lot of the work they are doing is qualifying the coils and magnets under various scenarios.
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