[DennisP]

They say they'll use pure lithium but I don't see how that can work. One lithium nucleus plus one neutron makes one tritium nucleus. If you lose any tritium at all, you run out after a while. Other fusion projects include lead or beryllium, which releases two neutrons after getting hit by one. That keeps their tritium breeding over unity.

On top of that, First Light says they'll use natural lithium without enriching it to lithium-6, which makes things even worse.

[pencilguin]

If they used 50% enriched 6Li/7Li, they would breed extra tritium. But there would be no point, because they would have no way to refine it out. They don't care, because they know there will never be an actual power plant. They will spend investors' money, have some fun, and move on.

[dotancohen]

  > But there would be no point, because they would have no way to refine it out

Why not? I'm not a subject manner expert, but from my armchair it seems that refining one element from another is far more straightforward than refining one isotope from another as is done with Uranium.

I would expect that hydrogen and lithium should be able to be refined chemically, as both are very reactive elements. And even if mechanical refining is necessary, we have much industry experience with that: Uranium isotopes have been mechanically refined for almost a century. Furthermore, lithium and hydrogen are far more dissimilar than are U235 and U238 - lithium has six times the atomic weight of standard hydrogen and double the atomic weight of tritium.

[pencilguin]

See, this is how they find pigeons to hand over all their money.

[DennisP]

"Gee that guy made a good point...I don't really have an answer...I know, call him a pigeon!"

[sbierwagen]

Heavy water reactors have been producing tritium at scale for decades. India is talking about deploying a bunch of new PHWRs. They're recovering tritium from water, obviously. Would it be much harder to recover it from molten lithium? (Lithium hydride complexes?)

[DennisP]

Seems like a hydrogen gas in a vat of liquid metal or salt is just going to just bubble right out.

[pencilguin]

At PPB concentration?

Literally anything can seem, to somebody.

[DennisP]

I guess literally anything can be "PPB concentration" if you don't care how many parts it is per billion.

A 1GW fusion reactor would consume about a ton of fuel per year.[1] That's about 600 kilograms of tritium. Over the course of the year a reactor with a positive breeding ratio will produce more than that.

The breeding blanket for ITER will be about 2000 tons[2] and ITER is designed to produce 500MW.[3]

This means that ITER will produce at least 300 kg tritium in 2000 tons of blanket, over the course of a year. Collect the tritium annually and you've got a concentration level of 150 parts per million, or 150,000 PPB.

[1] https://ccfe.ukaea.uk/fusion-energy/fusion-in-brief/

[2] https://www.iter.org/mach/Blanket

[3] https://www.iter.org/proj/inafewlines

[pencilguin]

You need to get that tritium out every day to have something to operate the reactor on. Look up the worldwide stock of tritium sometime.