Tritium has a half-life of 12 years so there is no deep pool of tritium upon which to draw. The primary source of tritium on earth is cosmic-ray interactions in the upper atmosphere that produces 7.5Kg of tritium a year worldwide.[1]

Isn't that going to cause a serious problem if it requires 323Kg/yr of tritium just to power New York City?

[1] https://www.sciencedirect.com/topics/earth-and-planetary-sci...

Apparently no, because it can be made by the fusion process itself, via contact with lithium, and there's enough proven reserves of the latter to supply us for 100s of years.

Nobody knows how to get tritium at PPB concentration from the thousand tons of radioactive molten FLiBe it is dissolved in. You have to process all of it every day because you need that tritium for fuel tomorrow.

I wonder if that is much or not. I have no idea how hard this is to produce. Do you have an idea about that?

Oooof, looks like the primary way of creating it is through... fission reactors.

https://en.wikipedia.org/wiki/Tritium#Production

And there's not much of it:

> According to a 1996 report from Institute for Energy and Environmental Research on the US Department of Energy, only 225 kg (496 lb) of tritium had been produced in the United States from 1955 to 1996.[a] Since it continually decays into helium-3, the total amount remaining was about 75 kg (165 lb) at the time of the report.

The concentration of deuterium in the ocean is about 150-160 parts per million and with 1233.91 quintillion liters covering the earth we have approximately 8.2260667e+12kg worth of it to extract, so we've got a bit to work through!

Tritium however is far more rare with only trace amounts of it being available within nature and barely more than a kg produced per year. Producing the 100s of kgs required per year still seems to be an unsolved problem, although my quick searching shows there's a couple viable solutions for it.

The solution is that fusion power plants can breed tritium and become net producers of it...

Though in practice enough will be lost that probably they'll still be somewhat net consumers-- just not nearly to the extent predicted by a simple thermodynamic model.

Still, even if fusion becomes a net producer of tritium, the whole tritium-is-hard-to-get problem will likely be a constraint that we'll be fighting as we ramp up use of fusion power in the future.

That such a small amount of matter could generate so much power is pretty remarkable. I might be way off base but from what I can find online it seems you'd need over 2000 times as much uranium?