[identity profile] fivemack.livejournal.com 2013-08-29 04:12 pm (UTC)(link)
Tritium has a 4500-day half-life, so exists on Earth only as the result of substantial technological intervention; since you need it to make H-bombs go off, the substantial technological intervention occurred. You make it by irradiating lithium rods in conventional fission reactors (the rods replace conventional control rods); proposed fusion reactors have a lithium blanket which both makes more tritium and provides some neutron shielding.

Production rates at present aren't great - 1.2 grams per rod in an eighteen-month cycle, 240 rods in the reactor at any one time, so about half a pound per year.

[identity profile] anton-p-nym.livejournal.com 2013-08-29 08:35 pm (UTC)(link)
Tangential point; CANDU produced enough tritium as a by-product of its PHR operations to support light industrial use back when I was a student. (IIRC, they had a nice sideline in self-illuminating EXIT signs.)

-- Steve's google-fu is weak today, else he'd provide reference links above.