The plan is for them to breed their own tritium, though, so the consumables coming in the front door would just be deuterium and lithium, both of which (while less common than tap water) are not rare.
My understanding (and I am a layman) is that lithium isn't that accessibly common on Earth, and that we're doing a bang-up job of using as much of it as we can get our hands on already. Are there practical methods of extracting less accessible lithium that don't themselves have nasty side effects?
