> And you are entirely wrong about the isotopes of hydrogen. Tritium is highly radioactive, with a half life of ~12 years. And it is not just hard, but virtually impossible to isolate tritium out of water.

On the contrary, it's quite easy to do if there is any significant fraction of tritium present. The proportional mass difference of ³H vs. ¹H is x3, which alters the chemistry enough to make separation easy. You can use fractional distillation or electrolysis even for ²H — even mere hobbyists involved in the DIY fusion reactor scene sometimes extract deuterium from water this way, tritium would be easier.