How to extract bred tritium at parts-per-billion concentration from hundreds or thousands of tons of "blanket" material quickly enough to cycle back into the pl

How to extract bred tritium at parts-per-billion concentration from hundreds or thousands of tons of "blanket" material quickly enough to cycle back into the plasma has not been studied, and might not be possible. Furthermore, nobody knows how to get enough tritium bred in it in the first place. You need for each neutron captured to breed more than one tritium nucleus, to make up for the fraction that fails to breed any. A fusion reactor with no fuel is a remarkably expensive doorstop.