[pfdietz]

The ARC design (see https://arxiv.org/abs/1409.3540 for details) uses surprisingly little yttrium. The superconductor is only about 1% of the tapes, and the tapes are only a faction of the coils, and the coils mass is just a fraction of the mass of the coil support structure. I think the total amount of yttrium will be in the tens of kilograms, if that.

I have a suspicion that this is being funded at all because the magnet technology would be useful in non-fusion contexts (hybrid electric aircraft, superconducting generators in wind turbines.)

In contrast, IIRC a single ARC reactor of that design would have 90 tonnes of beryllium (although that could be reduced by half if the secondary loop used a different molten salt.)