[pfdietz]

TRISO increases fuel cycle costs. It's harder to make, harder to dispose of, and (IIRC) uses higher enrichment.

[ggm]

The positive schpiels say it gets higher utilisaton ("burn") of the fuel inside the micropellets, so it may be HEU, but there's more taken out so less made overall.

I'm unsure where the H in HEU comes from, probably nasty sources, and probably nasty radiochemistry.