[neutronicus]

Your zeroth-order mental model of a Thorium reactor should be "exactly like a Uranium reactor". It's a different radioisotope; it ain't magic.

[DennisP]

Your first-order mental model should be that (1) thorium requires breeding and that works in a thermal spectrum, (2) uranium doesn't require breeding if you're content with fissioning U235, and (3) you can have a breeding uranium reactor but that requires a fast spectrum.