Is there any of these built as a real world test?
Yes, but I couldn't reemember what thread it was on, mine or someone else's. Fortunely, I checked thorium as a keyword, and someone gave me a Wikipedia reference, although I read it somewhere else. If you go down to Thorium as a nuclear fuel, then you'll find at the end of the first paragraph:
One of the early pioneers of the technology was U.S. physicist Alvin Weinberg at Oak Ridge National Laboratory in Tennessee, who helped develop a working nuclear plant using liquid fuel in the 1960s.P.S. Wikipedia is a decent source when the subject isn't political.