Back in the '80s, a pair of HTGCRs (High Temperature Gas-Cooled Reactors) were proposed in the US (Arizona, IIRC). They were also based on the Thorium cycle. Advantages included inherent safety - they shut down when they lost coolant gas (I don't recall what gas was used, but likely Helium). They were never built, probably as a result of the 3-Mile Island mishap.
https://www.alternative-energies.net...actors-energy/