"And such a beast has existed since the 1960s, funded by the USAF."
"Lookup the Oak Ridge Experiment."
I'm aware of it, along with their design plan for a full size MSR reactor in the GW range, and it's industrial support.
Sadly when the USG decided to look at alternatives they went all in with the Sodium cooled fast breeder concept.
Which has worked out so well for all concerned.