Regulation is a serious barrier in the U.S. but Canada is a lot more rational about new technologies.

Simple answer to "why not solar" is that we need power at night, and it's not clear that storage at large scale would be cost-competitive with molten salt reactors. (I think nuclear baseload with solar for extra daytime load makes a lot of sense, though.)

I once described molten salt reactors to a very anti-nuclear activist in the Green Party, and he said "hmm...that actually sounds pretty good."