The problem is that none of these designs have ever been used to power the grid. Every nuclear project in the recent past has blown by cost and time estimates. Wind and solar are not only cheaper than nukes, they can also be installed much quicker and predictably. Nukes have a place, but we need clean energy now.
The US at least already has enough nuclear to handle base loads when solar and wind are unavailable. Nukes in some contexts are needed, but I believe we have 30% or so nukes in the US. Diverting resources to new nukes is a waste when we could be making carbon fuels unprofitable soon by investing in solar and wind.