I've been thinking about the dumb idea of using solid uranium/thorium as the (closest) salt containment layer: you have a solid uranium (melting point 2000C) or thorium layer (3000C) around the salt, which may not degrade it that quickly if the salts (which are a solution basically, if it's a liquid?) are more or less saturated. Or even if it isn't, how long would a layer of uranium or thorium last? I guess that's the big question.

You don't care if the thorium or uranium captures neutrons I would think. Thorium neutron capture is a good thing.

So depending on how long the solid "breeder" inner shell hold up, when you "recondition" the inner shell, I assume you can just dissolve it into salt, feed it into the normal fission products processing that the salt fuel use, and put in a new solid uranium/thorium salt shell.

Or maybe thorium could be alloyed for more endurance properties as the containment. Of course I have no idea about the various cracking / strength / fatigue properties of thorium as a metal.

I wonder if pellets/spheres could use thorium as a surrounding material.

So how nuts is all of that?

Maybe you could do a weekly monthly re-coat of the inner layer with more thorium or uranium to replace that which gets dissolved/degraded.

Edit: ORNL on thorium properties in a nuclear environment

https://www.osti.gov/servlets/purl/4622065