Terrestrial Energy: The whole reactor, including heat exchanges and so on is defined for 7 years of life. After that a second reactor is running. After a few years the original reactor is put into a storage silo and then a new reactor is placed their ready to be switch to.
From memory they don't seem to pump the fuel from 1 to the other.
Flibe Energy: They are doing the famous lifter. Simular concept, 2 reactor cores with graphite moderation, after 7 years the fuel is pumped to the second reactor, the first is getting its graphite core replaced. This will have longer lead time to deployment.
Moltex Energy: They have totally different approach. Instead of 7 year lift-time they are building a traditional reactor with much longer life. They are basically building a sodium cooled fast reactor, but replace sodium with salt solution. And then in the fuel assemblies are also like those in sodium reactor, but contain liquid salt with uranium in them. They want to produce the fuel salt from spent Canadian CANDU fuel.
Kairos energy: This is a molten salt cooled reactor that uses pellet fuel but little balls instead of the traditional pellets.
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
So unless materials is solved, you need scalability and replacement. At least the OTHER problem with solid fuel, lots of waste, is generally not a problem with breeder reactors and liquids. You remove the fission products from the fluid and feed it back in. I'm no chemist so I don't know all the separation nastiness involved, but it's better than carting ten thousand year waste across the country to Yucca.
So the question is, what about the other reactor designs, don't they need replacement with respect to the vessel? And as I understand it, fusion reactors also have issues with high speed neutrons so their vessels would need periodic replacement, even if they get to sustained ignition and positive energy.
Your replacement containment layers seems like the "constant replacement" strategy. What if you could simply inject a new layer that hardens and pushes out the older layer?
Also, why not have solid uranium or some similar material as the inner container? Could simple saturation of the existing uranium in the salt prevent excessive wear?
I wonder how much of this approval is because the Chinese brought one online.