The bigger problem than the corrosion is the inability to inspect the system in an efficient way. In a regulated nuclear industry, not knowing the status of the system means it will not be allowed.
Perhaps the NRC does require regular inspections for existing plants, but none of those existing plants are failsafe are they? If something starts to go wrong, it can snowball very quickly into a much worse situation.
With a MSR the worst-case scenario (short of terrorism) is that you empty into the dump tank until you sort the problem out and restart. If you make the entire facility's floor the dump tank then inspections are going to be rather redundant. Except perhaps to ensure that the dump tank is intact. But that can be made fairly easy I think.
See the quest for reusable launch systems like the space shuttle.
That is insane.
The best way to deal with waste is to recycle it.