I didn't realize that the viscosity stays high for molten salt[1], that makes everything abrasive, along with dealing with possible phase change if the salt solidifies... yikes!

So, what we're dealing with is highly radioactive corrosive molasses with a constant stream of radioactive decay product gasses bubbling out of it, like Xenon and Iodine. Yeah, that seems more challenging that I first thought.

  1 - https://www.powermotiontech.com/home/article/21144640/armoring-a-valve-against-molten-salt