Look, I want to agree and I'm neither a geologist nor a nuclear scientist but I think you're fantasising if you think there will be no particulate, dispersed matter. The salt mix even if the lower temp melting mixtures is 200°C or more above ambient. It will explode on contact with moisture. There will be clouds of burning materials.

If you say LESS dispersed radiation? Sure. None... sorry not chemically or mechanically or hydraulically or meteorologically plausible.

The elephants foot degrades over time into dust. Radiation causes stress fractures in solids, crystalline structure disturbs. It's going to "decay" in the non radiative sense of the word.

Btw I am pro nuke, in Hypothesis. In my economy (oz) it would have been ideal 30 years ago. Now, with zero power nukes (only one medical manufacturer with a dido type swimming pool reactor) the build out is probably economically infeasible after lawsuit attack, compared to solar, wind and battery. But I remain hopeful of this new stuff, and the PBMR