[tehwalrus]

...

molten salt reactors (the kind in the comment at the top of this thread) are at atmospheric pressure, and are designed with a drain plug which isolates the (very hot) materials from the neutron source, after which they cool down happily on their own in a separate but similarly shielded compartment.

release of materials is one of the most unlikely outcomes ever.

[hga]

You really can't imagine a release of materials outcome in the context of active sabotage?

(Which is relevant in the context of massive distributed ones; current nuclear power systems mitigate this by being few in number such that they can be well guarded.)

[tehwalrus]

since you can't weaponise the mixture, and it's just stupidly hot and dangerous for a while and then inert, I can't see why anyone would try to sabotage one. (apart from terrorists just out to cause mayhem, but that argument also works for cars, roads, planes, train stations, etc right?)