Interesting concept. Of course, the first thing that comes to mind is how to protect these units from the bad guys.
If you mean "protect these units from bad guys so they don't steal the thorium and weaponize it," that's one of the great things about thorium reactors: thorium and its byproducts are very hard to weaponize. [1]
[1] https://en.wikipedia.org/wiki/Liquid_fluoride_thorium_reacto...
Sure, the U-232 contaminated U-233 is nasty, but as long as it doesn't make it impractical to make a nuclear warhead it's quantitatively different from the uranium cycle, where after a few months at most plutonium is impossibly contaminated with two even more undesirable isotopes (one is very hot, I've seen estimates of 100kW for a bomb sized quantity (it's used for RTGs in deep space probes), the other precludes much of a bang and required the Manhattan Project to go with an implosion design).
Despite the gamma ray emission drawbacks, it could still be the easiest way to get lots of weapons grade fissionables from civilian power plants.
Reduces to a protoactinium problem, it decays to U-233 with a half-life of 27 days. The article claims there's so little protoactinium in the total mass of salt and stuff that it's not practical to isolate it, at least not without detection, and failing that, not quickly. This gets into fine details beyond my level of expertise, but I agree the problem is much reduced. Although very possibly still greater than for current LEU designs.
Solid thorium reactors mix Th with the existing waste piles of Plutonium sitting in cooling pools and burn that up for us[1].
There's no waste materials to release from either of these reactors.
[1] http://www.extremetech.com/extreme/160131-thorium-nuclear-re...
These reactors by definition have a fair amount of very "hot" materials; it hardly matters if none of them are declared "waste" if they'll still kill you in a few minutes of direct exposure.
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.
(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.)
There could be a risk of contamination from the cooling loop, but such contamination might even be less than the normal radioactive fallout from the flues of coal plants.
Petrol from a tanker? Shaped charge.
Cracking armored vehicle? Shaped charge.
Unlocking stuck door? Shaped charge.
It really does seem people try to downplay any potential reactor designs because global thermonuclear war may damage the reactor. Stop living in fear.
The radioactive fuel is a molten salt, so it will cool and solidify soon after dispersal. It is certainly not good, but is it really worse than say, a chemical plant?
The radioactive stuff won't remain airborne after the initial blast, so that means a predictable and small area to remediate.
The fuel dispersed in an explosion can be collected, since it will solidify, so it won't poison the water table.
While not perfectly safe (nothing is), the disaster contingencies seem fundamentally different and better than those from a PWR + solid nuke waste disposal site.
There would be many more of them, which is both good and bad for various cases.
If you have a lot of units, the loss of one or a few has limited effects, vs. taking out a few big baseline power plants and/or major transmission nodes.
What's the local/regional cost if someone takes out a node with a sufficiently big shaped charge?
You make things because they are interesting to make, and could have a positive impact in the world. Protecting yourself from "the bad guys" is a secondary (or even tertiary) concern, unless the very purpose of the thing is to protect people from bad guys (for example a military fort).