They can use biomass made from pulped paper or non-toxic briquettes of hexane solid fuel.
No diesel to store. No dangerous flammables. In a pinch, will run from pulp bricks made from old newspapers.
They are also one-piece, modular and easy to situate in a dedicated room by themselves. Power output is pretty high for such a small device. Easy to exhaust through a positive pressure hatch aboveground.
Do you know, when I honestly consider it, I would rather have four of these in my shelter than my own molten salt reactor.
If your thorium generator broke down for some reason, how hard would it be to maintain or repair?
You could store enough safe inert fuel in advance to last a couple years and when it ran out, you could turn around and use compressed paper wads or even dried leaves, wood chips, or anything that burns.
Best of all, they produce clean hot water and can even be tapped for cogeneration to thermal heaters inside the shelter. Pretty hard to beat.