First: microwaves are only safe if you don't mess with them, a bunch of people get killed by tinkering with their high-voltage transformers (at least 35 US deaths from one specific usecase alone in the last decade, see https://www.woodturner.org/Woodturner/Resources/Safety-Mater...).

A big potential concern with small reactors are highly toxic radionuclides; those can be much more dangerous (with LD50 far under 1mg/kg) than "ordinary toxins" like bleach or even nasty stuff like methyl isocyanate. That means expensive disposal and protection measures.

All of this is a non-concern though because there is no realistic path for nuclear reactors to compete with PV+batteries, ever. With cells already <$100/kWh and the panels being cheaper than glass windows, we will never be able to build, maintain and dispose of nuclear based reactors tech at a competitive price point, especially not with the insane current battery demand (automotive) driving technical optimisation and price competition.