That's a very optimistic view of humanity that I can't say I share. If you give a sufficiently motivated person enough isolation and time, they can cut into just about anything. And possibly deal with cleaning up the results of any internal tamperproof countermeasures. In a world that contains people like the Las Vegas mass shooter or those who conducted the 2015 attacks in Paris, handing out isotopes to the ordinary person seems like a recipe for disaster.
We live in a world where multiple people are killed every year by tipping vending machines over onto themselves and you propose to make nuclear reactors a mass market consumer good that goes in everyone's garage?
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.
> because there is no realistic path for nuclear reactors to compete with PV+batteries
It's not that in Northern climates, it's PV+batteries+Natural Gas turbines, because PV doesn't supply enough power for winter heating. In more tropical locations, you're correct.
We live in a world where multiple people are killed every year by tipping vending machines over onto themselves and you propose to make nuclear reactors a mass market consumer good that goes in everyone's garage?