have you never heard of tamper-proof containers? mess with it, it’s useless and you go to jail for a long time?

Plus, they’re ubiquitous, you don’t know who has one, max damage is minimal even worst case — go fish!

We have microwave ovens. They’re pretty safe. Imagine something as safe as that. We can do it.

But I can’t disagree that it’s more exciting to imagine terror dreams.

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?