If someone siphons your gas tank, they're not going to be able to nuke Paris. But a nuclear pulse rocket needs thousands of bomblets the size of coke cans. That's the scary part.
> size of coke cans.
Not really, each one would be 6 inches in diameter and weight over 300lbs.
Dyson's book hints that they ended up far smaller, but the details of that are classified to the gills.
Sounds impossible. A 6 inch diameter uranium sphere is only 80 lbs, and there are no materials significantly denser than that.