Hobo wrote:

Even worse, imagine a bunch of people in a basement working on a gun
device nuke. When ready they set a timer and leave the city. If the
device doesn't work they return to make ready a second attempt and keep
doing so until they succeed.

Anyone with the resources to get a big chunk of fissionable material
shouldn't have to muck around too much with making it work.

The world has been really fortunate that most of the really nasty folks
- the sort that would happily detonate such a weapon - are too dim to
manage something that complicated.

Our first warning that a terror organization has a big chunk of
fissionable material will probably be radiation detectors going off well
downwind from an accidental critical mass.

--
cirby at cfl.rr.com

Remember: Objects in rearview mirror may be hallucinations.
Slam on brakes accordingly.