[iso1210]

Smallest nuclear bomb (not dirty bomb) made was 23kg, literally suitcase size. However if you have one and want to use it, you're probably better off sending it in on a shipping container or truck (or commercial or private plane)

[treeman79]

Lots of detectors for those. Not sure how extensive, but it’s a known attack vector.

Apparently it’s hard to fully shield weapons grade material