A nuke in a shipping container would need to be heavily shielded or it would be detected.
Trouble is it is easy to scan to see if any containers on a ship have shielding since a low-level neutron source could not pass through the container.
A nuke in a tank of water would be shielded by the hydrogen atoms.
On a Mars mission the crew would take refuge in a small shielded space inside their water supply in case of a solar flare.
A possible horror story would be to place a nuke in the center of a cement mixer tank and fill it with water...then just drive to the target :-(
“A possible horror story would be to place a nuke in the center of a cement mixer tank and fill it with water...then just drive to the target :-(”
Probably wouldn’t be too difficult for them to sneak small nukes in from Mexico or Canada, or even on a small boat. Once they get them near the intended targets the shielding can come off. The possibilities grow from there. Bring one up a tall sky rise, or load them onto private planes, or go real low tech and use hot air ballons.
Even a dirty nuke?