Somebody should tell the NRC of this , because they had tested several 10;s of quite small nukes called "Appliances" at the Nevada Test Site about 90 Mi N of LAs Vegas, just N of Nellis AFB. These were about 100lb (43. kg)(Linear detonation rather than radial) devices that, still generated about 1kT, thats bigger than any truck bomb.Although even with 1 critical mass of Pu doesnt achieve big time fission multiplication due to the linear detonation shape and the minimal mass.
SO the "hollywood myth" does have some truth in it. The testing of "Appliances" (anything at 1 or 2 critical mass of fissionable material) was done at Nevada TEst Site in the 1970s and 1980's to determine the effects of EMP's on radios and TVs and even microwave ovens . There were several dug caves in a test area called "JAckass Flats" where several of the appliance test units blew the concrete plugs out of the caves and sent them on a quarter mile coontamination trip that turned the Flats into a rich harvest area of alpha particles.
Anybody who's worked in the arena can tell you about the possibility of suitcase newks. Even though that "Suitcase Nukes" are not the most efficient until they get about 3 or 4 critical masses in which to achieve fission multiplication , you can still get a nice bang in a city with 1 critical mass.(Itd be roughly 2 times the yield of Tim Mcveighs truck bomb) and if its with Pu, the alpha contamination would leave a large dead zone in the city that would need to be worked on by NEST teams for years and years. SO we only hope that the Jihadi design guys are less sophisticated in the trigger depts and a couple other areas that are important to get some yield. WHen you talk about 4 or 5 critical masses , you dont need to worry about clandestines and using "suitcases or briefcases". You could assemble a shaped radial detonation and put it together in various areas and assemble it in a crew cab pickup bed.