Ahhh the American Hiroshima scare rises again. Seems it comes up every 6 months or so with whatever is the latest concern. Last time it was Ramadan....oh yes we are going to get nuked at Ramadan.
Farah gets a lot mileage out of this crap, over and over again, and those not paying attention get duped over and over again.
American Hiroshima is horsecrap....we can attack Iran at our leisure.
Gotta tell ya, that's not how I understand things.
First, there is some "minimal" amount of material underwhich, a chain reaction cannot be created/maintained. (This reaction is what causes nukes to go "boom.") Although said material is not the only component to any bomb, it is sufficiently small that it could readily become a "suitcase" sized bomb. Remember, we had mass quantities of nuke artillery shells. Bigger than breadbox, yes, but much smaller than a footlocker (not to mention, two). Each a completely self-contained bony-fidy nuke.
Are there such things? Beats me, but they are emminently feasible. And that minimal amount is small enough that it could be readily exceeded (for engineering safety/viability margins) and still qualify as "suitcase" sized.
Secondly, nuke maintenance. Fascinating subject, one with relatively few experts. And they're not sure. Unclassified sources have claimed life span of a non-minimalized (so there's a safety margin of material that'll go boom, when required) at about 29 years. Which creates a whole slew of strategic issues/questions, given that Clinton essentially closed our last plant.
My understanding, however, is that recent attempts to verify/refute that 29 year number leaves the question somewhat open. Apparently some nukes checked were still good. So the true experts are back examining their models and numbers to see what the real figure should be.
To return to the "suitcase" maintenance issue...bottom line is we don't truly know how they were all made (if at all), don't truly know what their life-span would be (for same reason), and so cannot reliably conclude they "cannot exist." They could exist. And last I checked, no one sufficiently intelligent to make one, had made one such that it would have to be used within 1-5 years or be useless.