Reflects a fundamental misunderstanding of the nature of explosive, atomic and thermonuclear weapons. Allow me to wax reflective; my grandfather started his war career at Pickatinny Arsenal and then ran the union at Los Alamos Scientific Laboratory where he befriended Norris Bradbury and Carson Mark. My parents met in Jr High there in 1953; both of them worked for the company until retirement (my dad still does, he's just a "consultant" now). Suffice it to say I grew up around this stuff. - For starters Conventional explosives of the kinds used by the major forces are stupendously stable. Dynamite evolved from nitroglycerin; TNT evolved from dynamite, PETN evolved from TNT, RDX, Semtex, C-4 and the other critters in the menagerie evolved from PETN. Everything from TNT onward is flame-proof, crush-proof and largely shock-proof. In order to set off the more stable explosives (IE, everything used conventionally today) you need an explosive priming charge. Seen Die Hard? Remember all the foofrah about "detonators?" If you stuff a firecracker in a block of RDX it might go off. No guarantees. Stuff a blasting cap in it and boy howdy. Note that blasting caps are also useful for blowing up stumps, which should give you an idea of the amount of shock necessary to fire conventional explosives. Note also that one of my grandfather's projects was a bomb designed to go off days, weeks or months after it was dropped. In other words, weapons designed in WWII could be forcibly ejected from a B-17 at altitude, crash through a factory, hit the concrete, and not blow up until the acetic acid phial in the nose eroded through the plexiglas disk to trip a chemical reaction that would set off said blasting cap a month later. Or, you know, until you tried to move it, in which case the mercury switch that suddenly came active as soon as it hit the dirt and settled would blow you to hell and gone (the Nazis got around this by using Jews to carry off the bombs). - Additionally The explosives necessary to trigger an atomic reaction must be stable enough to get chucked into a lathe or mill and machined. Granted, they do this under pretty specific conditions and granted, shit does blow up occasionally but to make the lenses necessary to concentrate a critical mass of weapons-grade plutonium into a fissile pile, an impressive amount of precision is necessary and that doesn't much happen by pouring. Which means, for those following along at home, that in order to get a dropped atomic bomb to go off by accident, not only must the conventional explosives be triggered (see above) but they must be triggered without warping the lens or else you just have a dirty bomb. Fat Man and Little Boy didn't just happen - those are precision devices. Smash a bunch of weapons-grade plutonium together and yeah, you'll get a bang... but if you want one of those good'n'proper "mushroom cloud bangs" a whole lot of shit has to go right all at once. - Finally It takes conventional explosives carefully arranged to trigger an atomic explosion. It takes an atomic explosion carefully arranged to trigger a nuclear explosion. The thermonuclear weapons we use today - and have since the '70s - I knew some of the guys who designed this thing backintheday - are miracles of precision. An atomic explosion is one thing. A nuclear one is entirely another. Even after Oppenheimer had the Manhattan Project in the bag, there was doubt as to whether or not a nuclear explosion was possible. In addition to actually working, these are devices that are designed to be fired out of a submarine at nine or ten G, lofted to just this side of the Karman Line (although that's mostly because of treaties, hurtled through the exact same re-entry that always looks so impressive in Apollo 13 and then right in the middle of that pesky, tumultuous process, triggered in such a way that the conventional, the atomic and the nuclear explosions all happen in the proper order. Hell, some of them are designed to do this after cleaving through 30 meters of concrete. _ _ _ So. Yeah, it's a good thing we haven't had any accidental nuclear explosions due to weaponry, but it's not like we haven't had plenty of opportunities. This is not due to luck, it's due to the fact that nuclear weapons are pretty goddamn tough.Anyways, it really is amazing that the world hasn't seen an accidental nuclear explosion yet. Let's hope we never do.