Quercus wrote:Okay, so if the boron poisoning would work, the relevant question then becomes what is the optimal geometry to maximise plutonium to boron ratio and therefore expense?
And for extra credit, precisely how many government watch-lists will the googling to answer that question land you on?
Probably none, because you won't find anything. This is the part of nuclear weapon design that's still classified, and will probably always be classified. Figuring out the precise geometry necessary for optimal nuclear weapon design requires you to combine extremely advanced theoretical physics with direct access to numerous test results from Los Alamos or similar labs, using mathematical abilities of the highest order.
If a rogue government or group managed to get its hands on some weapons-grade fissile material, it wouldn't be terribly hard to use it to cause damage. At the very least, such a group could grind the fissile material into shrapnel and pack it around a few tonnes of conventional explosive to make a radiological dispersal device, to devastating effect. Or, as SFX linked
, 15-20 kg of weapons-grade plutonium could be placed in a Thin Man gun-type device with the full knowledge that it would fizzle (in comparison to true nuclear weapons) but still exceed its own weight in TNT-equivalent yield while maximizing fallout and radiological dispersal.
The only reasonable danger of rogue elements ever being able to produce a true nuclear bomb would be if they somehow got their hands on a couple hundred pounds of highly-enriched uranium (the type of uranium Iran has been trying to make for years). If that happened, they could construct a Little Boy assembly in any machine shop. In theory, it would be possible to build a true nuke out of 8-10 kg of weapons-grade plutonium by simply replicating the now-unclassified component design of the Fat Man or Trinity, but doing so would require access to a great deal of design and engineering and manufacturing expertise impossible without large-scale government funding. The North Korean government, which has access to ample weapons-grade plutonium and highly-enriched uranium from its dedicated reprocessing plants and centrifuge labs, was unable to manage more than a fizzle in its first nuclear test and only recently pulled off a 1-4 kt test.
Of course, in any of the above cases, it's delivery rather than design that poses the challenge. Crude nuclear weapons (or radiological dispersal weapons, either of the conventional-explosive or the nuclear-fizzle type) are huge, ungainly, and pretty much impossible for a rogue group to deliver to a target.
So yeah, none of that stuff is classified.
classified is the kind of stuff we're asking about in this thread, like the specific geometry to ride the edge of criticality, because that's what's required to manufacture highly-yield-efficient or ultracompact nuclear weapons. Like the W48 nuclear artillery shell
that's just 6.1 inches wide. Or the 105-mm nuclear artillery shell that physicist Ted Taylor claimed is possible. A 105-mm nuclear device is just 4.1 inches in diameter...that's incredibly small, roughly the same diameter as a roll of duct tape.
That's why all those tests at Los Alamos and elsewhere were necessary (including tickling the dragon's tail). The physics of chain reaction generations and critical-mass geometry is incredibly, fantastically complex and subject to many, many unknown factors. It took decades of testing and significant loss of life for enough experimental data to allow the world's most advanced nuclear physicists to precisely predict critical-mass geometry.
So we're never going to have an answer to "what is the highest possible plutonium to boron ratio in a size 11 shoebox" because there are only a handful of physicists in the world who would be able to answer that question, even if they had unfettered access to all the classified experimental data