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Please don't try to store 600kg of U238 in a 1.11 cubic-ft container. That's just asking for it to go pop. Fissile material like that needs to be spread out, to

Please don't try to store 600kg of U238 in a 1.11 cubic-ft container. That's just asking for it to go pop. Fissile material like that needs to be spread out, to prevent any one lump becoming supercritical. See https://en.wikipedia.org/wiki/Nuclear_criticality_safety https://en.wikipedia.org/wiki/Nuclear_criticality_safety

mcv 5y ago
I would think it'd do a bit more than pop. They didn't spread it out over a bunch of trucks and three planes for nothing. Most of the weight is going to be secure containers, not the uranium itself.
systemvoltage 5y ago
No one is suggesting to put it in a small box and throwing it in the back of the airplane. It was to ascertain the readers with a mental picture of how much snuff we're dealing with here. Furthermore, it probably won't go pop, most likely fissile out into a dusty neutronic poof, not worth reporting to higher ups for obvious reasons. For a respectable, mushroom-cloud-worthy yield, you need to jam it in a rather serious reinforcement of Tungsten outer shell to make a weak gun-type bomb. It would still be unimpressive (thermo guys are gonna laugh at you), but hell of a lot better than stuffing it unintentionally in a small box. Safety is only important if there are further plans for survival, so it is sort of a moot point in this radioactive extravaganza. If you do happen to lose the material, be sure to have access to Tungsten as it is almost the same density (a tad bit higher than U238) and no one is going to notice it until we need to use it in the next war.
- mnw21cam 5y ago
  Agreed, pop is probably the wrong word. But if the demon core incidents are anything to go by [0], then I can well imaging an unsuspecting worker putting one more block of U238 onto a stack, and feeling a sudden wave of heat and seeing a flash of blue light. And then if they don't have the ability to shove the pile over into a more favourable geometry, seeing the whole pile start to melt into a puddle (which would thankfully also have a more favourable geometry). And then dying of acute radiation syndrome a week later. (Seriously, kids, don't try this at home.) Extreme heat will moderate the reaction to some extent, because the expansion of the metal means it is further apart and therefore has lower reactivity, however the temperature at which it stabilises could well be above the melting point of Uranium. [0] https://en.wikipedia.org/wiki/Demon_core https://en.wikipedia.org/wiki/Demon_core

mcv 5y ago

I would think it'd do a bit more than pop. They didn't spread it out over a bunch of trucks and three planes for nothing. Most of the weight is going to be secure containers, not the uranium itself.

systemvoltage 5y ago

No one is suggesting to put it in a small box and throwing it in the back of the airplane. It was to ascertain the readers with a mental picture of how much snuff we're dealing with here. Furthermore, it probably won't go pop, most likely fissile out into a dusty neutronic poof, not worth reporting to higher ups for obvious reasons. For a respectable, mushroom-cloud-worthy yield, you need to jam it in a rather serious reinforcement of Tungsten outer shell to make a weak gun-type bomb. It would still be unimpressive (thermo guys are gonna laugh at you), but hell of a lot better than stuffing it unintentionally in a small box. Safety is only important if there are further plans for survival, so it is sort of a moot point in this radioactive extravaganza. If you do happen to lose the material, be sure to have access to Tungsten as it is almost the same density (a tad bit higher than U238) and no one is going to notice it until we need to use it in the next war.

mnw21cam 5y ago
Agreed, pop is probably the wrong word. But if the demon core incidents are anything to go by [0], then I can well imaging an unsuspecting worker putting one more block of U238 onto a stack, and feeling a sudden wave of heat and seeing a flash of blue light. And then if they don't have the ability to shove the pile over into a more favourable geometry, seeing the whole pile start to melt into a puddle (which would thankfully also have a more favourable geometry). And then dying of acute radiation syndrome a week later. (Seriously, kids, don't try this at home.) Extreme heat will moderate the reaction to some extent, because the expansion of the metal means it is further apart and therefore has lower reactivity, however the temperature at which it stabilises could well be above the melting point of Uranium. [0] https://en.wikipedia.org/wiki/Demon_core https://en.wikipedia.org/wiki/Demon_core