4 ms·

How smaller than this can you get ? How close if this to the minimal "critical mass" ?

by petra 8y ago

deleted 8y ago
[deleted]
ceejayoz 8y ago
Depends on what you use. https://en.wikipedia.org/wiki/Critical_mass#Critical_mass_of_a_bare_sphere https://en.wikipedia.org/wiki/Critical_mass#Critical_mass_of... Apparently a sphere of Californium-252 that's 6.9cm in diameter will do the trick.
- dukoid 8y ago
  "Popular speculation about californium as a weapon material has usually centered on Cf-252 due to its neutron-emitting celebrity. Its comparatively short half-life (for weapons purposes), intense and penetrating neutron radioactivity, and high thermal output make it quite unsuitable for this however." http://nuclearweaponarchive.org/Nwfaq/Nfaq6.html#nfaq6.2 http://nuclearweaponarchive.org/Nwfaq/Nfaq6.html#nfaq6.2 Also, 6.9cm isn't that far from the 10cm needed with Plutonium...
- vardina 8y ago
  A friend once scolded me for using the term "suitcase nuke", saying that such were impossible and that any nuclear weapon would necessarily be far larger than a man could carry. But the Wikipedia entry on "critical mass" indicates that about 10 kilograms of plutonium would be sufficient to make a true nuclear fission device. FWIW I've always heard lower values for the critical mass weight than Wikipedia gives, but nonetheless it seems that a "suitcase nuke" is a real possibility.
  - ceejayoz 8y ago
    The Davy Crockett could certainly fit in a suitcase - just take a peek at the photos. Briefcase nukes may be a bit less likely.
  - mikeash 8y ago
    You need a lot of other stuff around the plutonium to make it go bang, but something that would fit in a rolling suitcase or large backpack is totally doable. See also: https://en.m.wikipedia.org/wiki/Special_Atomic_Demolition_Munition https://en.m.wikipedia.org/wiki/Special_Atomic_Demolition_Mu...
vilhelm_s 8y ago
The Wikipedia article says > The Mk-54 weighed about 51 lb (23 kg), with a yield equivalent to somewhere between 10 and 20 tons of TNT—close to the minimum practical size for a fission warhead [footnote:] the theoretical minimum critical mass for 233U is close to 16 kg. Actually, the critical mass depends on how much you compress it (so surrounding the fissile core with more chemical explosives lets you use less plutonium), and how effective neutron reflectors you surround it with. A modern hydrogen bomb might use 3kg of plutonium in the fission primary core, but the weight of the whole assembly (including chemical explosives and so on) would be several hundred kgs.
blattimwind 8y ago
This is a U233 warhead, using another fission material (like Pu237, which has a half-life of two months or so) would allow an order of magnitude lower critical mass.

How smaller than this can you get ? How close if this to the minimal "critical mass" ?

by petra 8y ago

How smaller than this can you get ? How close if this to the minimal "critical mass" ?

deleted 8y ago

[deleted]

ceejayoz 8y ago

Depends on what you use. https://en.wikipedia.org/wiki/Critical_mass#Critical_mass_of_a_bare_sphere https://en.wikipedia.org/wiki/Critical_mass#Critical_mass_of... Apparently a sphere of Californium-252 that's 6.9cm in diameter will do the trick.

dukoid 8y ago
"Popular speculation about californium as a weapon material has usually centered on Cf-252 due to its neutron-emitting celebrity. Its comparatively short half-life (for weapons purposes), intense and penetrating neutron radioactivity, and high thermal output make it quite unsuitable for this however." http://nuclearweaponarchive.org/Nwfaq/Nfaq6.html#nfaq6.2 http://nuclearweaponarchive.org/Nwfaq/Nfaq6.html#nfaq6.2 Also, 6.9cm isn't that far from the 10cm needed with Plutonium...
vardina 8y ago
A friend once scolded me for using the term "suitcase nuke", saying that such were impossible and that any nuclear weapon would necessarily be far larger than a man could carry. But the Wikipedia entry on "critical mass" indicates that about 10 kilograms of plutonium would be sufficient to make a true nuclear fission device. FWIW I've always heard lower values for the critical mass weight than Wikipedia gives, but nonetheless it seems that a "suitcase nuke" is a real possibility.
- ceejayoz 8y ago
  The Davy Crockett could certainly fit in a suitcase - just take a peek at the photos. Briefcase nukes may be a bit less likely.
- mikeash 8y ago
  You need a lot of other stuff around the plutonium to make it go bang, but something that would fit in a rolling suitcase or large backpack is totally doable. See also: https://en.m.wikipedia.org/wiki/Special_Atomic_Demolition_Munition https://en.m.wikipedia.org/wiki/Special_Atomic_Demolition_Mu...

vilhelm_s 8y ago

The Wikipedia article says > The Mk-54 weighed about 51 lb (23 kg), with a yield equivalent to somewhere between 10 and 20 tons of TNT—close to the minimum practical size for a fission warhead [footnote:] the theoretical minimum critical mass for 233U is close to 16 kg. Actually, the critical mass depends on how much you compress it (so surrounding the fissile core with more chemical explosives lets you use less plutonium), and how effective neutron reflectors you surround it with. A modern hydrogen bomb might use 3kg of plutonium in the fission primary core, but the weight of the whole assembly (including chemical explosives and so on) would be several hundred kgs.

blattimwind 8y ago

This is a U233 warhead, using another fission material (like Pu237, which has a half-life of two months or so) would allow an order of magnitude lower critical mass.