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Nuclear weapons: Difference between revisions

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* Fission chain reactions release thermal (slow) neutrons. Thermal neutrons affect materials differently:
* Fission chain reactions release thermal (slow) neutrons. Thermal neutrons affect materials differently:
** <sup>233</sup>U is fissile, and can be bred from <sup>232</sup>Th. Without subsequent physical enrichment, however, it'll be contaminated to some degree by:
** <sup>233</sup>U is fissile, and can be bred from <sup>232</sup>Th. Without subsequent physical enrichment, however, it'll be contaminated to some degree by:
*** <sup>232</sup>U ((<sup>233</sup>U,'n') -> <sup>232</sup>U + '2n', (<sup>232</sup>Pa,β−) -> <sup>232</sup>U), a retarded younger brother notable for meager lifespan and γ-rich decay chain (though note that Georgia Tech researchers have fashioned <sup>232</sup>UBe<sub>13</sub> (<sup>232</sup>uranium beryllide) [http://smartech.gatech.edu/handle/1853/14650 neutron initiators], so it has that).
*** <sup>232</sup>U ((<sup>233</sup>U,''n'') -> <sup>232</sup>U + ''2n'', (<sup>232</sup>Pa,β−) -> <sup>232</sup>U), a retarded younger brother notable for meager lifespan and γ-rich decay chain (though note that Georgia Tech researchers have fashioned <sup>232</sup>UBe<sub>13</sub> (<sup>232</sup>uranium beryllide) [http://smartech.gatech.edu/handle/1853/14650 neutron initiators], so it has that).
** <sup>235</sup>U is fissile, but requires enrichment infrastructure (no plausible breeding path). Given sufficient mass of highly-enriched uranium, it's a real dream to work with, and criticality is about as difficult as lighting a Sparkler. With a 700+ million year half-life, it's not going anywhere, either. Modern cores employ <sup>239</sup>Pu for three reasons: (a) smaller critical mass (b) beancounting and (c) style.
** <sup>235</sup>U is fissile, but requires enrichment infrastructure (no plausible breeding path). Given sufficient mass of highly-enriched uranium, it's a real dream to work with, and criticality is about as difficult as lighting a Sparkler. With a 700+ million year half-life, it's not going anywhere, either. Modern cores employ <sup>239</sup>Pu for three reasons: (a) smaller critical mass (b) beancounting and (c) style.
** <sup>238</sup>U is not fissile, but can be bred into <sup>239</sup>Pu. Furthermore, it 'can' be fissioned by the 14.7 MeV neutron resulting from D-T fusion, and there's an absolute ton of it.
** <sup>238</sup>U is not fissile, but can be bred into <sup>239</sup>Pu. Furthermore, it ''can'' be fissioned by the 14.7 MeV neutron resulting from D-T fusion, and there's an absolute ton of it.
** <sup>239</sup>Pu is fissile, and can be chemically extracted from activated actinides (primarily <sup>238</sup>U breeding). Without subsequent physical enrichment, however, it'll be contaminated to some degree by:
** <sup>239</sup>Pu is fissile, and can be chemically extracted from activated actinides (primarily <sup>238</sup>U breeding). Without subsequent physical enrichment, however, it'll be contaminated to some degree by:
*** <sup>240</sup>Pu becomes a <sup>241</sup>Pu rather than compound {<sup>241</sup>Pu} (fission precursor), meaning two neutrons (and associated time) to yield a fission event. Predetonation hazard due to spontaneous fissions. Burnable in a recycling reactor, but undesirable for weapon material.
*** <sup>240</sup>Pu becomes a <sup>241</sup>Pu rather than compound {<sup>241</sup>Pu} (fission precursor), meaning two neutrons (and associated time) to yield a fission event. Predetonation hazard due to spontaneous fissions. Burnable in a recycling reactor, but undesirable for weapon material.