uranium-232

Uranium-232 ( ) is an isotope of uranium. It has a half-life of 68.9 years and is a side product in the thorium cycle. It has been cited as an obstacle to nuclear proliferation using 233 U as the fissile material, because the intense gamma radiation emitted by 208 Tl (a daughter of 232 U, produced relatively quickly) makes the 233 U contaminated with it more difficult to handle. Production of 233 U (through the neutron irradiation of 232 Th) invariably produces small amounts of 232 U as an impurity, because of parasitic (n,2n) reactions on uranium-233 itself, or on protactinium-233, or on thorium-232: : 232 Th (n,γ) 233 Th (β − ) 233 Pa (β − ) 233 U (n,2n) 232 U : 232 Th (n,γ) 233 Th (β − ) 233 Pa (n,2n) 232 Pa (β − ) 232 U : 232 Th (n,2n) 231 Th (β − ) 231 Pa (n,γ) 232 Pa (β − ) 232 U Another channel involves neutron capture reaction on small amounts of thorium-230, which is a tiny fraction of natural thorium present due to the decay of uranium-238: : 230 Th (n,γ) 231 Th (β − ) 231 Pa (n,γ) 232 Pa (β − ) 232 U The decay chain of 232 U quickly yields strong gamma radiation emitters: : 232 U (α, 68.9 years) : 228 Th (α, 1.9125 years) (after this, the decay chain is identical to that of 232 Th; thorium-232 is nevertheless much less dangerous because its much longer half-life, 14 billion years or 200 million times that of uranium-232, means the build-up of daughters is that much l…

Uranium-232 ( ) is an isotope of uranium. It has a half-life of 68.9 years and is a side product in the thorium cycle. It has been cited as an obstacle to nuclear proliferation using 233 U as the fissile material, because the intense gamma radiation emitted by 208 Tl (a daughter of 232 U, produced relatively quickly) makes the 233 U contaminated with it more difficult to handle. Production of 233 U (through the neutron irradiation of 232 Th) invariably produces small amounts of 232 U as an impurity, because of parasitic (n,2n) reactions on uranium-233 itself, or on protactinium-233, or on thorium-232: 232 Th (n,γ) 233 Th (β − ) 233 Pa (β − ) 233 U (n,2n) 232 U 232 Th (n,γ) 233 Th (β − ) 233 Pa (n,2n) 232 Pa (β − ) 232 U 232 Th (n,2n) 231 Th (β − ) 231 Pa (n,γ) 232 Pa (β − ) 232 U Another channel involves neutron capture reaction on small amounts of thorium-230, which is a tiny fraction of natural thorium present due to the decay of uranium-238: 230 Th (n,γ) 231 Th (β − ) 231 Pa (n,γ) 232 Pa (β − ) 232 U The decay chain of 232 U quickly yields strong gamma radiation emitters: 232 U (α, 68.9 years) 228 Th (α, 1.9125 years) (after this, the decay chain is identical to that of 232 Th; thorium-232 is nevertheless much less dangerous because its much longer half-life, 14 billion years or 200 million times that of uranium-232, means the build-up of daughters is that much less for equal mass) 224 Ra (α, 3.632 days) 220 Rn (α, 55.6 s) 216 Po (α, 0.144 s) 212 Pb (β − , 10.627 h) 212 Bi (α, 60.55 min, 0.78 MeV), with 35.94% branching ratio to 208 Tl (β − , 3.053 min), 99.75% chance to emit 2.6 MeV gamma ray 208 Pb (stable) This makes manual handling in a glove box with only light shielding (as commonly done with plutonium) too hazardous, except in a period short compared to the Th-228 half-life just after chemical separation of the uranium, and instead requiring remote manipulation for fuel fabrication. Unusually for an isotope with even mass number, 232 U has a significant neutron absorption cross section for fission (thermal neutrons , resonance integral ) as well as for neutron capture (thermal , resonance integral ). This makes it a fissile isotope, though using it alone in a reactor or bomb is not reasonable.

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