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User:Praseodymium-141/Protactinium-231

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Protactinium-231, 231Pa
A solution of Protactinium-231
General
Symbol231Pa
NamesProtactinium-231, 231Pa, Pa-231
Protons (Z)91
Neutrons (N)140
Nuclide data
Natural abundance100%
Half-life (t1/2)32600 years[1]
Isotope mass43.9594029[2] Da
Decay products227Ac
Decay modes
Decay modeDecay energy (MeV)
Isotopes of protactinium
Complete table of nuclides

Protactinium-231 is the longest-lived isotope of protactinium, with a half-life of 32,760 years. In nature, it is found in trace amounts as part of the actinium series, which starts with the primordial isotope uranium-235; the equilibrium concentration in uranium ore is 46.55 231Pa per million 235U. In nuclear reactors, it is one of the few long-lived radioactive actinides produced as a byproduct of the projected thorium fuel cycle, as a result of (n,2n) reactions where a fast neutron removes a neutron from 232Th or 232U, and can also be destroyed by neutron capture, though the cross section for this reaction is also low.

binding energy: 1759860 keV
beta decay energy: −382 keV

spin: 3/2−
mode of decay: alpha to 227Ac, also others

possible parent nuclides: beta from 231Th, EC from 231U, alpha from 235Np.

References

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  1. ^ Audi, G.; Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S. (2017). "The NUBASE2016 evaluation of nuclear properties" (PDF). Chinese Physics C. 41 (3): 030001. Bibcode:2017ChPhC..41c0001A. doi:10.1088/1674-1137/41/3/030001.
  2. ^ Wang, M.; Audi, G.; Kondev, F. G.; Huang, W. J.; Naimi, S.; Xu, X. (2017). "The AME2016 atomic mass evaluation (II). Tables, graphs, and references" (PDF). Chinese Physics C. 41 (3): 030003-1–030003-442. doi:10.1088/1674-1137/41/3/030003.
237Np
231U 232U 233U 234U 235U 236U 237U
231Pa 232Pa 233Pa 234Pa
230Th 231Th 232Th 233Th
  • Nuclides with a yellow background in italic have half-lives under 30 days
  • Nuclides in bold have half-lives over 1,000,000 years
  • Nuclides in red frames are fissile