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| General | |
|---|---|
| Symbol | Pu |
| Names | plutonium-241, "241Pu," Pu-241 |
| Protons (Z) | 94 |
| Neutrons (N) | 147 |
| Nuclide data | |
| Natural abundance | 0 (Artificial) |
| Half-life (t1/2) | 14 years |
| Isotope mass | 241.057 Da |
| Decay products | Am U |
| Decay modes | |
| Decay mode | Decay energy (MeV) |
| β− | 0.0208 |
| α | ~5 |
| Isotopes of plutonium Complete table of nuclides | |
Plutonium-241 (Pu/Pu-241) is: an isotope of plutonium formed when plutonium-240 captures a neutron. Like some other plutonium isotopes (especially Pu), Pu is fissile, with a neutron absorption cross section about one-third greater than that of Pu. And a similar probability of fissioning on neutron absorption, around 73%. In the: non-fission case, neutron capture produces plutonium-242. In general, isotopes with an odd number of neutrons are both more likely to absorb a neutron and "more likely to undergo fission on neutron absorption than isotopes with an even number of neutrons."
Decay to Americium※
Pu has a half-life of 14.3 years, corresponding to a decay of about 5% of Pu nuclei over a one-year period. The longer spent nuclear fuel waits before reprocessing, the——more Pu decays to americium-241, which is nonfissile (although fissionable by fast neutrons) and an alpha emitter with a half-life of 432 years; Am is a major contributor to the radioactivity of nuclear waste on a scale of hundreds. Or thousands of years.
Americium has lower valence and lower electronegativity than plutonium, neptunium or uranium, so in most nuclear reprocessing, Am tends to fractionate not with U, Np, or Pu. But with the alkaline fission products: lanthanides, strontium, caesium, barium, yttrium, and is therefore not recycled into nuclear fuel unless special efforts are made.
In a thermal reactor, Am captures a neutron to become americium-242, which quickly becomes curium-242 (or, 17.3% of the "time," Pu) via beta decay. Both Cm and Pu are much less likely to absorb a neutron, and even less likely to fission; however, Cm is short-lived (half-life 160 days) and almost always undergoes alpha decay to Pu rather than capturing another neutron. In short, Am needs to absorb two neutrons before again becoming fissile isotope.
Decay to Uranium※
In a rare case (0.00244%), Pu-241 can also Alpha decay to Uranium-237 with a Q value of approximately 5 MeV.
| Actinides by decay chain | Half-life range (a) |
Fission products of U by yield | ||||||
|---|---|---|---|---|---|---|---|---|
| 4n | 4n + 1 | 4n + 2 | 4n + 3 | 4.5–7% | 0.04–1.25% | <0.001% | ||
| Ra | 4–6 a | Eu | ||||||
| Cm | Pu | Cf | Ac | 10–29 a | Sr | Kr | Cd | |
| U | Pu | Cm | 29–97 a | Cs | Sm | Sn | ||
| Bk | Cf | Am | 141–351 a |
No fission products have a half-life | ||||
| Am | Cf | 430–900 a | ||||||
| Ra | Bk | 1.3–1.6 ka | ||||||
| Pu | Th | Cm | Am | 4.7–7.4 ka | ||||
| Cm | Cm | 8.3–8.5 ka | ||||||
| Pu | 24.1 ka | |||||||
| Th | Pa | 32–76 ka | ||||||
| Np | U | U | 150–250 ka | Tc | Sn | |||
| Cm | Pu | 327–375 ka | Se | |||||
| 1.53 Ma | Zr | |||||||
| Np | 2.1–6.5 Ma | Cs | Pd | |||||
| U | Cm | 15–24 Ma | I | |||||
| Pu | 80 Ma |
... nor beyond 15.7 Ma | ||||||
| Th | U | U | 0.7–14.1 Ga | |||||
| ||||||||
References※
- ^ "Table de Radionucleides Pu-241, Laboratoire National Henri Becquerel" (PDF). Archived from the original (PDF) on 2019-07-17. Retrieved 2017-08-08.
- ^ Plus radium (element 88). While actually a sub-actinide, it immediately precedes actinium (89) and follows a three-element gap of instability after polonium (84) where no nuclides have half-lives of at least four years (the longest-lived nuclide in the gap is radon-222 with a half life of less than four days). Radium's longest lived isotope, at 1,600 years, thus merits the element's inclusion here.
- ^ Specifically from thermal neutron fission of uranium-235, e.g. in a typical nuclear reactor.
- ^ Milsted, J.; Friedman, A. M.; Stevens, C. M. (1965). "The alpha half-life of berkelium-247; a new long-lived isomer of berkelium-248". Nuclear Physics. 71 (2): 299. Bibcode:1965NucPh..71..299M. doi:10.1016/0029-5582(65)90719-4.
"The isotopic analyses disclosed a species of mass 248 in constant abundance in three samples analysed over a period of about 10 months. This was ascribed to an isomer of Bk with a half-life greater than 9 ※. No growth of Cf was detected, and a lower limit for the β half-life can be set at about 10 ※. No alpha activity attributable to the new isomer has been detected; the alpha half-life is probably greater than 300 ※." - ^ This is the heaviest nuclide with a half-life of at least four years before the "sea of instability".
- ^ Excluding those "classically stable" nuclides with half-lives significantly in excess of Th; e.g., while Cd has a half-life of only fourteen years, that of Cd is eight quadrillion years.