Plutonium-241

Isotope of plutonium

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Plutonium-241, 241PuGeneral

Symbol| 241Pu
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| 241Am
237U
Decay modes
Decay mode| Decay energy (MeV)
β−| 0.02078(17)[1]
α| 5.055(5)[1]
Isotopes of plutonium
Complete table of nuclides

Plutonium-241 (241
Pu or Pu-241) is an isotope of plutonium formed when plutonium-240 captures a neutron. Like some other plutonium isotopes (especially 239Pu), 241Pu is fissile, with a neutron absorption cross section about one-third greater than that of 239Pu, 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 properties

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Process of successive neutron capture from 239Pu through 245Cm, including 241Pu.

Plutonium-241 is a beta emitter with a half-life of 14.3 years, corresponding to a decay of about 5% of 241Pu nuclei over a one-year period. This decay has a Q-value of 20.78±0.17 keV and a mean of 5.227±0.043 keV, and does not emit gamma rays.[1] The longer spent nuclear fuel waits before reprocessing, the more 241Pu decays to americium-241, which is nonfissile (although fissionable by fast neutrons) and an alpha emitter with a half-life of 432 years; 241Am is a major contributor to the radioactivity of nuclear waste on a scale of hundreds or thousands of years.[citation needed] In its fully ionized state, the beta-decay half-life of 241Pu94+ decreases to 4.2 days, and only bound-state beta decay is possible.[2]

Plutonium-241 also has a rare alpha decay branch to uranium-237, occurring in about 0.002% of decays. With a Q-value of 5.055±0.005 MeV, it can emit Auger electrons and associated X-rays, unlike the beta-decay process.[1]

## Role in nuclear fuel

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Americium has lower valence and lower electronegativity than plutonium, neptunium or uranium, so in most nuclear reprocessing, americium tends to fractionate with the alkaline fission products – lanthanides, strontium, caesium, barium, yttrium – rather than with other actinides. Americium is therefore not recycled into nuclear fuel unless special efforts are made.

In a thermal reactor, 241Am captures a neutron to become americium-242, which quickly becomes curium-242 (or, 17.3% of the time, 242Pu) via beta decay. Both 242Cm and 242Pu are much less likely to absorb a neutron, and even less likely to fission; however, 242Cm is short-lived (half-life 160 days) and almost always undergoes alpha decay to 238Pu rather than capturing another neutron. In short, 241Am needs to absorb two neutrons before again becoming a fissile isotope.

Actinides and fission products by half-life

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Actinides[3] by decay chain | Half-life
range (a)  | Fission products of 235U by yield[4]
4n | 4n \+ 1 | 4n \+ 2 | 4n \+ 3 | 4.5–7%  | 0.04–1.25%  | <0.001%
228Ra№ |  |  |  | 4–6 a |  | 155Euþ |
248Bk[5] |  |  |  | > 9 a |  |  |
244Cmƒ | 241Puƒ | 250Cf  | 227Ac№ | 10–29 a | 90Sr  | 85Kr  | 113mCdþ
232Uƒ |  | 238Puƒ | 243Cmƒ | 29–97 a | 137Cs  | 151Smþ | 121mSn
| 249Cfƒ | 242mAmƒ |  | 141–351 a  |

No fission products have a half-life
in the range of 100 a–210 ka ...

| 241Amƒ |  | 251Cfƒ[6] | 430–900 a
|  | 226Ra№ | 247Bk  | 1.3–1.6 ka
240Pu  | 229Th  | 246Cmƒ | 243Amƒ | 4.7–7.4 ka
| 245Cmƒ | 250Cm  |  | 8.3–8.5 ka
|  |  | 239Puƒ | 24.1 ka
|  | 230Th№ | 231Pa№ | 32–76 ka
236Npƒ | 233Uƒ | 234U№ |  | 150–250 ka | 99Tc₡ | 126Sn
248Cm  |  | 242Pu  |  | 327–375 ka |  | 79Se₡
|  |  |  | 1.33 Ma | 135Cs₡
| 237Npƒ |  |  | 1.61–6.5 Ma | 93Zr  | 107Pd
236U  |  |  | 247Cmƒ | 15–24 Ma |  | 129I₡
244Pu  |  |  |  | 80 Ma  |

... nor beyond 15.7 Ma[7]

232Th№ |  | 238U№ | 235Uƒ№ | 0.7–14.1 Ga

* ₡, has thermal neutron capture cross section in the range of 8–50 barns
* ƒ, fissile
* №, primarily a naturally occurring radioactive material (NORM)
* þ, neutron poison (thermal neutron capture cross section greater than 3k barns)

## References

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1. ^ a b c d Basunia, M. S. (1 August 2006). "Nuclear Data Sheets for A = 237". Nuclear Data Sheets. 107 (8): 2323–2422\. doi:10.1016/j.nds.2006.07.001.
2. ^ Takahashi, K.; Boyd, R. N.; Mathews, G. J.; Yokoi, K. (1 October 1987). "Bound-state beta decay of highly ionized atoms". Physical Review C. 36 (4): 1522–1528\. doi:10.1103/PhysRevC.36.1522.
3. ^ 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.
4. ^ Specifically from thermal neutron fission of uranium-235, e.g. in a typical nuclear reactor.
5. ^ 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 Bk248 with a half-life greater than 9 [years]. No growth of Cf248 was detected, and a lower limit for the β− half-life can be set at about 104 [years]. No alpha activity attributable to the new isomer has been detected; the alpha half-life is probably greater than 300 [years]."
6. ^ This is the heaviest nuclide with a half-life of at least four years before the "sea of instability".
7. ^ Excluding those "classically stable" nuclides with half-lives significantly in excess of 232Th; e.g., while 113mCd has a half-life of only fourteen years, that of 113Cd is eight quadrillion years.

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Main isotopes of plutonium

* 238Pu
* 239Pu
* 240Pu
* 241Pu
* 242Pu
* 244Pu

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