View source for Physics:Isotopes of plutonium

{{Short description|Artificial nuclides with atomic number of 94 but with different mass numbers}}
{{Infobox plutonium isotopes}}
[[Chemistry:Plutonium|Plutonium]] (<sub>94</sub>Pu) is an artificial element, except for trace quantities resulting from [[Physics:Neutron capture|neutron capture]] by uranium, and thus a [[Physics:Standard atomic weight|standard atomic weight]] cannot be given. Like all artificial elements, it has no [[Physics:Stable isotope|stable isotope]]s. It was synthesized long before being found in nature, the first [[Physics:Isotope|isotope]] synthesized being <sup>238</sup>Pu in 1940. Twenty plutonium radioisotopes have been characterized. The most stable are [[Physics:Plutonium-244|plutonium-244]] with a [[Physics:Half-life|half-life]] of 80.8 million years, [[Physics:Plutonium-242|plutonium-242]] with a half-life of 373,300 years, and [[Physics:Plutonium-239|plutonium-239]] with a half-life of 24,110 years. All of the remaining [[Physics:Radioactive|radioactive]] isotopes have half-lives that are less than 7,000 years. This element also has eight meta states; all have half-lives of less than one second.

The '''isotopes of plutonium''' range in [[Physics:Atomic weight|atomic weight]] from 228.0387&nbsp;u (<sup>228</sup>Pu) to 247.074&nbsp;u (<sup>247</sup>Pu). The primary decay modes before the most stable isotope, <sup>244</sup>Pu, are [[Physics:Spontaneous fission|spontaneous fission]] and alpha emission; the primary mode after is [[Physics:Beta emission|beta emission]]. The primary [[Physics:Decay product|decay product]]s before <sup>244</sup>Pu are [[Physics:Isotopes of uranium|isotopes of uranium]] and [[Physics:Isotopes of neptunium|neptunium]] (not considering fission products), and the primary decay products after are [[Physics:Isotopes of americium|isotopes of americium]].

== List of isotopes ==
{{Isotopes table
|symbol=Pu
|refs=<!-- not NUBASE2016 yet (2019-07-14) -->
|notes=m, unc(), mass#, spin(), spin#, daughter-st, daughter-nst, EC, SF, CD, IT
}}
|-
| rowspan=2|<sup>228</sup>Pu
| rowspan=2 style="text-align:right" | 94
| rowspan=2 style="text-align:right" | 134
| rowspan=2|228.03874(3)
| rowspan=2|{{val|1.1|20|5|u=s}}
| α 
| <sup>224</sup>U
| rowspan=2|0+
| rowspan=2|
|-
| [[Physics:Beta decay|β<sup>+</sup>]] (rare)
| <sup>228</sup>Np
|-
| rowspan=2|<sup>229</sup>Pu<ref>{{cite journal |last1=Kondev |first1=F. G. |last2=Wang |first2=M. |last3=Huang |first3=W. J. |last4=Naimi |first4=S. |last5=Audi |first5=G. |title=The NUBASE2020 evaluation of nuclear physics properties * |journal=Chinese Physics C, High Energy Physics and Nuclear Physics |date=1 March 2021 |volume=45 |issue=3 |page=030001 |doi=10.1088/1674-1137/abddae |bibcode=2021ChPhC..45c0001K |osti=1774641 |s2cid=233794940 |language=English |issn=1674-1137|doi-access=free }}</ref>
| rowspan=2 style="text-align:right" | 94
| rowspan=2 style="text-align:right" | 135
| rowspan=2|229.04015(6)
| rowspan=2|91(26)&nbsp;s
| α (50%)
| <sup>225</sup>U
| rowspan=2|3/2+#
| rowspan=2|
|-
| β<sup>+</sup> (50%)
| <sup>229</sup>Np
|-
| rowspan=2|<sup>230</sup>Pu
| rowspan=2 style="text-align:right" | 94
| rowspan=2 style="text-align:right" | 136
| rowspan=2|230.039650(16)
| rowspan=2|1.70(17)&nbsp;min
| α (>73%)<ref>{{cite journal |last1=Wilson |first1=G. L. |last2=Takeyama |first2=M. |last3=Andreyev |first3=A. N. |last4=Andel |first4=B. |last5=Antalic |first5=S. |last6=Catford |first6=W. N. |last7=Ghys |first7=L. |last8=Haba |first8=H. |last9=Heßberger |first9=F. P. |last10=Huang |first10=M. |last11=Kaji |first11=D. |last12=Kalaninova |first12=Z. |last13=Morimoto |first13=K. |last14=Morita |first14=K. |last15=Murakami |first15=M. |last16=Nishio |first16=K. |last17=Orlandi |first17=R. |last18=Smith |first18=A. G. |last19=Tanaka |first19=K. |last20=Wakabayashi |first20=Y. |last21=Yamaki |first21=S. |title=β -delayed fission of Am 230 |journal=Physical Review C |date=13 October 2017 |volume=96 |issue=4 |page=044315 |doi=10.1103/PhysRevC.96.044315 |language=en |issn=2469-9985|doi-access=free }}</ref>
| <sup>226</sup>U
| rowspan=2|0+
| rowspan=2|
|-
| β<sup>+</sup> (<27%)
| <sup>230</sup>Np
|-
| rowspan=2|<sup>231</sup>Pu<ref>{{cite journal |last1=Kondev |first1=F. G. |last2=Wang |first2=M. |last3=Huang |first3=W. J. |last4=Naimi |first4=S. |last5=Audi |first5=G. |title=The NUBASE2020 evaluation of nuclear physics properties * |journal=Chinese Physics C, High Energy Physics and Nuclear Physics |date=1 March 2021 |volume=45 |issue=3 |page=030001 |doi=10.1088/1674-1137/abddae |bibcode=2021ChPhC..45c0001K |osti=1774641 |s2cid=233794940 |language=English |issn=1674-1137|doi-access=free }}</ref>
| rowspan=2 style="text-align:right" | 94
| rowspan=2 style="text-align:right" | 137
| rowspan=2|231.041101(28)
| rowspan=2|8.6(5)&nbsp;min
| β<sup>+</sup> (87%)
| <sup>231</sup>Np
| rowspan=2|(3/2+)
| rowspan=2|
|-
| α (13%)
| <sup>227</sup>U
|-
| rowspan=2|<sup>232</sup>Pu
| rowspan=2 style="text-align:right" | 94
| rowspan=2 style="text-align:right" | 138
| rowspan=2|232.041187(19)
| rowspan=2|33.7(5)&nbsp;min
| [[Physics:Electron capture|EC]] (89%)
| <sup>232</sup>Np
| rowspan=2|0+
| rowspan=2|
|-
| α (11%)
| <sup>228</sup>U
|-
| rowspan=2|<sup>233</sup>Pu
| rowspan=2 style="text-align:right" | 94
| rowspan=2 style="text-align:right" | 139
| rowspan=2|233.04300(5)
| rowspan=2|20.9(4)&nbsp;min
| β<sup>+</sup> (99.88%)
| <sup>233</sup>Np
| rowspan=2|5/2+#
| rowspan=2|
|-
| α (.12%)
| <sup>229</sup>U
|-
| rowspan=2|<sup>234</sup>Pu
| rowspan=2 style="text-align:right" | 94
| rowspan=2 style="text-align:right" | 140
| rowspan=2|234.043317(7)
| rowspan=2|8.8(1)&nbsp;h
| EC (94%)
| <sup>234</sup>Np
| rowspan=2|0+
| rowspan=2|
|-
| α (6%)
| <sup>230</sup>U
|-
| rowspan=2|<sup>235</sup>Pu
| rowspan=2 style="text-align:right" | 94
| rowspan=2 style="text-align:right" | 141
| rowspan=2|235.045286(22)
| rowspan=2|25.3(5)&nbsp;min
| β<sup>+</sup> (99.99%)
| <sup>235</sup>Np
| rowspan=2|(5/2+)
| rowspan=2|
|-
| α (.0027%)
| <sup>231</sup>U
|-
| rowspan=3|<sup>236</sup>Pu
| rowspan=3 style="text-align:right" | 94
| rowspan=3 style="text-align:right" | 142
| rowspan=3|236.0460580(24)
| rowspan=3|2.858(8)&nbsp;y
| α
| <sup>232</sup>U
| rowspan=3|0+
| rowspan=3|
|-
| [[Physics:Spontaneous fission|SF]] (1.37×10<sup>−7</sup>%)
| (various)
|-
| [[Physics:Cluster decay|CD]] (2×10<sup>−12</sup>%)
| '''<sup>208</sup>Pb'''<br/><sup>28</sup>Mg
|-
| rowspan=2|<sup>237</sup>Pu
| rowspan=2 style="text-align:right" | 94
| rowspan=2 style="text-align:right" | 143
| rowspan=2|237.0484097(24)
| rowspan=2|45.2(1)&nbsp;d
| EC
| <sup>237</sup>Np
| rowspan=2|7/2−
| rowspan=2|
|-
| α (.0042%)
| <sup>233</sup>U
|-
| style="text-indent:1em" | <sup>237m1</sup>Pu
| colspan="3" style="text-indent:2em" | 145.544(10)2&nbsp;keV
| 180(20)&nbsp;ms
| IT
| <sup>237</sup>Pu
| 1/2+
|
|-
| style="text-indent:1em" | <sup>237m2</sup>Pu
| colspan="3" style="text-indent:2em" | 2900(250)&nbsp;keV
| 1.1(1)&nbsp;μs
|
|
|
|
|-
| rowspan=4|[[Physics:Plutonium-238|<sup>238</sup>Pu]]
| rowspan=4 style="text-align:right" | 94
| rowspan=4 style="text-align:right" | 144
| rowspan=4|238.0495599(20)
| rowspan=4|87.7(1)&nbsp;y
| α
| <sup>234</sup>U
| rowspan=4|0+
| rowspan=4|Trace<ref group=n>[[Physics:Double beta decay|Double beta decay]] product of [[Physics:Uranium-238|<sup>238</sup>U]]</ref>
|-
| SF (1.9×10<sup>−7</sup>%)
| (various)
|-
| CD (1.4×10<sup>−14</sup>%)
| <sup>206</sup>Hg<br><sup>32</sup>Si
|-
| CD (6×10<sup>−15</sup>%)
| <sup>180</sup>Yb<br><sup>30</sup>Mg<br><sup>28</sup>Mg
|-
| rowspan=2|[[Physics:Plutonium-239|<sup>239</sup>Pu]]<ref group="n" name="f">fissile nuclide</ref><ref group="n">Most useful isotope for nuclear weapons</ref>
| rowspan=2 style="text-align:right" | 94
| rowspan=2 style="text-align:right" | 145
| rowspan=2|239.0521634(20)
| rowspan=2|2.411(3)×10<sup>4</sup>&nbsp;y
| α
| '''''<sup>235</sup>U'''''
| rowspan=2|1/2+
| rowspan=2|Trace<ref group=n>[[Physics:Neutron capture|Neutron capture]] product of [[Physics:Uranium-238|<sup>238</sup>U]]</ref>
|-
| SF (3.1×10<sup>−10</sup>%)
| (various)
|-
| style="text-indent:1em" | <sup>239m1</sup>Pu
| colspan="3" style="text-indent:2em" | 391.584(3)&nbsp;keV
| 193(4)&nbsp;ns
|
|
| 7/2−
|
|-
| style="text-indent:1em" | <sup>239m2</sup>Pu
| colspan="3" style="text-indent:2em" | 3100(200)&nbsp;keV
| 7.5(10)&nbsp;μs
|
|
| (5/2+)
|
|-
| rowspan=3|[[Physics:Plutonium-240|<sup>240</sup>Pu]]
| rowspan=3 style="text-align:right" | 94
| rowspan=3 style="text-align:right" | 146
| rowspan=3|240.0538135(20)
| rowspan=3|6.561(7)×10<sup>3</sup> y
| α
| <sup>236</sup>U
| rowspan=3|0+
| rowspan=3|Trace<ref group=n>Intermediate decay product of [[Physics:Plutonium-244|<sup>244</sup>Pu]]</ref>
|-
| SF (5.7×10<sup>−6</sup>%)
| (various)
|-
| CD (1.3×10<sup>−13</sup>%)
| <sup>206</sup>Hg<br><sup>34</sup>Si
|-
| rowspan=3|[[Physics:Plutonium-241|<sup>241</sup>Pu]]<ref group="n" name="f" />
| rowspan=3 style="text-align:right" | 94
| rowspan=3 style="text-align:right" | 147
| rowspan=3|241.0568515(20)
| rowspan=3|14.290(6)&nbsp;y
| β<sup>−</sup> (99.99%)
| <sup>241</sup>Am
| rowspan=3|5/2+
| rowspan=3|
|-
| α (.00245%)
| <sup>237</sup>U
|-
| SF (2.4×10<sup>−14</sup>%)
| (various)
|-
| style="text-indent:1em" | <sup>241m1</sup>Pu
| colspan="3" style="text-indent:2em" | 161.6(1)&nbsp;keV
| 0.88(5)&nbsp;μs
|
|
| 1/2+
|
|-
| style="text-indent:1em" | <sup>241m2</sup>Pu
| colspan="3" style="text-indent:2em" | 2200(200)&nbsp;keV
| 21(3)&nbsp;μs
|
|
|
|
|-
| rowspan=2|[[Physics:Plutonium-242|<sup>242</sup>Pu]]
| rowspan=2 style="text-align:right" | 94
| rowspan=2 style="text-align:right" | 148
| rowspan=2|242.0587426(20)
| rowspan=2|3.75(2)×10<sup>5</sup>&nbsp;y
| α
| '''''<sup>238</sup>U'''''
| rowspan=2|0+
| rowspan=2|
|-
| SF (5.5×10<sup>−4</sup>%)
| (various)
|-
| <sup>243</sup>Pu<ref group="n" name="f" />
| style="text-align:right" | 94
| style="text-align:right" | 149
| 243.062003(3)
| 4.956(3)&nbsp;h
| β<sup>−</sup>
| <sup>243</sup>Am
| 7/2+
|
|-
| style="text-indent:1em" | <sup>243m</sup>Pu
| colspan="3" style="text-indent:2em" | 383.6(4)&nbsp;keV
| 330(30)&nbsp;ns
|
|
| (1/2+)
|
|-
| rowspan=3|[[Physics:Plutonium-244|<sup>244</sup>Pu]]
| rowspan=3 style="text-align:right" | 94
| rowspan=3 style="text-align:right" | 150
| rowspan=3|244.064204(5)
| rowspan=3|8.00(9)×10<sup>7</sup>&nbsp;y
| α (99.88%)
| <sup>240</sup>U
| rowspan=3|0+
| rowspan=3|Trace<ref group=n>Interstellar, some may also be [[Chemistry:Primordial nuclide|primordial]] but such claims are disputed</ref>
|-
| SF (.123%)
| (various)
|-
| [[Physics:Double beta decay|β<sup>−</sup>β<sup>−</sup>]] (<7.3×10<sup>−9</sup>%)
| <sup>244</sup>Cm
|-
| <sup>245</sup>Pu
| style="text-align:right" | 94
| style="text-align:right" | 151
| 245.067747(15)
| 10.5(1)&nbsp;h
| β<sup>−</sup>
| <sup>245</sup>Am
| (9/2−)
|
|-
| <sup>246</sup>Pu
| style="text-align:right" | 94
| style="text-align:right" | 152
| 246.070205(16)
| 10.84(2)&nbsp;d
| β<sup>−</sup>
| <sup>246m</sup>Am
| 0+
|
|-
| <sup>247</sup>Pu
| style="text-align:right" | 94
| style="text-align:right" | 153
| 247.07407(32)#
| 2.27(23)&nbsp;d
| β<sup>−</sup>
| <sup>247</sup>Am
| 1/2+#
|
{{Isotopes table/footer}}

==Actinides vs fission products==
{{Actinidesvsfissionproducts}}
{{Clear}}

== Notable isotopes ==
*[[Physics:Plutonium-238|Plutonium-238]] has a half-life of 87.74 years<ref>{{cite magazine|last1=Makhijani|first1=Arjun|last2=Seth|first2=Anita|date=July 1997|title=The Use of Weapons Plutonium as Reactor Fuel|url=http://ieer.org/wp/wp-content/uploads/1997/07/no-3.pdf|magazine=Energy and Security|location=Takoma Park, MD|publisher=Institute for Energy and Environmental Research|access-date=4 July 2016}}</ref> and emits [[Physics:Alpha particle|alpha particle]]s. Pure <sup>238</sup>Pu for [[Physics:Radioisotope thermoelectric generator|radioisotope thermoelectric generator]]s that power some [[Engineering:Spacecraft|spacecraft]] is produced by neutron capture on [[Physics:Neptunium-237|neptunium-237]] but plutonium from [[Physics:Spent nuclear fuel|spent nuclear fuel]] can contain as much as a few percent <sup>238</sup>Pu, originating from <sup>237</sup>Np, [[Physics:Alpha decay|alpha decay]] of <sup>242</sup>Cm, or (n,2n) reactions.
*[[Physics:Plutonium-239|Plutonium-239]] is the most important isotope of plutonium{{Citation needed|date=July 2015}}, with a half-life of 24,100&nbsp;years. <sup>239</sup>Pu and <sup>241</sup>Pu are fissile, meaning that the nuclei of their atoms can [[Physics:Nuclear fission|break apart]] by being bombarded by [[Physics:Neutron temperature|slow moving]] thermal neutrons, releasing energy, gamma radiation and [[Physics:Neutron radiation|more neutrons]]. It can therefore sustain a [[Physics:Nuclear chain reaction|nuclear chain reaction]], leading to applications in [[Engineering:Nuclear weapon|nuclear weapon]]s and [[Physics:Nuclear reactor|nuclear reactor]]s. <sup>239</sup>Pu is synthesized by irradiating [[Physics:Uranium-238|uranium-238]] with neutrons in a nuclear reactor, then recovered via [[Physics:Nuclear reprocessing|nuclear reprocessing]] of the fuel. Further [[Physics:Neutron capture|neutron capture]] produces successively heavier isotopes.
*[[Physics:Plutonium-240|Plutonium-240]] has a high rate of spontaneous fission, raising the background [[Physics:Neutron radiation|neutron radiation]] of plutonium containing it. Plutonium is graded by proportion of <sup>240</sup>Pu: weapons grade (<&nbsp;7%), fuel grade (7–19%) and reactor grade (>&nbsp;19%). Lower grades are less suited for nuclear weapons and thermal reactors but can fuel [[Physics:Fast reactor|fast reactor]]s.
*[[Physics:Plutonium-241|Plutonium-241]] is fissile, but also [[Physics:Beta decay|beta decay]]s with a half-life of 14 years to [[Physics:Americium-241|americium-241]].
*[[Physics:Plutonium-242|Plutonium-242]] is not fissile, not very fertile (requiring 3 more neutron captures to become fissile), has a low neutron capture cross section, and a longer half-life than any of the lighter isotopes.
*[[Physics:Plutonium-244|Plutonium-244]] is the most stable isotope of plutonium, with a half-life of about 80&nbsp;million years. It is not significantly produced in nuclear reactors because <sup>243</sup>Pu has a short half-life, but some is produced in nuclear explosions. Plutonium-244 has been found in interstellar space<ref name="WallnerFaestermann2015">{{cite journal|last1=Wallner|first1=A.|last2=Faestermann|first2=T.|last3=Feige|first3=J.|last4=Feldstein|first4=C.|last5=Knie|first5=K.|last6=Korschinek|first6=G.|last7=Kutschera|first7=W.|last8=Ofan|first8=A.|last9=Paul|first9=M.|last10=Quinto|first10=F.|last11=Rugel|first11=G.|last12=Steier|first12=P.|title=Abundance of live 244Pu in deep-sea reservoirs on Earth points to rarity of actinide nucleosynthesis|journal=Nature Communications|volume=6|year=2015|pages=5956|issn=2041-1723|doi=10.1038/ncomms6956|pmid=25601158|pmc=4309418|arxiv=1509.08054|bibcode=2015NatCo...6.5956W}}</ref> and has the second longest half-life of any non-primordial radioisotope.

==Production and uses==
[[File:Plutonium pellet.jpg|right|thumb|250px|A pellet of [[Physics:Plutonium-238|plutonium-238]], glowing from its own heat, used for radioisotope thermoelectric generators.]]
[[File:Sasahara.svg|thumb|375px|[[Physics:Nuclear transmutation|Transmutation]] flow between <sup>238</sup>Pu and <sup>244</sup>Cm in LWR.<ref>{{cite journal|title=Neutron and Gamma Ray Source Evaluation of LWR High Burn-up UO2 and MOX Spent Fuels |journal=Journal of Nuclear Science and Technology |volume=41 |issue=4 |pages=448–456 |date=April 2004 |doi=10.3327/jnst.41.448 |last1=Sasahara |first1=Akihiro |last2=Matsumura |first2=Tetsuo |last3=Nicolaou |first3=Giorgos |last4=Papaioannou |first4=Dimitri |doi-access=free }}</ref><br/>Transmutation speed not shown and varies greatly by nuclide.<br/><sup>245</sup>Cm&ndash;<sup>248</sup>Cm are long-lived with negligible decay.]]
<sup>239</sup>Pu, a fissile isotope that is the second most used [[Physics:Nuclear fuel|nuclear fuel]] in nuclear reactors after [[Physics:Uranium-235|uranium-235]], and the most used fuel in the [[Physics:Nuclear fission|fission]] portion of [[Engineering:Nuclear weapon|nuclear weapon]]s, is produced from [[Physics:Uranium-238|uranium-238]] by neutron capture followed by two beta decays.

<sup>240</sup>Pu, <sup>241</sup>Pu, and <sup>242</sup>Pu are produced by further neutron capture. The odd-mass isotopes <sup>239</sup>Pu and <sup>241</sup>Pu have about a 3/4 chance of undergoing [[Physics:Nuclear fission|fission]] on capture of a thermal neutron and about a 1/4 chance of retaining the [[Physics:Neutron|neutron]] and becoming the next heavier isotope. The even-mass isotopes are fertile material but not fissile and also have a lower overall probability (cross section) of neutron capture; therefore, they tend to accumulate in nuclear fuel used in a thermal reactor, the design of nearly all [[Engineering:Nuclear power plant|nuclear power plant]]s today. In plutonium that has been used a second time in thermal reactors in [[Physics:MOX fuel|MOX fuel]], <sup>240</sup>Pu may even be the most common isotope. All plutonium isotopes and other [[Chemistry:Actinide|actinide]]s, however, are fissionable with fast neutrons. <sup>240</sup>Pu does have a moderate thermal neutron absorption cross section, so that <sup>241</sup>Pu production in a thermal reactor becomes a significant fraction as large as <sup>239</sup>Pu production.

<sup>241</sup>Pu has a half-life of 14 years, and has slightly higher thermal neutron cross sections than <sup>239</sup>Pu for both fission and absorption. While nuclear fuel is being used in a reactor, a <sup>241</sup>Pu nucleus is much more likely to fission or to capture a neutron than to decay. <sup>241</sup>Pu accounts for a significant proportion of fissions in thermal reactor fuel that has been used for some time. However, in [[Physics:Spent nuclear fuel|spent nuclear fuel]] that does not quickly undergo nuclear reprocessing but instead is cooled for years after use, much or most of the <sup>241</sup>Pu will beta decay to [[Physics:Americium-241|americium-241]], one of the [[Chemistry:Minor actinide|minor actinide]]s, a strong alpha emitter, and difficult to use in thermal reactors.

<sup>242</sup>Pu has a particularly low cross section for thermal neutron capture; and it takes three neutron absorptions to become another fissile isotope (either [[Chemistry:Curium|curium]]-245 or <sup>241</sup>Pu) and fission. Even then, there is a chance either of those two fissile isotopes will fail to fission but instead absorb a fourth neutron, becoming curium-246 (on the way to even heavier actinides like [[Chemistry:Californium|californium]], which is a neutron emitter by spontaneous fission and difficult to handle) or becoming <sup>242</sup>Pu again; so the mean number of neutrons absorbed before fission is even higher than 3. Therefore, <sup>242</sup>Pu is particularly unsuited to recycling in a thermal reactor and would be better used in a [[Physics:Fast reactor|fast reactor]] where it can be fissioned directly. However, <sup>242</sup>Pu's low cross section means that relatively little of it will be transmuted during one cycle in a thermal reactor. <sup>242</sup>Pu's half-life is about 15 times as long as <sup>239</sup>Pu's half-life; therefore, it is 1/15 as radioactive and not one of the larger contributors to [[Physics:Nuclear waste|nuclear waste]] radioactivity.
<sup>242</sup>Pu's [[Physics:Gamma ray|gamma ray]] emissions are also weaker than those of the other isotopes.<ref>{{cite web|url=http://www.wmsym.org/archives/2001/21B/21B-18.pdf|title=Plutonium Isotopic Results of Known Samples Using the Snap Gamma Spectroscopy Analysis Code and the Robwin Spectrum Fitting Routine|access-date=2013-03-15|archive-date=2017-08-13|archive-url=https://web.archive.org/web/20170813191754/http://www.wmsym.org/archives/2001/21B/21B-18.pdf|url-status=dead}}</ref>

<sup>243</sup>Pu has a half-life of only 5 hours, beta decaying to [[Physics:Americium-243|americium-243]]. Because <sup>243</sup>Pu has little opportunity to capture an additional neutron before decay, the [[Physics:Nuclear fuel cycle|nuclear fuel cycle]] does not produce the long-lived <sup>244</sup>Pu in significant quantity.

<sup>238</sup>Pu is not normally produced in as large quantity by the nuclear fuel cycle, but some is produced from [[Physics:Neptunium-237|neptunium-237]] by neutron capture (this reaction can also be used with purified neptunium to produce <sup>238</sup>Pu relatively free of other plutonium isotopes for use in [[Physics:Radioisotope thermoelectric generator|radioisotope thermoelectric generator]]s), by the (n,2n) reaction of fast neutrons on <sup>239</sup>Pu, or by alpha decay of [[Chemistry:Curium|curium]]-242, which is produced by neutron capture from <sup>241</sup>Am. It has significant thermal neutron cross section for fission, but is more likely to capture a neutron and become <sup>239</sup>Pu.

==Manufacture==<!-- This section is linked from [[Physics:Radioactive waste|Radioactive waste]] -->

===Plutonium-240, -241 and -242===

The fission [[Physics:Cross section|cross section]] for <sup>239</sup>Pu is 747.9 [[Physics:Barn (unit)|barns]] for thermal neutrons, while the activation cross section is 270.7 barns (the ratio approximates to 11 fissions for every 4 neutron captures). The higher plutonium isotopes are created when the uranium fuel is used for a long time. For high burnup used fuel, the concentrations of the higher plutonium isotopes will be higher than the low burnup fuel that is reprocessed to obtain weapons grade plutonium.

{| class="wikitable"
|+ The formation of <sup>240</sup>Pu, <sup>241</sup>Pu, and <sup>242</sup>Pu from <sup>238</sup>U
!rowspan="2"| Isotope !!colspan="2"|Thermal neutron<br/>cross section<ref>National Nuclear Data Center [http://www.nndc.bnl.gov/chart/ Interactive Chart of Nuclides] {{Webarchive|url=https://web.archive.org/web/20110721051025/http://www.nndc.bnl.gov/chart/ |date=2011-07-21 }}</ref><br/>(barns) !!rowspan="2"| Decay<br/>Mode !! rowspan="2"|Half-life
|-
! Capture !! Fission
|-
| [[Physics:Uranium-238|<sup>238</sup>U]] || 2.683 || 0.000 || α || 4.468 x 10<sup>9</sup> years
|-
| [[Physics:Uranium-239|<sup>239</sup>U]] || 20.57 || 14.11 || β<sup>−</sup> || 23.45 minutes
|-
| [[Physics:Neptunium-239|<sup>239</sup>Np]] || 77.03 || – || β<sup>−</sup> || 2.356 days
|-
| [[Physics:Plutonium-239|<sup>239</sup>Pu]] || 270.7 || 747.9 || α || 24,110 years
|-
| [[Physics:Plutonium-240|<sup>240</sup>Pu]] || 287.5 || 0.064 || α || 6,561 years
|-
| [[Physics:Plutonium-241|<sup>241</sup>Pu]] || 363.0 || 1012 || β<sup>−</sup> || 14.325 years
|-
| [[Physics:Plutonium-242|<sup>242</sup>Pu]] || 19.16 || 0.001 || α || 373,300 years
|}

===Plutonium-239===
{{Main|Physics:Plutonium-239}}
Plutonium-239 is one of the three fissile materials used for the production of nuclear weapons and in some nuclear reactors as a source of energy. The other fissile materials are [[Physics:Uranium-235|uranium-235]] and [[Physics:Uranium-233|uranium-233]]. Plutonium-239 is virtually nonexistent in nature. It is made by bombarding [[Physics:Uranium-238|uranium-238]] with neutrons in a nuclear reactor. Uranium-238 is present in quantity in most reactor fuel; hence plutonium-239 is continuously made in these reactors. Since plutonium-239 can itself be split by neutrons to release energy, plutonium-239 provides a portion of the energy generation in a nuclear reactor.
[[File:Plutonium ring.jpg|right|300px|thumb|A ring of weapons-grade electrorefined plutonium, with 99.96% purity. This 5.3 kg ring is enough plutonium for use in an efficient nuclear weapon. The ring shape is needed to depart from a spherical shape and avoid [[Physics:Critical mass|criticality]].]]

{| class="wikitable"
|+ The formation of <sup>239</sup>Pu from <sup>238</sup>U<ref name="Miner1968p541">{{harvnb|Miner|1968|p=541}}</ref>
! Element !! Isotope !! Thermal neutron capture<br/>cross section (barn) !! Thermal neutron fission <br/>Cross section (barn) !! decay mode !! Half-life
|-
! [[Chemistry:Uranium|U]]
| 238 || 2.68 || 5·10<sup>−6</sup> || α || 4.47 x 10<sup>9</sup> years
|-
! [[Chemistry:Uranium|U]]
| 239 || 22 || 15 || β<sup>−</sup> || 23 minutes
|-
! [[Chemistry:Neptunium|Np]]
| 239 || 30 || 1 || β<sup>−</sup> || 2.36 days
|-
! [[Chemistry:Plutonium|Pu]]
| 239 || 271 || 750 || α || 24,110 years
|}

===Plutonium-238===
{{Main|Physics:Plutonium-238}}
There are small amounts of <sup>238</sup>Pu in the plutonium of usual plutonium-producing reactors. However, isotopic separation would be quite expensive compared to another method: when a  <sup>235</sup>U atom captures a neutron, it is converted to an excited state of <sup>236</sup>U. Some of the excited <sup>236</sup>U nuclei undergo fission, but some decay to the ground state of <sup>236</sup>U by emitting gamma radiation. Further neutron capture creates <sup>237</sup>U, which has a half-life of 7 days and thus quickly decays to <sup>237</sup>Np. Since nearly all neptunium is produced in this way or consists of isotopes that decay quickly, one gets nearly pure <sup>237</sup>Np by chemical separation of neptunium. After this chemical separation, <sup>237</sup>Np is again irradiated by reactor neutrons to be converted to <sup>238</sup>Np, which decays to <sup>238</sup>Pu with a half-life of 2 days.

{| class="wikitable"
|+ The formation of <sup>238</sup>Pu from <sup>235</sup>U
! Element !! Isotope !! Thermal neutron<br/>cross section !! decay mode !! Half-life
|-
! [[Chemistry:Uranium|U]]
| 235 || 99 || α || 703,800,000 years
|-
! [[Chemistry:Uranium|U]]
| 236 || 5.3 || α || 23,420,000 years
|-
! [[Chemistry:Uranium|U]]
| 237 || — || β<sup>−</sup> || 6.75 days
|-
! [[Chemistry:Neptunium|Np]]
| 237 || 165 (capture) || α || 2,144,000 years
|-
! [[Chemistry:Neptunium|Np]]
| 238 || — || β<sup>−</sup> || 2.11 days
|-
! [[Chemistry:Plutonium|Pu]]
| 238 || — || α || 87.7 years
|}

==Plutonium-240 as an obstacle to nuclear weapons==
[[Physics:Plutonium-240|Plutonium-240]] undergoes spontaneous fission as a secondary decay mode at a small but significant rate ({{val|5.8|e=-6}}%).{{NUBASE2020|ref}} The presence of <sup>240</sup>Pu limits the plutonium's use in a nuclear bomb, because the neutron flux from spontaneous fission initiates the [[Philosophy:Chain reaction|chain reaction]] prematurely, causing an early release of energy that physically disperses the core before full [[Physics:Implosion (mechanical process)|implosion]] is reached. This prevents most of the core from participation in the chain reaction and reduces the bomb's power.

Plutonium consisting of more than about 90% <sup>239</sup>Pu is called [[Physics:Weapons-grade plutonium|weapons-grade plutonium]]; plutonium from [[Physics:Spent nuclear fuel|spent nuclear fuel]] from commercial power reactors generally contains at least 20% <sup>240</sup>Pu and is called [[Physics:Reactor-grade plutonium|reactor-grade plutonium]]. However, modern nuclear weapons use fusion boosting, which mitigates the predetonation problem; if the [[Physics:Pit (nuclear weapon)|pit]] can generate a [[Physics:Nuclear weapon yield|nuclear weapon yield]] of even a fraction of a kiloton, which is enough to start [[Physics:Nuclear fusion|deuterium–tritium fusion]], the resulting burst of neutrons will fission enough plutonium to ensure a yield of tens of kilotons.

Contamination due to <sup>240</sup>Pu is the reason plutonium weapons must use the [[Engineering:Nuclear weapon design#Implosion-type weapon|implosion method]]. Theoretically, pure <sup>239</sup>Pu could be used in a gun-type nuclear weapon, but achieving this level of purity is prohibitively difficult. Plutonium-240 contamination has proven a mixed blessing to nuclear weapons design. While it created delays and headaches during the [[Physics:Manhattan Project|Manhattan Project]] because of the need to develop implosion technology, those same difficulties are currently a barrier to nuclear proliferation. Implosion devices are also inherently more efficient and less prone to accidental detonation than are gun-type weapons.

== References ==
* Isotope masses from:
**{{NUBASE 2003 |ref=none}}
* Isotopic compositions and standard atomic masses from:
**{{CIAAW 2005 |ref=none}}
* Half-life, spin, and isomer data selected from the following sources.
**{{NUBASE 2003 |ref=none}}
**{{NNDC |ref=none}}
**{{CRC85|chapter=11 |ref=none}}

{{Reflist}}

==Sources==
* {{Cite book |url=https://www-nds.iaea.org/publications/indc/indc_usa_0085_II.pdf |title=Proceedings of the conference on nuclear data evaluation methods and procedures. BNL-NCS 51363. |date=1981 |publisher=[[Organization:Brookhaven National Laboratory|Brookhaven National Laboratory]] |editor-last=Magurno |editor-first=B. A. |volume=II |location=Upton |access-date=August 6, 2014 |editor-last2=Pearlstein |editor-first2=S. |archive-url=https://web.archive.org/web/20210308125416/https://www-nds.iaea.org/publications/indc/indc_usa_0085_II.pdf |archive-date=March 8, 2021 |url-status=live}}
* {{Cite book |last1=Miner |first1=William N. |title=The Encyclopedia of the Chemical Elements |last2=Schonfeld, Fred W. |publisher=Reinhold Book Corporation |year=1968 |editor-last=Clifford A. Hampel |location=New York (NY) |pages=[https://archive.org/details/encyclopediaofch00hamp/page/540 540–546] |chapter=Plutonium |lccn=68029938 |ref=CITEREFMiner1968 |chapter-url=https://archive.org/details/encyclopediaofch00hamp |chapter-url-access=registration}}

{{Navbox element isotopes}}
{{Isotopes of plutonium}}

[[Category:Isotopes of plutonium| ]]
[[Category:Plutonium]]
[[Category:Lists of isotopes by element|Plutonium]]

{{Sourceattribution|Isotopes of plutonium}}