Editing Nuclear weapon design (section)

=== Minor actinide fission weapons ===
{{multiple image|perrow = 2|total_width=350
| image1 = Np_sphere.jpg
| image2 = Americium_microscope.jpg
| caption1 = Macroscopic shell of neptunium-237
| caption2 = Microscopic quantity of americium
| footer = [[Minor actinides]] of concern to hypothetical fission weapons
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Some isotopes of [[protactinium]], [[neptunium]], [[americium]], [[curium]], [[californium]], [[berkelium]], and [[einsteinium]] have calculated [[critical mass]] values, ranging in the kilograms to tens of kilograms. Few possess an adequate combination of high [[fission cross section]] (for detonation), low [[spontaneous fission]] rate (to limit [[predetonation]]), low alpha or gamma decay rate (to allow handling).{{Citation needed|date=April 2025}}

All suffer from a far higher cost of production compared to standard [[fissile material]]. This is due to both production of the quantity required, often in [[High flux reactor|high flux reactors]], and complex chemical separation procedures. For elements curium and, total global production has never exceeded a single critical mass of separated material.{{Citation needed|date=April 2025}}

[[Neptunium-237]] is considered the most immediately concerning minor actinide isotope for weaponization. Comprising ~0.05% of [[spent nuclear fuel]], ~5 tons are produced annually worldwide. The [[International Atomic Energy Agency]] has established monitoring for facilities capable of separation of the isotope, but is yet to classify it as a "special fissionable material", alongside [[plutonium-239]], and high enrichments of [[uranium-235]] and [[uranium-233]].<ref name="c496">{{cite web |last=An |first=J S |last2=Shin |first2=J S |last3=Kim |first3=J S |last4=Kwack |first4=E H |last5=Kim |first5=B K |date=2000-05-01 |title=The proliferation potential of neptunium and americium |url=https://www.osti.gov/etdeweb/biblio/20101205 |access-date=2025-04-30 |website=The proliferation potential of neptunium and americium (Technical Report)}}</ref> In September 2002, researchers at the [[Los Alamos National Laboratory]] briefly produced the first known nuclear [[critical mass]] involving a significant quantity of neptunium, in combination with shells of [[enriched uranium]] ([[uranium-235]]), discovering that the critical mass of a bare sphere of neptunium-237 "ranges from kilogram weights in the high fifties to low sixties,"<ref name="criticality">{{cite web |last1=Sanchez |first1=Rene G. |last2=Loaiza |first2=David J. |last3=Kimpland |first3=Robert H. |last4=Hayes |first4=David K. |last5=Cappiello |first5=Charlene C. |last6=Myers |first6=William L. |last7=Jaegers |first7=Peter J. |last8=Clement |first8=Steven D. |last9=Butterfield |first9=Kenneth B. |title=Criticality of a <sup>237</sup>Np Sphere |url=http://typhoon.jaea.go.jp/icnc2003/Proceeding/paper/2.14_107.pdf |url-status=dead |archive-url=https://web.archive.org/web/20140512214219/http://typhoon.jaea.go.jp/icnc2003/Proceeding/paper/2.14_107.pdf |archive-date=2014-05-12 |access-date=2014-08-06 |publisher=Japanese Atomic Energy Agency}}</ref> showing that it "is about as good a bomb material as [uranium-235]."<ref name="Weiss">{{cite journal |last=Weiss |first=Peter |date=2 July 2009 |title=Neptunium nukes?: Little-studied metal goes critical |journal=Science News |volume=162 |issue=17 |pages=259 |doi=10.2307/4014034 |jstor=4014034}}</ref> The United States federal government made plans in March 2004 to move America's supply of separated neptunium to a nuclear-waste disposal site in [[Nevada]].<ref name="Nevada">{{cite web |last=Yarris |first=Lynn |date=2005-11-29 |title=Getting the Neptunium out of Nuclear Waste |url=http://newscenter.lbl.gov/feature-stories/2005/11/29/getting-the-neptunium-out-of-nuclear-waste/ |access-date=2014-07-26 |publisher=Berkeley laboratory, U.S. Department of Energy}}</ref>

Certain isotopes of [[americium]] are also considered weaponizable, despite considerable challenge, based on the testimony of nuclear weapons physicists.<ref name="s816">{{cite journal |last=Pellaud |first=Bruno |date=2002-07-12 |title=Proliferation aspects of plutonium recycling |url=https://comptes-rendus.academie-sciences.fr/physique/item/10.1016/S1631-0705(02)01364-6.pdf |journal=Comptes Rendus. Physique |publisher=Cellule MathDoc/Centre Mersenne |volume=3 |issue=7-8 |pages=1067–1079 |doi=10.1016/s1631-0705(02)01364-6 |issn=1878-1535 |access-date=2025-04-30 |doi-access=free}}</ref>