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{{redirect|Pu||PU (disambiguation)}}
{{about|the radioactive element}}
{{infobox plutonium}} 
'''Plutonium''' ({{pronEng|pluːˈtoʊniəm}}, symbol '''Pu''', [[atomic number]]—or element—94) is a rare [[transuranic]] [[radioactive]] [[chemical element|element]]. It is an [[actinide]] [[metal]] of silvery-white appearance that [[tarnish]]es when exposed to air, forming a dull coating when [[plutonium(IV) oxide|oxidized]]. The element normally exhibits six [[allotrope]]s and four [[oxidation state]]s. It reacts with [[carbon]], [[halogen]]s, [[nitrogen]] and [[silicon]]. When exposed to moist air, it forms [[oxide]]s and [[hydride]]s that expand the sample up to 70% in volume, which in turn flake off as a powder that can [[pyrophoricity|spontaneously ignite]]. It is also a [[Radiation poisoning|radioactive poison]] that accumulates in [[bone marrow]]. These and other properties make the handling of plutonium dangerous, although its overall toxicity is sometimes overstated.

*[[Plutonium-238]] has a half-life of 88&nbsp;years and emits [[alpha particle]]s. It is a heat source in [[radioisotope thermoelectric generator]]s, which are used to power some [[spacecraft]]. Pu-238 is formed in several ways, but pure Pu-238 for RTGs is produced by neutron capture on [[neptunium-237]].
*[[Plutonium-239]] is the most important [[isotope]] of plutonium, with a [[half-life]] of 24,100&nbsp;years. Pu-239 and Pu-241 are [[fissile]], meaning that the nuclei of its atoms can [[nuclear fission|break apart]] by being bombarded by [[neutron temperature|slow moving]] [[thermal neutron]]s, releasing energy, [[gamma radiation]] and [[neutron radiation|more neutrons]]. It can therefore sustain a [[nuclear chain reaction]], leading to applications in [[nuclear weapon]]s and [[nuclear reactor]]s. Pu-239 is synthesized by irradiating [[uranium-238]] with neutrons in a [[nuclear reactor]], then recovered via [[nuclear reprocessing]] of the fuel. Further [[neutron capture]] produces successively heavier isotopes. 
*[[Plutonium-240]] has a high rate of [[spontaneous fission]], raising the background [[neutron radiation]] of plutonium containing it. Plutonium is graded by proportion of Pu-240: [[weapons grade]] (<&nbsp;7%), [[fuel grade]] (7–19%) and [[reactor grade]] (>&nbsp;19%). Lower grades are less suited for [[nuclear weapon]]s and [[thermal reactor]]s but can fuel [[fast reactor]]s. Pu-240 is not fissile, but is [[fertile material]] like U-238.
*[[Plutonium-241]] is fissile, but also [[beta decay]]s with a halflife of 14 years to [[americium-241]].
*[[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 halflife than any of the lighter isotopes.
*[[Plutonium-244]] is the most stable [[isotopes of plutonium|isotope of plutonium]], with a half-life of about 80&nbsp;million years, long enough to be found in trace quantities in nature. 


Element 94 was first synthesized in 1940 by a team led by [[Glenn T. Seaborg]] and [[Edwin McMillan]] at a [[University of California, Berkeley]] laboratory by bombarding [[uranium-238]] with [[deuteron]]s. McMillan named the new element after [[Pluto]], and Seaborg suggested the symbol Pu as a joke. Trace amounts of plutonium were subsequently discovered in nature. Discovery of plutonium became a classified part of the [[Manhattan Project]] to develop an atomic bomb during [[World War II]]. The first [[nuclear test]], "[[Trinity (nuclear test)|Trinity]]" (July 1945), and the second atomic bomb used to destroy a city ([[Atomic bombings of Hiroshima and Nagasaki|Nagasaki, Japan, in August 1945]]), "[[Fat Man]]", both had cores of Pu-239. [[Human radiation experiments]] studying plutonium were conducted without [[informed consent]], and a number of [[criticality accident]]s, some lethal, occurred during and after the war. Disposal of [[nuclear waste|plutonium waste]] from [[nuclear power plant]]s and [[nuclear disarmament|dismantled nuclear weapons]] built during the [[Cold War]] is a major [[nuclear proliferation|nuclear-proliferation]], health, and environmental concern. Other sources of [[plutonium in the environment]] are [[nuclear fallout|fallout]] from numerous above-ground nuclear tests (now [[Partial Test Ban Treaty|banned]]) and several [[nuclear accident]]s.

== Characteristics ==
=== Physical ===
Plutonium, like most metals, has a bright silvery appearance at first, much like [[nickel]], but it [[plutonium(IV) oxide|oxidizes]] very quickly to a dull gray, although yellow and olive green are also reported.<ref name = "WISER">
{{cite web
 | url = http://webwiser.nlm.nih.gov/getSubstanceData.do;jsessionid=89B673C34252C77B4C276F2B2D0E4260?substanceID=419&displaySubstanceName=Plutonium,%20Radioactive&UNNAID=&STCCID=&selectedDataMenuItemID=44
 | author = NIH contributors
 | publisher = U.S. National Library of Medicine, National Institutes of Health
 | location = Bethesda (MD)
 | title = Plutonium, Radioactive
 | work = Wireless Information System for Emergency Responders (WISER)
 | accessdate = 2008-11-23
}} (public domain text)</ref><ref>
{{cite journal
 | title = Nitric acid processing
 | url = http://arq.lanl.gov/source/orgs/nmt/nmtdo/AQarchive/3rdQuarter08/page3.shtml
 | journal = Actinide Research Quarterly
 | author = ARQ staff
 | year = 2008
 | issue = 3rd quarter
 | publisher = Los Alamos National Laboratory
 | location = Los Alamos (NM)
 | quote =While plutonium dioxide is normally olive green, samples can be various colors. It is generally believed that the color is a function of chemical purity, stoichiometry, particle size, and method of preparation, although the color resulting from a given preparation method is not always reproducible.
 | accessdate =2009-02-15}}</ref> At room temperature plutonium is in its [[allotropes of plutonium|α form]] (''alpha''). This, the most common structural form of the element ([[allotrope]]), is about as hard and brittle as [[Cast iron#Grey cast iron|grey cast iron]] unless it is [[alloy]]ed with other metals to make it soft and ductile.<ref name = "WISER"/> Unlike most metals, it is not a good conductor of [[thermal conductivity|heat]] or [[electrical conductivity|electricity]].<ref name = "WISER"/> It has a low [[melting point]] (640&nbsp;°C) and an unusually high [[boiling point]] (3,327&nbsp;°C).<ref name = "WISER"/>

[[alpha decay|Alpha particle emission]], which is the release of high-energy [[helium]] nuclei, is the most common form of [[ionizing radiation|radiation]] given off by plutonium.<ref name = "NNDC"/> Heat given off by the release of and deceleration of these alpha particles make a mass of plutonium the size of a [[softball]] warm to the touch while a somewhat larger mass can boil a [[liter]] of water in a few minutes, although this varies with isotopic composition.<ref name = "Heiserman1992"/>{{inote|page 338}}<ref>
{{cite book
 | last = Rhodes |first = Richard
 | year = 1986
 | title = The Making of the Atomic Bomb
 | isbn = 0-671-65719-4
 | pages = 659–660
 | publisher = Simon & Schuster
 | location = New York
}} Leona Marshall: "When you hold a lump of it in your hand, it feels warm, like a live rabbit"</ref>

[[Resistivity]] is a measure of how strongly a material opposes the flow of [[electric current]]. The resistivity of plutonium at room temperature is very high for a metal, and it gets even higher with lower temperatures, which is unusual for metals.<ref name = "Miner1968p544"/> This trend continues down to 100&nbsp;[[Kelvin|K]], below which resistivity rapidly decreases for fresh samples.<ref name = "Miner1968p544"/> Resistivity then begins to increase with time at around 20&nbsp;K due to radiation damage, with the rate dictated by the isotopic composition of the sample.<ref name = "Miner1968p544"/>

Due to self-irradiation, a sample of plutonium fatigues throughout its crystal structure, meaning the ordered arrangement of its atoms becomes disrupted by radiation with time.<ref name = "HeckerPlutonium" /> However, self-irradiation can also lead to [[Annealing (metallurgy)|annealing]] which counteracts some of the fatigue effects as temperature increases above 100&nbsp;K.<ref>
{{cite journal
 | title = Aging of Plutonium and Its Alloys
 | page = 242
 | journal = Los Alamos Science
 | year = 2000
 | issue = 26
 | url = http://library.lanl.gov/cgi-bin/getfile?00818029.pdf
 | format = PDF
 | last = Hecker
 | first = Siegfried S.
 | coauthors = Martz, Joseph C.
 | location = Los Alamos, New Mexico
 | publisher = Los Alamos National Laboratory
 | accessdate = 2009-02-15
 }}</ref>

=== Allotropes ===
{{main|Allotropes of plutonium}}
[[Image:Pu-phases.png|thumb|Plutonium has six allotropes at ambient pressure: '''alpha'''&nbsp;(&alpha;), '''beta'''&nbsp;(&beta;), '''gamma'''&nbsp;(&gamma;), '''delta'''&nbsp;(&delta;), '''delta&nbsp;prime'''&nbsp;(&delta;&prime;), & '''epsilon'''&nbsp;(&epsilon;)<ref name = "Baker1983"/>]]</div>
Plutonium normally has six [[allotrope]]s and forms a seventh (zeta, ζ) at high temperature within a limited pressure range.<ref name = "Baker1983">
{{cite journal
 | url = http://library.lanl.gov/cgi-bin/getfile?07-16.pdf
 | title = Plutonium: A Wartime Nightmare but a Metallurgist's Dream
 | last = Baker
 | first = Richard D.
 | coauthors = Hecker, Siegfried S.; Harbur, Delbert R.
 | journal = Los Alamos Science
 | year = 1983
 | publisher = Los Alamos National Laboratory
 | pages = 148, 150–151
 | accessdate = 2009-02-15
}}</ref>{{inote|page 148}} These allotropes, which are different structural modifications or forms of an element, have very similar [[internal energy|internal energies]] but significantly varying [[density|densities]] and [[crystal structure]]s. This makes plutonium very sensitive to changes in temperature, pressure, or chemistry, and allows for dramatic volume changes following [[phase transition]]s from one allotropic form to another.<ref name = "HeckerPlutonium">
{{cite journal
 | first = Siegfried S.
 | last = Hecker
 | title = Plutonium and its alloys: from atoms to microstructure
 | journal = Los Alamos Science
 | volume = 26
 | year = 2000
 | pages = 290–335
 | url = http://www.fas.org/sgp/othergov/doe/lanl/pubs/00818035.pdf
 | format = PDF
 | accessdate = 2009-02-15
}}</ref> Unlike most materials, plutonium ''increases'' in density when it melts, by 2.5%, but the liquid metal exhibits a linear decrease in density with temperature.<ref name="Miner1968p544">{{harvnb|Miner|1968|p = 544}}</ref> Densities of the different allotropes vary from 16.00&nbsp;g/cm<sup>3</sup> to 19.86&nbsp;g/cm<sup>3</sup>.<ref name="CRC2006p4-27" />

The presence of these many allotropes makes machining plutonium very difficult, as it changes state very readily. For example, the α form exists at room temperature in unalloyed plutonium. It has machining characteristics similar to [[cast iron]] but changes to the plastic and malleable β form (''beta'') at slightly higher temperatures.<ref name = "Miner1968p542"/> The reasons for the complicated phase diagram are not entirely understood. The α form has a low-symmetry [[monoclinic crystal system|monoclinic]] structure, hence its brittleness, strength, compressibility, and poor conductivity.<ref name = "Baker1983"/>

Plutonium in the δ form (''delta'') normally exists in the 310&nbsp;°C to 452&nbsp;°C range but is stable at room temperature when alloyed with a small percentage of [[gallium]], [[aluminium]], or [[cerium]], enhancing workability and allowing it to be [[welding|welded]].<ref name = "Miner1968p542"/> The delta form has more typical metallic character, and is roughly as strong and malleable as aluminium.<ref name = "Baker1983"/><!-- NEEDS CITE In fission weapons, the explosive [[shock wave]]s used to compress a plutonium core will also cause a transition from the usual delta phase plutonium to the denser alpha form, significantly helping to achieve [[supercriticality]]. /NEEDS CITE -->

=== Nuclear fission ===
Plutonium is a radioactive [[actinide]] metal whose [[isotope]], [[plutonium-239]] (Pu-239), is one of the three primary [[fissile]] isotopes<ref name = "Stwertka1998"/> ([[uranium-233]] and [[uranium-235]] are the other two).<ref>
{{cite web
 | url = http://www.epa.gov/rpdweb00/glossary/termdef.html#f
 | title = Fissile Material
 | work = Radiation Glossary
 | publisher = United States Environmental Protection Agency
 | year = 2008
 | accessdate = 2008-11-23
 | author = EPA contributors
}}</ref> 
[[Pu-241]] is also highly fissile.
To be considered fissile, an isotope's [[atomic nucleus]] must be able to break apart or [[nuclear fission|fission]] when struck by a [[neutron temperature|slow moving neutron]], and to release enough additional neutrons in the process to sustain the [[nuclear chain reaction]] by splitting further nuclei.

[[Image:Plutonium ring.jpg|left|100px|thumb|Weapons-grade electrorefined plutonium]]
Pu-239 has a [[Four factor formula|multiplication factor]] (k) larger than one, which means that if the metal is present in sufficient mass and with an appropriate geometry (e.g., a compressed sphere), it can form a [[critical mass]].<ref>
{{cite book
 | title = Understanding Physics
 | last = Asimov
 | first = Isaac
 | authorlink = Isaac Asimov
 | page = 905
 | chapter = Nuclear Reactors
 | year = 1988
 | isbn = 0880292512
 | publisher = Barnes & Noble Publishing
 }}</ref> During fission, a fraction of the [[binding energy]], which holds a nucleus together, is released as a large amount of thermal, electromagnetic and kinetic energy; a kilogram of Pu-239 can produce an explosion equivalent to 20,000&nbsp;tons of [[Trinitrotoluene|TNT]].<ref name = "Heiserman1992"/> It is this energy that makes Pu-239 useful in [[nuclear weapon]]s and [[nuclear reactor|reactors]].

The presence of the isotope [[plutonium-240]] (Pu-240) in a sample limits its nuclear bomb potential, as Pu-240 has a relatively high [[spontaneous fission]] rate (~440 fissions per second per gram—over 1,000 neutrons per second per gram<ref>Samuel Glasstone and Leslie M. Redman, ''[http://www.doeal.gov/opa/docs/RR00171.pdf An Introduction to Nuclear Weapons]'' (Atomic Energy Commission Division of Military Applications Report WASH-1038, June 1972), p. 12.</ref>), raising the background neutron levels and thus increasing the risk of [[fizzle|predetonation]].<ref>
{{cite book
 | title = The Manhattan Project: Making the Atomic Bomb
 | publisher = United States Department of Energy
 | id = DOE/MA-0001-01/99
 | location = Oak Ridge (TN)
 | last = Gosling
 | first = F.G.
 | page = 40
 | url = http://www.cfo.doe.gov/me70/manhattan/publications/DE99001330.pdf
 | year = 1999
 | accessdate = 2009-02-15
}}</ref> Plutonium is identified as either weapon grade, fuel grade, or power reactor grade based on the percentage of Pu-240 that it contains. Weapon grade plutonium contains less than 7% Pu-240. Fuel grade plutonium contains from 7 to less than 19%, and power reactor grade contains 19% or more Pu-240.<ref>
{{cite book
 | title = Plutonium: The First 50 Years
 | publisher = U.S. Department of Energy
 | year = 1996
 | id = DOE/DP-1037
 | author = DOE contributors
 | url = http://www.doeal.gov/SWEIS/DOEDocuments/004%20DOE-DP-0137%20Plutonium%2050%20Years.pdf
}} (public domain text)</ref> The isotope [[plutonium-238]] (Pu-238) is not fissile but can undergo nuclear fission easily with [[fast neutrons]] as well as [[alpha decay]].<ref name = "Heiserman1992"/>

=== Isotopes and synthesis ===
{{main|Isotopes of plutonium}}
Twenty [[radioisotope|radioactive isotopes]] of plutonium have been characterized.<ref name = "NNDC">
{{cite web
 | url = http://www.nndc.bnl.gov/chart/
 | author = NNDC contributors
 | editor = Alejandro A. Sonzogni (Database Manager)
 | title = Chart of Nuclides
 | publisher = National Nuclear Data Center, [[Brookhaven National Laboratory]]
 | accessdate = 2008-09-13
 | year = 2008
 | location = Upton (NY)
}}</ref> The longest-lived are Pu-244, with a half-life of 80.8 million years, Pu-242, with a half-life of 373,300&nbsp;years, and Pu-239, with a half-life of 24,110&nbsp;years.<ref name = "NNDC"/> All of the remaining radioactive isotopes have half-lives that are less than 7,000&nbsp;years.<ref name = "NNDC"/> This element also has eight [[meta state|metastable states]], though none are stable and all have half-lives less than one second.<ref name = "NNDC"/>

The isotopes of plutonium range in [[mass number]] from 228 to 247.<ref name = "NNDC"/> The primary [[radioactive decay|decay modes]] of isotopes with mass numbers lower than the most stable isotope, Pu-244, are [[spontaneous fission]] and [[alpha emission|α emission]], mostly forming uranium (92 [[proton]]s) and [[neptunium]] (93 protons) isotopes as [[decay product]]s (neglecting the wide range of daughter nuclei created by fission processes).<ref name = "NNDC"/>  The primary decay mode for isotopes with mass numbers higher than Pu-244 is [[beta emission|β emission]], mostly forming [[americium]] (95 protons) isotopes as decay products.<ref name = "NNDC"/> Pu-241 is the [[parent isotope]] of the [[neptunium decay series]], decaying to americium-241 via β or electron emission.<ref name = "Heiserman1992"/>{{inote|page 340}}

Pu-238 and Pu-239 are the most-widely synthesized isotopes.<ref name = "Heiserman1992"/> Pu-239 is synthesized via the following reaction using uranium (U) and neutrons (n) via beta decay (β<sup>−</sup>) with neptunium (Np) as an intermediate:<ref>{{cite journal | first=J. W. | last=Kennedy | coauthors=Seaborg, G. T.; Segrè, E.; Wahl, A. C. | title=Properties of Element 94 | journal=Physical Review | year=1946 | issue=7–8 | pages=555–556 | doi=10.1103/PhysRev.70.555 | volume=70 }}</ref>

:<math>\mathrm{^{238}_{\ 92}U\ +\ ^{1}_{0}n\ \longrightarrow \ ^{239}_{\ 92}U\ \xrightarrow[23.5 \ min]{\beta^-} \ ^{239}_{\ 93}Np\ \xrightarrow[2.3565 \ d]{\beta^-} \ ^{239}_{\ 94}Pu}</math>

In other words, neutrons from the fission of U-235 are [[neutron capture|captured]] by U-238 nuclei to form U-239; a [[beta decay]] converts a neutron into a proton to form Np-239 (half-life 2.36&nbsp;days) and another beta decay forms Pu-239.<ref name = "Greenwood1997p1259">{{harvnb|Greenwood|1997|p = 1259}}</ref> Workers on the [[Tube Alloys]] project had predicted this reaction theoretically in 1940.

Pu-238 is synthesized by bombarding U-238 with [[deuteron]]s (D, the nuclei of heavy [[hydrogen]]) in the following reaction:<ref>{{cite journal | first=Glenn T. | last=Seaborg | coauthors=McMillan, E.; Kennedy,  J. W.; Wahl, A. C. | title=Radioactive Element 94 from Deuterons on Uranium | journal=Physical Review | year=1946 | issue=7–8 | pages=366–367 | doi=10.1103/PhysRev.69.367 | volume=69 }}</ref>

:<math>\mathrm{^{238}_{\ 92}U\ +\ ^{2}_{1}D\ \longrightarrow \ ^{238}_{\ 93}Np\ +\ 2\ ^{1}_{0}n \quad;\quad ^{238}_{\ 93}Np\ \xrightarrow[2.117 \ d]{\beta^-} \ ^{238}_{\ 94}Pu}</math>

In this equation, a deuteron hitting U-238 produces two neutrons and Np-238. The Np-238 spontaneously decays by emitting negative beta particles to form Pu-238.

=== Compounds and chemistry ===
{{see also|:Category:Plutonium compounds|l1 = Plutonium compounds}}
[[Image:Plutonium in solution.jpg|thumb|right|300px|Various oxidation states of Pu in solution]]
At room temperature, pure plutonium is silvery in color but gains a tarnish when oxidized.<ref name = "Heiserman1992"/>{{inote|page 339; ref for alpha form, which is the most common at room temps}} The element displays four common ionic [[oxidation state]]s in [[aqueous solution]] and one rare one:<ref name = "CRC2006p4-27"/>
* Pu(III), as Pu<sup>3+</sup> (blue lavender)
* Pu(IV), as Pu<sup>4+</sup> (yellow brown)
* Pu(V), as PuO<sub>2</sub><sup>+</sup> (pink?)<ref group = note>The PuO<sub>2</sub><sup>+</sup> ion is unstable in solution and will disproportionate into Pu<sup>4+</sup> and PuO<sub>2</sub><sup>2+</sup>; the Pu<sup>4+</sup> will then oxidize the remaining PuO<sub>2</sub><sup>+</sup> to PuO<sub>2</sub><sup>2+</sup>, being reduced in turn to Pu<sup>3+</sup>. Thus, aqueous solutions of plutonium tend over time towards a mixture of Pu<sup>3+</sup> and PuO<sub>2</sub><sup>2+</sup>.
:{{cite web
 | title = Nuclear Criticality Safety Engineering Training Module 10 – Criticality Safety in Material Processing Operations, Part 1
 | url = http://ncsp.llnl.gov/ncset/Module10.pdf
 | format = PDF
 | accessdate = 2006-02-15
 | year = 2002
 | last = Crooks
 | first = William J.
}}</ref>
* Pu(VI), as PuO<sub>2</sub><sup>2+</sup> (pink orange)
* Pu(VII), as PuO<sub>5</sub><sup>3−</sup> (green)–the heptavalent ion is rare

The color shown by plutonium solutions depends on both the oxidation state and the nature of the acid [[anion]].<ref>
{{cite book
 | last = Matlack
 | first = George
 | title = A Plutonium Primer: An Introduction to Plutonium Chemistry and its Radioactivity
 | publisher = Los Alamos National Laboratory
 | year = 2002
 | id = LA-UR-02-6594
}}</ref> It is the acid anion that influences the degree of [[complex (chemistry)|complexing]]—how atoms connect to a central atom—of the plutonium species.

Metallic plutonium is produced by reacting plutonium(IV) fluoride with [[barium]], [[calcium]] or [[lithium]] at 1200&nbsp;°C.<ref>
{{cite book
 | title = Concise Encyclopedia Chemistry
 | last = Eagleson
 | first = Mary
 | publisher = Walter de Gruyter
 | isbn = 9783110114515
 | page = 840
 | year = 1994
}}</ref> It is attacked by [[acid]]s, [[oxygen]], and steam but not by [[alkalis]] and dissolves easily in concentrated [[hydrochloric acid|hydrochloric]], [[hydroiodic acid|hydroiodic]] and [[perchloric acid]]s.<ref name = "Miner1968p545">{{harvnb|Miner|1968|p = 545}}</ref> Molten metal must be kept in a vacuum or an inert atmosphere to avoid reaction with air.<ref name = "Miner1968p542">{{harvnb|Miner|1968|p = 542}}</ref> At 135&nbsp;°C the metal will ignite in air and will explode if placed in [[carbon tetrachloride]].<ref name = "Emsley2001"/>

[[Image:Plutonium pyrophoricity.jpg|thumb|left|Plutonium [[pyrophoricity]] can cause it to look like a glowing ember under certain conditions.]]
Plutonium is a reactive metal. In moist air or moist [[argon]], the metal oxidizes rapidly, producing a mixture of [[oxide]]s and [[hydride]]s.<ref name = "WISER">
{{cite web
 | url = http://webwiser.nlm.nih.gov/getSubstanceData.do;jsessionid=89B673C34252C77B4C276F2B2D0E4260?substanceID=419&displaySubstanceName=Plutonium,%20Radioactive&UNNAID=&STCCID=&selectedDataMenuItemID=44
 | author = NIH contributors
 | publisher = U.S. National Library of Medicine, National Institutes of Health
 | location = Bethesda, (MD)
 | title = Plutonium
 | work = Wireless Information System for Emergency Responders (WISER)
 | accessdate = 2008-11-23
}} (public domain text)</ref> If the metal is exposed long enough to a limited amount of water vapor, a powdery surface coating of [[Plutonium(IV) oxide|PuO<sub>2</sub>]] is formed.<ref name = "WISER"/> Also formed is [[plutonium hydride]] but an excess of water vapor forms only PuO<sub>2</sub>.<ref name = "Miner1968p545"/>

With this coating, the metal is [[Pyrophoricity|pyrophoric]], meaning it can ignite spontaneously, so plutonium metal is usually handled in an inert, dry atmosphere of nitrogen or argon.<ref name = "WISER"/> Oxygen retards the effects of moisture and acts as a [[Passivation|passivating]] agent.<ref name = "WISER"/>

Plutonium reacts readily with oxygen, forming PuO and PuO<sub>2</sub> as well as intermediate oxides;<ref name = "CRC2006p4-27"/> plutonium oxide fills 40% more volume than plutonium metal.<ref name = "Emsley2001"/> It reacts with the [[halogen]]s, giving rise to compounds such as PuX<sub>3</sub> where X can be [[Plutonium(III) fluoride|F]], [[Plutonium(III) chloride|Cl]], Br or I; [[Plutonium tetrafluoride|PuF<sub>4</sub>]] is also seen.<ref name = "CRC2006p4-27"/> The following oxyhalides are observed: PuOCl, PuOBr and PuOI.<ref name = "CRC2006p4-27"/> It will react with carbon to form PuC, nitrogen to form PuN and [[silicon]] to form PuSi<sub>2</sub>.<ref name = "CRC2006p4-27"/>

[[Crucible]]s used to contain plutonium need to be able to withstand its strongly [[Redox|reducing]] properties.<ref name = "Miner1968p542"/> [[Refractory metals]] such as [[tantalum]] and [[tungsten]] along with the more stable oxides, [[boride]]s, [[carbide]]s, [[nitride]]s and [[silicide]]s can tolerate this.<ref name = "Miner1968p542"/> Melting in an [[electric arc furnace]] can be used to produce small ingots of the metal without the need for a crucible.<ref name = "Miner1968p542"/>

Plutonium can form [[alloy]]s and intermediate compounds with most other metals. Exceptions include [[lithium]], [[sodium]], [[potassium]], and [[rubidium]] of the [[alkali metal]]s; and [[magnesium]], [[calcium]], [[strontium]], and [[barium]] of the [[alkaline earth metal]]s; and [[europium]] and [[ytterbium]] of the [[rare earth metal]]s.<ref name = "Miner1968p545"/> Partial exceptions include the refractory metals [[chromium]], [[molybdenum]], [[niobium]], [[tantalum]], and [[tungsten]], which are soluble in liquid plutonium, but insoluble or only slightly soluble in solid plutonium.<ref name = "Miner1968p545"/>

=== Occurrence ===
Trace amounts of two plutonium isotopes (Pu-239 and Pu-244) can be found in nature.  Small traces of Pu-239, a few [[parts per notation|parts per trillion]], and its [[decay product]]s are naturally found in some concentrated ores of uranium,<ref name = "Miner1968p541"/> such as the [[natural nuclear fission reactor]] in [[Oklo]], [[Gabon]].<ref>
{{cite web
 | url = http://www.ocrwm.doe.gov/factsheets/doeymp0010.shtml
 | title = Oklo: Natural Nuclear Reactors
 | publisher = U.S. Department of Energy, Office of Civilian Radioactive Waste Management
 | year = 2004
 | id = DOE/YMP-0010
 | author = DOE contributors
 | accessdate = 2008-11-16
}}</ref> The ratio of Pu-239 to U at the [[Cigar Lake Mine]] uranium deposit ranges from {{nowrap|2.4 &times; 10<sup>−12</sup>}} to {{nowrap|44 &times; 10<sup>−12</sup>}}.<ref name = "Cigar">
{{cite journal
 | journal = Geochimica et Cosmochimica Acta
 | volume = 63 | issue = 2 | pages = 275–285
 | year = 1999
 | doi = 10.1016/S0016-7037(98)00282-8
 | title = Nature's uncommon elements: plutonium and technetium
 | first = David
 | last = Curtis
 | coauthors = Fabryka-Martin, June; Paul, Dixon; Cramer, Jan
}}</ref> Even smaller amounts of [[primordial nuclide|primordial]] Pu-244 occur naturally due to its relatively long half-life of about 80 million years.<ref>
{{cite journal
 | first = D. C.
 | last = Hoffman
 | coauthors = Lawrence, F. O.; Mewherter, J. L.; and Rourke, F. M.
 | title = Detection of Plutonium-244 in Nature
 | journal = Nature
 | id = Nr. 34
 | year = 1971
 | pages = 132–134
 | doi = 10.1038/234132a0
 | volume = 234
}}</ref>

Minute traces are found in the human body due to the 550 above-ground [[nuclear testing|nuclear tests]] which have been performed and several major [[nuclear accident]]s.<ref name = "Emsley2001">{{harvnb|Emsley|2001}}</ref> Most atmospheric nuclear testing was stopped in 1963 by the [[Limited Test Ban Treaty]] but France continued to test into the 1980s and several other nations also conducted tests after 1963. Because it is specifically manufactured and is the result of radioactive decay of uranium ores, Pu-239 is the most abundant isotope of plutonium.<ref name = "Emsley2001"/>

== History ==
=== Discovery ===
[[Enrico Fermi]] and a team of scientists at the [[University of Rome La Sapienza|University of Rome]] reported that they had discovered element 94 in 1934.<ref>{{cite web
 | url = http://www.nndc.bnl.gov/content/evaluation.html
 | title = A Short History of Nuclear Data and Its Evaluation
 | last = Holden | first = Norman E.
 | publisher = National Nuclear Data Center, Brookhaven National Laboratory
 | location = Upton (NY)
 | work = 51st Meeting of the USDOE Cross Section Evaluation Working Group
 | year = 2001
 | accessdate = 2009-01-03
 }}</ref> Fermi called the element ''[[hesperium]]'' and mentioned it in his Nobel Lecture in 1938.<ref>{{cite web
 | url = http://www.nobel.se/physics/laureates/1938/fermi-lecture.pdf
 | format = PDF
 | last = Fermi | first = Enrico
 | date = December 12, 1938
 | title = Artificial radioactivity produced by neutron bombardment: Nobel Lecture
 | publisher = Royal Swedish Academy of Sciences
 }}</ref> However, the sample was actually a mixture of [[barium]], [[krypton]], and other elements, but this was not known at the time because [[nuclear fission]] had not been discovered yet.<ref>{{cite web
 | url = http://www.philosophy.umd.edu/Faculty/LDarden/sciinq/
 | title = The Nature of Scientific Inquiry
 | last = Darden | first = Lindley
 | chapter = Enrico Fermi: "Transuranium" Elements, Slow Neutrons
 | publisher = Department of Philosophy, University of Maryland
 | year = 1998
 | accessdate = 2008-01-03
 | location = College Park (MD)
 }}</ref>

[[Image:Glenn Seaborg 1964.png|thumb|[[Glenn T. Seaborg]] and his team at Berkeley were the first to produce plutonium.]]
Plutonium (specifically, Pu-238) was first produced and isolated on December 14, 1940, and chemically identified on February 23, 1941, by Dr. [[Glenn T. Seaborg]], [[Edwin McMillan|Edwin M. McMillan]], [[Joseph W. Kennedy|J. W. Kennedy]], [[Zachary M. Tatom|Z. M. Tatom]], and [[Arthur Wahl|A. C. Wahl]] by [[deuteron]] bombardment of uranium in the {{convert|60|in|cm|sing = on}} [[cyclotron]] at the [[University of California, Berkeley]].<ref name = 'ACS'>
{{cite web
 | url = http://acs.lbl.gov/Seaborg.talks/65th-anniv/14.html
 | title = Elements 93 and 94
 | accessdate = 2008-09-17
 | author = LBNL contributors
 | publisher = Advanced Computing for Science Department, Lawrence Berkeley National Laboratory
}}</ref> In the 1940 experiment, [[neptunium]]-238 was created directly by the bombardment but decayed by [[beta emission]] two days later, which indicated the formation of element 94.<ref name = "Emsley2001"/>

A paper documenting the discovery was prepared by the team and sent to the journal ''[[Physical Review]]'' in March 1941.<ref name = "Emsley2001"/> The paper was withdrawn before publication after the discovery that an isotope of the new element (Pu-239) could undergo nuclear fission in a way that might be useful in an [[atomic bomb]]. Publication was delayed until a year after the end of [[World War II]] due to security concerns.<ref name = "Stwertka1998">{{harvnb|Stwertka|1998}}</ref>

Edwin McMillan had recently named the first transuranium element after the planet [[Neptune]] and suggested that element&nbsp;94, being the next element in the series, be named for what was then considered the next planet, [[Pluto]].<ref name = "Heiserman1992">{{harvnb|Heiserman|1992}}</ref>{{inote|page 338}}<ref group = "note">This was not the first time somebody suggested that an element be named "plutonium." A decade after barium was discovered, a Cambridge University professor suggested it be renamed to "plutonium" because the element was not (as suggested by the [[Greek language|Greek]] root, ''barys'', it was named for) heavy. He reasoned that, since it was produced by the relatively new technique of [[electrolysis]], its name should refer to [[fire]]. Thus he suggested it be named for the Roman god of the underworld, [[Pluto (god)|Pluto]]. {{harv|Heiserman|1992}}{{inote|page 338}}</ref> Seaborg originally considered the name "plutium", but later thought that it did not sound as good as "plutonium."<ref name="Clark57">
{{cite journal
 | last = Clark
 | first = David L.
 | coauthors = Hobart, David E.
 | title = Reflections on the Legacy of a Legend: Glenn T. Seaborg, 1912–1999
 | journal = Los Alamos Science
 | volume = 26
 | year = 2000
 | pages = 56–61, on 57
 | url = http://www.fas.org/sgp/othergov/doe/lanl/pubs/00818011.pdf
 | format = PDF
 | accessdate = 2009-02-15
}}</ref> He chose the letters "Pu" as a joke, which passed without notice into the periodic table.<ref group = "note">As one article puts it, referring to information Seaborg gave in a talk: "The obvious choice for the symbol would have been Pl, but facetiously, Seaborg suggested Pu, like the words a child would exclaim, 'Pee-yoo!' when smelling something bad. Seaborg thought that he would receive a great deal of flak over that suggestion, but the naming committee accepted the symbol without a word."
:{{cite journal
 | first = David L.
 | last = Clark
 | coauthors = Hobart, David E.
 | title = Reflections on the Legacy of a Legend: Glenn T. Seaborg, 1912–1999
 | journal = Los Alamos Science
 | volume = 26
 | pages = 56–61, on 57
 | year = 2000
 | url = http://www.fas.org/sgp/othergov/doe/lanl/pubs/00818011.pdf
 | format = PDF
 | accessdate = 2009-02-15
}}</ref> Alternate names considered by Seaborg and others were "ultimium" or "extremium" because of the now-discredited belief that they had found the last possible [[chemical element|element]] on the [[periodic table]].<ref>
{{cite web
 | url = http://www.pbs.org/wgbh/pages/frontline/shows/reaction/interviews/seaborg.html
 | title = Frontline interview with Seaborg
 | publisher = Public Broadcasting Service
 | author = PBS contributors
 | work = Frontline
 | year = 1997
 | accessdate = 2008-12-07
}}</ref>

=== Early research ===
The basic chemistry of plutonium was found to resemble uranium after a few months of initial study.<ref name = "Emsley2001"/> Early research was continued at the secret [[Metallurgical Laboratory]] of the [[University of Chicago]]. On August 18, 1942, a trace quantity of this element was isolated and measured for the first time. About 50&nbsp;micrograms of plutonium-239 combined with uranium and fission products was produced and only about 1&nbsp;microgram was isolated.<ref name = "Miner1968p541">{{harvnb|Miner|1968|p = 541}}</ref> This procedure enabled chemists to determine the new element's atomic weight.<ref name = "uchicago">
{{cite web
 | title = Room 405, George Herbert Jones Laboratory
 | publisher = National Park Service
 | url = http://tps.cr.nps.gov/nhl/detail.cfm?ResourceId=735&ResourceType=Building
 | accessdate = 2008-12-14
 | author = NPS contributors
}}</ref><ref group = "note">Room 405 of the [[George Herbert Jones Laboratory]], where the first isolation of plutonium took place, was named a [[National Historic Landmark]] in May 1967.</ref>

In November 1943 some plutonium trifluoride was reduced to create the first sample of plutonium metal: a few micrograms of metallic beads.<ref name = "Miner1968p541"/> Enough plutonium was produced to make it the first synthetically made element to be visible with the unaided eye.<ref name = "Miner1968p540">{{harvnb|Miner|1968|p = 540}}</ref>

The nuclear properties of plutonium-239 were also studied; researchers found that when it is hit by a neutron it breaks apart (fissions) by releasing more neutrons and energy. These neutrons can hit other atoms of plutonium-239 and so on in an exponentially fast [[Nuclear chain reaction|chain reaction]]. This can result in an explosion large enough to destroy a city if enough of the isotope is concentrated to form a critical mass.<ref name = "Emsley2001"/>

=== Production during the Manhattan Project ===
During World War II the U.S. government established the [[Manhattan Project]], which was tasked with developing an atomic bomb. The three primary research and production sites of the project were the plutonium production facility at what is now the [[Hanford Site]], the [[uranium enrichment]] facilities at [[Oak Ridge, Tennessee]], and the weapons research and design laboratory, now known as [[Los Alamos National Laboratory]].<ref>
{{cite web
 | url = http://www.lanl.gov/history/road/siteselection.shtml
 | author = LANL contributors
 | work = LANL History
 | title = Site Selection
 | publisher = Los Alamos National Laboratory
 | location = Los Alamos, New Mexico
 | accessdate = 2008-12-23
 }}</ref>

[[File:B-Reactor Hanford.jpg|left|thumb|The Hanford [[B Reactor]] face under construction—the first plutonium-production reactor]]

The first production reactor that made plutonium-239 was the [[X-10 Graphite Reactor]]. It went online in 1943 and was built at a facility in Oak Ridge that later became the [[Oak Ridge National Laboratory]].<ref name = "Emsley2001"/><ref group = "note">During the Manhattan Project, plutonium was also often referred to as simply "49": the number 4 was for the last digit in 94 (atomic number of plutonium), and 9 was for the last digit in Pu-239, the weapon-grade fissile isotope used in nuclear bombs.
:{{Cite journal
 | last = Hammel
 | first = E.F.
 | year = 2000
 | title = The taming of "49"&nbsp; – Big Science in little time. Recollections of Edward F. Hammel, pp. 2-9. In: Cooper N.G. Ed. (2000). Challenges in Plutonium Science
 | journal = Los Alamos Science
 | volume = 26
 | issue = 1
 | pages = 2–9
 | url = http://www.fas.org/sgp/othergov/doe/lanl/pubs/00818010.pdf
 | accessdate = 2009-02-15
}}
:{{Cite journal
 | last = Hecker
 | first = S.S.
 | year = 2000
 | title = Plutonium: an historical overview. In: Challenges in Plutonium Science
 | journal = Los Alamos Science
 | volume = 26
 | issue = 1
 | pages = 1–2
 | url = http://www.fas.org/sgp/othergov/doe/lanl/pubs/number26.htm
 | accessdate = 2009-02-15
}}</ref>

On April 5, 1944, [[Emilio Segrè]] at Los Alamos received the first sample of reactor-produced plutonium from Oak Ridge.<ref name="AtomicTimeline">
{{cite web
 | url = http://www.atomicheritage.org/index.php?option=com_content&task=view&id=288&Itemid=202
 | title = Atomic History Timeline 1942-1944
 | publisher = Atomic Heritage Foundation
 | last = Sublette
 | first = Carey
 | location = Washington (DC)
 | accessdate = 2008-12-22
 }}</ref>  Within ten days, he discovered that reactor-bred plutonium had a higher concentration of the isotope Pu-240 than cyclotron-produced plutonium. Pu-240 has a high [[spontaneous fission]] rate, raising the overall background neutron level of the plutonium sample. The original [[Gun-type fission weapon|gun-type]] plutonium weapon, code-named "[[Thin Man nuclear bomb|Thin Man]]", had to be abandoned as a result—the increased number of spontaneous neutrons meant that nuclear pre-detonation (a [[Fizzle (nuclear test)|fizzle]]) would be likely.

The entire plutonium weapon design effort at Los Alamos was soon changed to the more complicated implosion device, code-named "[[Fat Man]]." With an implosion weapon, a solid sphere of plutonium is compressed to a high density with explosive lenses—a technically more daunting task than the simple gun-type design, but necessary in order to use plutonium for weapons purposes. ([[Enriched uranium]], by contrast, can be used with either method.)<ref name="AtomicTimeline"/>

Construction of the Hanford [[B Reactor]], the first industrial-sized nuclear reactor for the purposes of material production, was completed in March 1945.<ref name=100B>
{{cite book
 | title = History of 100-B Area
 | publisher = Westinghouse Hanford Company
 | location = Richland, Washington
 | id = WHC-EP-0273
 | last = Wahlen
 | first = R.K.
 | year = 1989
 | pages = iv, 1
 | url = http://www.hanford.gov/doe/history/files/HistoryofBArea.pdf
 | format = PDF
 | accessdate = 2009-02-15
}}</ref> B Reactor produced the fissile material for the plutonium weapons used during World War II.<ref group=note>The American Society of Mechanical Engineers (ASME) established B Reactor as a National Historic Mechanical Engineering Landmark in September 1976.
:{{cite book
 | title = History of 100-B Area
 | publisher = Westinghouse Hanford Company
 | location = Richland, Washington
 | id = WHC-EP-0273
 | last = Wahlen
 | first = R.K.
 | year = 1989
 | page = 1
 | url = http://www.hanford.gov/doe/history/files/HistoryofBArea.pdf
 | format = PDF
 | accessdate = 2009-02-15
}}
In August 2008, B Reactor was designated a U.S. [[National Historic Landmark]].
:{{cite web|url=http://www.nps.gov/history/nr/listings/20080829.HTM |title=Weekly List Actions |accessdate=2008-08-30|work= |author= |publisher= National Park Service |date=2008-08-29 |quote=}}
</ref> B, D and F were the initial reactors built at Hanford, and six additional plutonium-producing reactors were built later at the site.<ref name=100B/>

In 2004, a [[safe]] was discovered during excavations of a burial trench at the [[Hanford nuclear site]]. Inside the safe were various items, including a large glass bottle containing a whitish slurry which was subsequently identified as the oldest sample of weapons-grade plutonium known to exist. Isotope analysis by [[Pacific Northwest National Laboratory]] indicated that the plutonium in the bottle was manufactured in the X-10 reactor at Oak Ridge during 1944.
<ref>
{{Cite web
| last = Rincon
| first = Paul
| year = 2009
| title = BBC NEWS – Science & Environment – US nuclear relic found in bottle
| url = http://news.bbc.co.uk/2/hi/science/nature/7918618.stm
| accessdate = 2009-03-02
}}
</ref>
<ref>
{{Cite journal
| last = Gebel
| first = Erika
| year = 2009
| title = Old plutonium, new tricks
| journal = Analytical Chemistry
| volume = 81
| issue = 5
| pages = 1724
| doi = 10.1021/ac900093b
| url = http://pubs.acs.org/doi/abs/10.1021/ac900093b
| accessdate = 2009-03-02
}}
</ref>
<ref>
{{Cite journal
| last = Schwantes
| first = Jon M.
| coauthors = Matthew Douglas, Steven E. Bonde, James D. Briggs, Orville T. Farmer, Lawrence R. Greenwood, Elwood A. Lepel, Christopher R. Orton, John F. Wacker, Andrzej T. Luksic
| year = 2009
| title = Nuclear archeology in a bottle: Evidence of pre-Trinity U.S. weapons activities from a waste burial site
| journal = Analytical Chemistry
| volume = 81
| issue = 4
| pages = 1297-1306
| doi = 10.1021/ac802286a
| url = http://dx.doi.org/10.1021/ac802286a
| accessdate = 2009-03-02
}}</ref>

=== Trinity and Fat Man atomic bombs ===
[[File:Fission bomb assembly methods.svg|right|thumb|Because of the presence of Pu-240 in reactor-bred plutonium, the implosion design was developed for the "[[Fat Man]]" and ''[[Trinity test|Trinity]]" weapons]]

The first atomic bomb test, codenamed [[Trinity test|"Trinity"]] and detonated on July 16, 1945, near [[Alamogordo, New Mexico]], used plutonium as its fissile material.<ref name = "Miner1968p541"/> The implosion design of "[[the Gadget]]", as the Trinity device was code-named, used conventional explosive lenses to compress a sphere of plutonium into a supercritical mass, which was simultaneously showered with neutrons from an initiator made of [[polonium]] and [[beryllium]] ([[neutron source]]: [[Neutron_source#Small_sized_devices|(α, n) reaction]]).<ref name = "Emsley2001"/> Together, these ensured a runaway chain reaction and explosion. The overall weapon weighed over 4 tonnes, although it used just 6.2 kg of plutonium in its core.<ref>{{cite web
 | first = Carey
 | last = Sublette
 | work = Nuclear Weapons Frequently Asked Questions
 | url = http://nuclearweaponarchive.org/Nwfaq/Nfaq8.html#nfaq8.1.1
 | title = 8.1.1 The Design of Gadget, Fat Man, and "Joe 1" (RDS-1)
 | accessdate = 2008-01-04
 | date = 2007-07-03
 | edition = 2.18
 | publisher = The Nuclear Weapon Archive
 }}</ref> About 20% of the plutonium used in the Trinity weapon underwent fission, resulting in an explosion with an energy equivalent to approximately 20,000 tons of [[Trinitrotoluene|TNT]].<ref name="yield">{{cite book
 | first = John
 | last = Malik
 | url = http://www.fas.org/sgp/othergov/doe/lanl/docs1/00313791.pdf
 | title = The Yields of the Hiroshima and Nagasaki Explosions
 | publisher = Los Alamos
 | id = LA-8819
 | date = September 1985
 | page = Table VI
 | accessdate = 2009-02-15
 }}</ref><ref group="note" name="efficiency">The efficiency calculation is based on the fact that 1 kg of Pu-239 (or U-235) fissioning results in an energy release of approximately 17 [[kiloton|kt]], leading to a rounded estimate of 1.2 kg plutonium actually fissioned to produce the 20 kt yield. On the figure of 1 kg = 17 kt,
:{{cite web
 | authorlink = Richard Garwin
 | url = http://www.fas.org/rlg/PNWM_UMich.pdf
 | title = Proliferation of Nuclear Weapons and Materials to State and Non-State Actors: What It Means for the Future of Nuclear Power
 | work = University of Michigan Symposium
 | date = 2002-10-04
 | publisher = Federation of American Scientists
 | accessdate = 2009-01-04
 }}</ref>

An identical design was used in the "[[Fat Man]]" atomic bomb dropped on [[Nagasaki, Nagasaki|Nagasaki, Japan]], on August 9, 1945, killing 70,000 people and wounding another 100,000.<ref name = "Emsley2001"/> The "[[Little Boy]]" bomb dropped on [[Hiroshima]] three days earlier used [[uranium-235]], not plutonium. Japan capitulated on August 15 to General [[Douglas MacArthur]], effectively ending the war. Only after the announcement of the first atomic bombs was the existence of plutonium made public.

=== Cold War use and waste ===
Large stockpiles of weapons-grade plutonium were built up by both the [[Soviet Union]] and the [[United States]] during the [[Cold War]]. The U.S. reactors at Hanford and the [[Savannah River Site]] in South Carolina produced 103&nbsp;tonnes,<ref>
{{cite book
 | title = Historic American Engineering Record: B Reactor (105-B Building)
 | author = DOE contributors
 | publisher = U.S. Department of Energy
 | url = http://www.fas.org/sgp/othergov/doe/pu50yb.html#ZZ13
 | year = 2001
 | location = Richland (WA)
 | page = 110
 | id = DOE/RL-2001-16
 | accessdate = 2008-12-24
}}</ref> and an estimated 170&nbsp;tonnes of military-grade plutonium was produced in Russia.<ref>
{{cite conference
 | title = Safeguarding nuclear weapons-usable materials in Russia
 | url = http://docs.nrdc.org/nuclear/nuc_06129701a_185.pdf
 | first = Thomas B.
 | last = Cochran
 | conference = International Forum on Illegal Nuclear Traffic
 | publisher = Natural Resources Defense Council, Inc
 | location = Washington (DC)
 | year = 1997
 | accessdate = 2008-12-21
}}</ref><ref group = note>Much of this plutonium was used to make the fissionable cores of a type of thermonuclear weapon employing the [[Teller–Ulam design]]. These so-called 'hydrogen bombs' are a variety of nuclear weapon that use a fission bomb to trigger the [[nuclear fusion]] of heavy [[hydrogen]] isotopes. Their destructive yield is commonly in the millions of tons of TNT equivalent compared with the thousands of tons of TNT equivalent of fission-only devices.{{harv|Emsley|2001}}</ref> Each year about 20&nbsp;tonnes of the element is still produced as a by-product of the [[nuclear power]] industry.<ref name = "CRC2006p4-27">{{harvnb|CRC|2006|p = 4–27}}</ref> As much as 1000&nbsp;tonnes of plutonium may be in storage with more than 200&nbsp;tonnes of that either inside or extracted from nuclear weapons.<ref name = "Emsley2001"/>
[[SIPRI]] estimated the world plutonium stockpile in 2007 as about 500 tons, divided equally between weapon and civilian stocks, but all weapon-usable..<ref>{{cite book|title=SIPRI Yearbook 2007: Armaments, Disarmament, and International Security|author=[[Stockholm International Peace Research Institute]]|publisher=[[Oxford University Press]]|year=2007|page=567|ISBN=0199230218, 9780199230211|url=http://books.google.com/books?id=2M0C6SERFG0C&pg=PA567}}</ref>

[[Image:Yucca Mountain emplacement drifts.jpg|thumb|Proposed waste storage tunnel design for the [[Yucca Mountain nuclear waste repository]]]]
Since the end of the Cold War, these stockpiles have become a focus of [[nuclear proliferation]] concerns. In the U.S., some plutonium extracted from dismantled nuclear weapons is melted to form glass logs of plutonium oxide that weigh two&nbsp;tonnes.<ref name = "Emsley2001"/> The glass is made of [[borosilicate]]s mixed with [[cadmium]] and [[gadolinium]].<ref group = note>[[Gadolinium zirconium oxide]] ({{chem|Gd|2|Zr|2|O|7}}) has been studied because it could hold plutonium for up to 30 million years.{{harv|Emsley|2001}}</ref> These logs are planned to be encased in [[stainless steel]] and stored as much as 4&nbsp;km underground in bore holes that will be back-filled with [[concrete]].<ref name = "Emsley2001"/> As of 2008, the only facility in the U.S. that is scheduled to store plutonium in this way is the [[Yucca Mountain nuclear waste repository]], which is about {{convert|100|mi|km}} north-east of [[Las Vegas, Nevada]].<ref>{{cite web
 | url= http://georgewbush-whitehouse.archives.gov/news/releases/2002/07/20020723-2.html
 | archiveurl= http://web.archive.org/web/20080306193653/http://georgewbush-whitehouse.archives.gov/news/releases/2002/07/20020723-2.html
 | archivedate= 2008-03-06
 | title= President Signs Yucca Mountain Bill
 | publisher = The White House
 | author = Press Secretary
 | location = Washington (DC)
 | date= July 23, 2002 |work= | publisher= Office of the Press Secretary, White House
 | accessdate= 2009-01-04 }}</ref> Local and state opposition to this plan has delayed efforts to store nuclear waste at Yucca Mountain.

=== Medical experimentation ===
{{seealso|Human radiation experiments}}
During and after the end of World War II, scientists working on the Manhattan Project and other nuclear weapons research projects conducted studies of the effects of plutonium on laboratory animals and human subjects.<ref name = "Injection"/> Animal studies found that a few milligrams of plutonium per kilogram of tissue is a lethal dose.<ref name="PuHealth"/>{{inote|page 78}}

In the case of human subjects, this involved injecting solutions containing (typically) five micrograms of plutonium into hospital patients thought to be either terminally ill, or to have a life expectancy of less than ten years either due to age or chronic disease condition.<ref name = "Injection"/> This was reduced to one microgram in July 1945 after animal studies found that the way plutonium distributed itself in bones was more dangerous than [[radium]].<ref name="PuHealth">{{cite journal
 | title = Plutonium and Health: How great is the risk?
 | journal = Los Alamos Science
 | year = 2000
 | issue = 26
 | pages = 78–79
 | last = Voelz
 | first = George L.
 | location = Los Alamos (NM)
 | publisher = Los Alamos National Laboratory
 }}</ref>{{inote|pages 78-79}}

Eighteen human test subjects were injected with plutonium without [[informed consent]].<ref name = "Injection"/> The tests were used to create diagnostic tools to determine the uptake of plutonium in the body in order to develop safety standards for working with plutonium.<ref name = "Injection">
{{cite journal
 | journal = Los Alamos Science
 | title = The Human Plutonium Injection Experiments
 | url = http://library.lanl.gov/cgi-bin/getfile?00326640.pdf
 | accessdate = 2006-06-06
 | year = 1995
 | first = William
 | last = Moss
 | coauthors = Eckhardt, Roger
 | volume = 23
 | pages = 188, 205, 208, 214
 | format = PDF
 | publisher = Los Alamos National Laboratory
}}</ref>

The episode is now considered to be a serious breach of medical ethics and of the [[Hippocratic Oath]]. More sympathetic commentators have noted that while it was definitely a breach in trust and ethics, "the effects of the plutonium injections were not as damaging to the subjects as the early news stories painted, nor were they so inconsequential as many scientists, then and now, believe."<ref>
{{cite journal
 | last = Yesley
 | first = Michael S.
 | title = 'Ethical Harm' and the Plutonium Injection Experiments
 | journal = Los Alamos Science
 | volume = 23
 | year = 1995
 | pages = 280–283
 | url = http://www.fas.org/sgp/othergov/doe/lanl/pubs/00326649.pdf
 | format = PDF
 | accessdate = 2009-02-15
}}</ref>

== Applications ==
=== Explosives ===
[[Image:NagasakibombEdit.jpeg|thumb|150px|The [[Atomic bombings of Hiroshima and Nagasaki|atomic bomb dropped on Nagasaki, Japan]] in 1945 had a plutonium core.]]
The isotope Pu-239 is a key fissile component in [[nuclear weapon]]s, due to its ease of fission and availability. Encasing the bomb's sphere of plutonium in a [[Nuclear weapon design|tamper]] (an optional layer of dense material) decreases the amount of plutonium needed to reach [[critical mass (nuclear)|critical mass]] by [[neutron reflector|reflecting escaping neutrons]] back into the plutonium core. This reduces the amount of plutonium needed to reach criticality from 16&nbsp;kg to 10&nbsp;kg, which is a sphere with a diameter of about {{convert|10|cm|0}}.<ref>
{{cite book
 | title = Physics for Radiation Protection
 | last = Martin
 | first = James E.
 | year = 2000
 | publisher = Wiley-Interscience
 | isbn = 0471353736
 | edition = 1st
 | page = 532
}}</ref> This critical mass is about a third of that for U-235.<ref name = "Heiserman1992"/>

The "[[Fat Man]]"-type plutonium bombs produced during the [[Manhattan Project]] used explosive compression of plutonium to obtain significantly higher densities than normal, combined with a central neutron source to begin the reaction and increase efficiency. Thus only 6.2&nbsp;kg of plutonium was needed for an [[Nuclear weapon yield|explosive yield]] equivalent to 20 kilotons of [[Trinitrotoluene|TNT]].<ref name="yield"/><ref name = "FASdesign">
{{cite web
 | url = http://www.fas.org/nuke/intro/nuke/design.htm
 | title = Nuclear Weapon Design
 | publisher = Federation of American Scientists
 | year = 1998
 | accessdate = 2008-12-07
 | author = FAS contributors
}}</ref> (See also [[Nuclear weapon design]].) Hypothetically, as little as 4&nbsp;kg of plutonium—and maybe even less—could be used to make a single atomic bomb using very sophisticated assembly designs.<ref name = "FASdesign"/>

=== Use of nuclear waste ===
[[PUREX]] (''P''lutonium–''UR''anium ''EX''traction) [[Nuclear reprocessing|reprocesses]] [[spent nuclear fuel]] to extract uranium and plutonium to form a mixed oxide ([[MOX fuel|MOX]]) fuel for reuse in nuclear reactors. Weapons grade plutonium can be added to the fuel mix. MOX fuel is used in [[light water reactor]]s and consists of 60&nbsp;kg of plutonium per tonne of fuel; after four years, three-quarters of the plutonium is burned (turned into other elements).<ref name = "Emsley2001"/> [[Breeder reactor]]s are specifically designed to create more fissionable material than they consume.

MOX fuel has been in use since the 1980s and is widely used in Europe.<ref>
{{cite web
 | author = WNA contributors
 | url = http://www.world-nuclear.org/info/inf29.html
 | title = Mixed Oxide Fuel (MOX)
 | year = 2006
 | location = London (UK)
 | publisher = World Nuclear Association
 | accessdate = 2008-12-14
}}</ref> In September 2000, the United States and the [[Russian Federation]] signed a Plutonium Management and Disposition Agreement by which each agreed to dispose of 34&nbsp;tonnes of weapon grade plutonium.<ref name = USMOX>
{{cite book
 | title = Plutonium Storage at the Department of Energy's Savannah River Site: First Annual Report to Congress
 | publisher = Defense Nuclear Facilities Safety Board
 | year = 2004
 | pages = A–1
 | author = DNFSB staff
 | chaptertitle = Public Law 107-314, Subtitle E
 | url = http://www.hss.energy.gov/deprep/2004/fb04y28b.pdf
 | format = PDF
 | accessdate = 2009-02-15
}} (public domain text)</ref> The [[U.S. Department of Energy]] plans to dispose of 34&nbsp;tonnes of weapon grade plutonium in the United States before the end of 2019 by converting the plutonium to a MOX fuel to be used in commercial nuclear power reactors.<ref name = USMOX/>

Efficiencies are also attained through reprocessing: a fuel rod is reprocessed after three years of use to remove waste products, which by then account for 3% of the total weight of the rods.<ref name = "Emsley2001"/> Any uranium or plutonium isotopes produced during those three years are left and the rod goes back into production.<ref group = note>Breakdown of plutonium in a spent nuclear fuel rod: Pu-239 (~58%), Pu-240 (24%), Pu-241 (11%), Pu-242 (5%), and Pu-238 (2%). {{harv|Emsley|2001}}</ref> However, the presence of up to 1% [[gallium]] per mass in weapon grade plutonium has the potential to interfere with long-term operation of a light water reactor.<ref>
{{cite journal
 | title = Thermochemical Behavior of Gallium in Weapons-Material-Derived Mixed-Oxide Light Water Reactor (LWR) Fuel
 | first = Theodore M.
 | last = Besmann
 | journal = Journal of the American Ceramic Society
 | volume = 81
 | issue = 12
 | pages = 3071–3076
 | year = 2005
 | url =
 | doi = 10.1111/j.1151-2916.1998.tb02740.x
}}<!-- {{doi|10.1007/BF02881277}}--></ref>

<sup>241</sup>Am has recently been suggested for use as a denaturing agent in plutonium reactor fuel rods to render the fuel unusable for conversion to [[nuclear weapons]].<ref>{{cite news | title = BGU combats nuclear proliferation | url = http://www.jpost.com/servlet/Satellite?cid=1235898328437&pagename=JPost%2FJPArticle%2FShowFull| accessdate = 2009-03-05}}</ref>

=== Power and heat source ===
[[Image:Plutonium pellet.jpg|thumb|150px|A glowing pellet of <sup>238</sup>PuO<sub>2</sub>]]
The isotope [[plutonium-238]] (Pu-238) has a half-life of 87.5&nbsp;years. It emits a large amount of [[thermal energy]] with low levels of both [[gamma]] rays/particles and [[spontaneous fission|spontaneous neutron]] rays/particles.<ref name="pumper">{{cite journal
 | url = http://arq.lanl.gov/source/orgs/nmt/nmtdo/AQarchive/05spring/heart.html
 | journal = Actinide Research Quarterly
 | title = From heat sources to heart sources: Los Alamos made material for plutonium-powered pumper
 | author = ARQ contributors
 | location = Los Alamos (NM)
 | publisher = Los Alamos National Laboratory
 | issue = 1
 | year = 2005
 | accessdate = 2009-02-15
 }}</ref> Being an [[Alpha particle|alpha emitter]], it combines high energy radiation with low penetration and thereby requires minimal shielding. A sheet of paper can be used to shield against the alpha particles emitted by Pu-238 while one [[kilogram]] of the isotope can generate 22&nbsp;million&nbsp;[[kilowatt-hour]]s of heat energy.<ref name = "Heiserman1992"/>{{inote|page 338}}<ref name="pumper"/>

These characteristics make it well-suited for electrical power generation for devices which must function without direct maintenance for timescales approximating a human lifetime. It is therefore used in [[radioisotope thermoelectric generator]]s and [[radioisotope heater unit]]s such as those in the [[Cassini–Huygens|Cassini]], [[Voyager program|Voyager]] and [[New Horizons]] space probes. Earlier versions of the same technology powered the [[ALSEP]] and [[EASEP]] systems including [[seismology|seismic]] experiments on the [[Apollo 14]] Moon mission.<ref name = "Emsley2001"/>

Plutonium-238 has also been used successfully to power artificial heart [[Artificial pacemaker|pacemaker]]s, to reduce the risk of repeated surgery.<ref>
{{cite journal
 | url = http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1502062
 | title = Trends in Cardiac Pacemaker Batteries
 | author = Venkateswara Sarma Mallela; V. Ilankumaran; and N.Srinivasa Rao
 | journal = Indian Pacing Electrophysiol
 | year = 2004
 | accessdate = 2008-12-14
 | pages = 201–212
 | issue = 4
 | id = {{PMC|1502062}}
 | pmid = 16943934
 | volume = 4
 | month = Jan
 | day = 01
}}</ref><ref>[http://www.orau.org/ptp/collection/Miscellaneous/pacemaker.htm Defunct pacemakers with Pu power source]</ref> It has been largely replaced by [[lithium]]-based [[primary cell]]s, but as of 2003 there were somewhere between 50 and 100 plutonium-powered pacemakers still implanted and functioning in living patients.<ref>
{{cite web
 | url = http://www.orau.org/PTP/collection/Miscellaneous/pacemaker.htm
 | title = Plutonium Powered Pacemaker
 | location = Oak Ridge (TN)
 | publisher = Orau.org
 | year = 1974
 | author = ORAU contributors
 | accessdate = 2008-09-12
}}</ref> Pu-238 was studied as way to provide supplemental heat to [[scuba diving]].<ref>{{cite journal
 | url = http://oai.dtic.mil/oai/oai?verb=getRecord&metadataPrefix=html&identifier=AD0708680
 | title = SEALAB III - Diver's Isotopic Swimsuit-Heater System
 | last = Bayles
 | first = John J.
 | coauthors = Taylor, Douglas
 | publisher = Naval Civil Engineering Lab
 | location = Port Hueneme (CA)
 | id = AD0708680
 | year = 1970
 }}</ref> Plutonium-238 mixed with beryllium is used to generate neutrons for research purposes.<ref name = "Emsley2001"/>

== Precautions ==
{{seealso|Plutonium in the environment}}
=== Toxicity ===
Isotopes and compounds of plutonium are toxic to highly toxic due to their radioactivity. Contamination by plutonium oxide  (spontaneously oxidized plutonium) has resulted from a number of military nuclear accidents where nuclear weapons have burned.<ref name = "ATSDR">
{{cite web
 | author = ATSDR contributors
 | publisher = U.S. Department of Health and Human Services, Agency for Toxic Substances and Disease Registry (ATSDR)
 | url = http://www.atsdr.cdc.gov/toxprofiles/tp143.html
 | title = Toxicological Profile for Plutonium, Draft for Public Comment
 | year = 2007
 | accessdate = 2008-05-22 
}}</ref> However, based on chemical [[toxicity]] alone, the element is less dangerous than [[arsenic]] or [[cyanide]] and about the same as [[caffeine]].<ref> 
{{cite journal
 | first = Bernard L.
 | last = Cohen
 | journal = Nuclear Energy
 | editor = Karl Otto Ott and Bernard I. Spinrad, eds
 | location = New York (NY)
 | publisher = Plenum Press
 | year = 1985
 | pages = 355–365}}</ref><ref name = "world-nuclear">
{{cite web
 | author = WNA contributors
 | url = http://www.world-nuclear.org/info/inf15.html
 | title = Plutonium
 | year = 2008
 | location = London (UK)
 | publisher = World Nuclear Association
 | year = 2008
 | accessdate = 2008-05-22
}}</ref>

Plutonium is more dangerous when inhaled than when ingested. The risk of [[lung cancer]] increases once the total [[equivalent dose|dose equivalent]] of inhaled radiation exceeds 400 [[sievert|mSv]].<ref name="Brown">{{cite journal | last=Brown | first=SC | coauthors=Schonbeck MF, McClure D et al. | title=Lung cancer and internal lung doses among plutonium workers at the Rocky Flats Plant: a case-control study | journal=American Journal of Epidemiology | volume=160 | issue=2 | pages=163–172 | publisher=Oxford Journals | date=July 2004 | url=http://aje.oxfordjournals.org/cgi/content/full/160/2/163 | pmid=15234938 | accessdate=2009-02-15 | doi=10.1093/aje/kwh192 }}</ref> The U.S. Department of Energy estimates that the lifetime cancer risk for inhaling 5,000 plutonium particles, each about 3&nbsp;microns wide, to be 1% over the background U.S. average.<ref>
{{cite web | author=ANL staff | url=http://consolidationeis.doe.gov/PDFs/PlutoniumANLFactSheetOct2001.pdf | title=ANL human health fact sheet--plutonium | publisher=Argonne National Laboratory | year=2001 | accessdate=2007-06-16 }}</ref> It is not absorbed into the body efficiently when ingested; only 0.04% of plutonium oxide is absorbed after ingestion.<ref name = "Emsley2001"/>  When plutonium is absorbed into the body, it is excreted very slowly, with a [[biological half-life]] of 200 years.<ref>
{{cite web
 | author = DOE staff
 | title = Radiological control technical training
 | id = DOE-HDBK-1122-99
 | publisher = U.S. Department of Energy
 | url = http://hss.energy.gov/NuclearSafety/techstds/standard/hdbk1122-04/part9of9.pdf
 | archiveurl = http://web.archive.org/web/20070630190114/http://hss.energy.gov/NuclearSafety/techstds/standard/hdbk1122-04/part9of9.pdf
 | archivedate = 2007-06-30
 | accessdate = 2008-12-14
}}</ref> Plutonium has a metallic taste.<ref>
{{cite book
 | last = Welsome
 | first = Eileen
 | authorlink =
 | coauthors =
 | title = The Plutonium Files: America's Secret Medical Experiments in the Cold War
 | publisher = Random House
 | year = 2000
 | location = New York (NY)
 | url =
 | doi =
 | isbn = 0-385-31954-1
 | page = 17
}}</ref>

The [[alpha particle|alpha]] radiation plutonium emits does not penetrate the skin but can irradiate internal organs when plutonium is inhaled or ingested.<ref name = "Emsley2001"/> Particularly at risk are the [[skeleton]], where it is likely to be absorbed by the bone surface, and the [[liver]], where it collects and becomes concentrated.<ref name = "Miner1968p545"/>

Considerably larger amounts may cause acute [[radiation poisoning]] and death if ingested or inhaled; however, no human is known to have died because of inhaling or ingesting plutonium, and many people have measurable amounts of plutonium in their bodies.<ref name = "world-nuclear"/>

=== Criticality potential ===
[[Image:Partially-reflected-plutonium-sphere.jpeg|thumb|A simulated sphere of plutonium surrounded by neutron-reflecting [[tungsten carbide]] blocks in a re-enactment of Harry Daghlian's 1945 experiment]]
Toxicity issues aside, care must be taken to avoid the accumulation of amounts of plutonium which approach [[Critical mass (nuclear)|critical mass]], particularly because plutonium's critical mass is only a third of that of uranium-235.<ref name = "Heiserman1992"/> A critical mass of plutonium emits lethal amounts of neutrons and [[gamma ray]]s.<ref name = "Miner1968p546">{{harvnb|Miner|1968|p = 546}}</ref> Plutonium in solution is more likely to form a critical mass than the solid form due to [[Neutron moderator|moderation]] by the hydrogen in water.<ref name = "CRC2006p4-27"/>

[[Criticality accident]]s have occurred in the past, some of them with lethal consequences. Careless handling of [[tungsten carbide]] bricks around a 6.2&nbsp;kg plutonium sphere resulted in a fatal dose of radiation at [[Los Alamos National Laboratory|Los Alamos]] on August 21, 1945, when scientist [[Harry K. Daghlian, Jr.]] received a dose estimated to be 5.1&nbsp;[[Sievert]] (510&nbsp;[[Roentgen equivalent man|rems]]) and died 28&nbsp;days later.<ref>
{{cite book
 | url = http://www.lanl.gov/news/index.php/fuseaction/home.story/story_id/1054/view/print
 | title = Criticality accidents report issued
 | publisher = Los Alamos National Laboratory
 | location = Los Alamos (NM)
 | accessdate = 2008-11-16
 | year = 2000
 | last = Roark | first = Kevin N.
}}</ref> Nine months later, another Los Alamos scientist, [[Louis Slotin]], died from a similar accident involving a beryllium reflector and the same plutonium core (the so-called "[[demon core]]") that had previously claimed the life of Daghlian.<ref>
{{cite web
 | url = http://www.lanl.gov/history/people/R_Schreiber.shtml
 | title = Raemer Schreiber
 | work = Staff Biographies
 | publisher = Los Alamos National Laboratory
 | location = Los Alamos (NM)
 | author = LANL contributors
 | accessdate = 2008-11-16
}}</ref> These incidents were fictionalized in the 1989 film ''[[Fat Man and Little Boy]]''.

In December 1958, during a process of purifying plutonium at Los Alamos, a critical mass was formed in a mixing vessel, which resulted in the death of a crane operator.<ref name = "CriticalityAccidents">
{{cite journal
 | title = A Review of Criticality Accidents
 | id = LA-13638
 | publisher = Los Alamos National Laboratory
 | location = Los Alamos (NM)
 | year = 2000
 | page = 16
 | last = McLaughlin
 | first = Thomas P.
 | coauthors = Monahan, Shean P.; Pruvost, Norman L.
}}</ref> Other [[nuclear and radiation accidents|nuclear accidents]] have occurred in the [[Soviet Union]], [[Japan]], and many other countries.<ref name = "CriticalityAccidents"/>

=== Flammability ===
Metallic plutonium is a fire hazard, especially if the material is finely divided.<ref name = "NucSafety">
{{cite web|url = http://www.hss.energy.gov/nuclearsafety/ns/techstds/standard/hdbk1081/hbk1081d.html#ZZ281|title = Plutonium|author = DOE contributors|work = Nuclear Safety and the Environment|publisher = Department of Energy, Office of Health Safety and Security|accessdate = 2008-12-07}}</ref> In a moist environment, plutonium forms hydrides on its surface, which are [[pyrophoricity|pyrophoric]] and may ignite in air at room temperature.<ref name = "NucSafety"/> Plutonium expands up to 70% in volume as it oxidizes and thus may break its container.<ref name = "NucSafety"/> The radioactivity of the burning material is an additional hazard. [[Magnesium oxide]] sand is probably the most effective material for extinguishing a plutonium fire.<ref name = "NucSafety"/> It cools the burning material, acting as a [[heat sink]], and also blocks off oxygen. Special precautions are necessary to store or handle plutonium in any form; generally a dry [[inert gas]] atmosphere is required.<ref>{{cite web|url = http://www.hss.energy.gov/NuclearSafety/techstds/standard/hdbk1081/hbk1081d.html#ZZ281|archiveurl = http://web.archive.org/web/20070428220410/http://www.hss.energy.gov/NuclearSafety/techstds/standard/hdbk1081/hbk1081d.html#ZZ281|archivedate = 2007-04-28|title = Primer on Spontaneous Heating and Pyrophoricity – Pyrophoric Metals – Plutonium|author = DOE contributors|publisher = U.S. Department of Energy, Office of Nuclear Safety, Quality Assurance and Environment|id = DOE-HDBK-1081-94|year = 1994|location = Washington (DC)}}</ref><ref group=note>There was a major plutonium-initiated fire at the [[Rocky Flats Plant]] near [[Boulder, Colorado|Boulder]], [[Colorado]] in 1969.
:{{cite web|first = David|last = Albright|coauthors = O'Neill, Kevin|year = 1999|url = http://www.isis-online.org/publications/usfacilities/Rfpbrf.html|title = The Lessons of Nuclear Secrecy at Rocky Flats|work = ISIS Issue Brief|accessdate = 2008-12-07|publisher = Institute for Science and International Security (ISIS)}}</ref>

== See also ==
{{portal|Chemistry|Nuvola apps edu science.svg}}
{{portal|Nuclear technology|Radioactive.svg}}
{{portal|Physics|Stylised Lithium Atom.svg}}
* [[Nuclear engineering]]
* [[Nuclear fuel cycle]]
* [[Nuclear physics]]

== Notes ==
{{reflist|group=note}}

== References ==
{{reflist|2}}

== Bibliography ==
<!-- Only list books (hence section title) used as references here -->
* <!-- CRC -->{{cite book
 | author = CRC contributors
 | title = Handbook of Chemistry and Physics
 | editor = David R. Lide
 | edition = 87th
 | year = 2006
 | publisher = CRC Press, Taylor & Francis Group
 | location = Boca Raton (FL)
 | isbn = 0849304873
 | ref = CITEREFCRC2006}}
* <!-- Em -->{{cite book
 | title = Nature's Building Blocks: An A-Z Guide to the Elements
 | last = Emsley
 | first = John
 | publisher = Oxford University Press
 | year = 2001
 | location = Oxford (UK)
 | isbn = 0198503407
 | chapter = Plutonium
 | pages = 324–329
 | ref = CITEREFEmsley2001}}
* <!-- Gr -->{{cite book
 | last = Greenwood
 | first = N. N.
 | coauthors = Earnshaw, A.
 | title = Chemistry of the Elements
 | edition = 2nd
 | publisher = Butterworth-Heinemann
 | location = Oxford (UK)
 | year = 1997
 | isbn = 0-7506-3365-4
 | page =
 | chapter =
 | ref = CITEREFGreenwood1997}}
* <!-- He -->{{cite book
 | last = Heiserman
 | first = David L.
 | title = Exploring Chemical Elements and their Compounds
 | location = New York (NY)
 | year = 1992
 | publisher = TAB Books
 | isbn = 0-8306-3018-X
 | chapter = Element 94: Plutonium
 | pages = 337–340
 | ref = CITEREFHeiserman1992
}}
* <!-- M -->{{cite book
 | title = The Encyclopedia of the Chemical Elements
 | publisher = Reinhold Book Corporation
 | location = New York (NY)
 | year = 1968
 | editor = Clifford A. Hampel (editor)
 | id = LCCN 68-29938
 | last = Miner
 | first = William N.
 | coauthors = Schonfeld, Fred W.
 | chapter = Plutonium
 | pages = 540–546
 | ref = CITEREFMiner1968
}}
* <!-- Sw -->{{cite book
 | title = Guide to the Elements
 | edition = Revised
 | first = Albert
 | last = Stwertka
 | publisher = Oxford University Press
 | year = 1998
 | chapter = Plutonium
 | pages =
 | isbn = 0-19-508083-1
 | location = Oxford (UK)
 | ref = CITEREFStwertka1998
}}

== External links ==
{{Commons|Plutonium}}
{{wiktionary|plutonium}}
{{Spoken Wikipedia|Plutonium.ogg|2009-07-18}}
*{{cite web
 | url = http://www.llnl.gov/csts/publications/sutcliffe/
 | archiveurl = http://web.archive.org/web/20060929015050/http://www.llnl.gov/csts/publications/sutcliffe/
 | archivedate = 2006-09-29
 | title = A Perspective on the Dangers of Plutonium
 | first = W.G.
 | last = Sutcliffe
 | coauthors = et al.
 | publisher = [[Lawrence Livermore National Laboratory]]
 | year = 1995
}}
*{{cite web| url = http://www.globalsecurity.org/wmd/library/report/crs/97-564.htm
 | title = Nuclear Weapons: Disposal Options for Surplus Weapons-Usable Plutonium
 | first = C.M.
 | last = Johnson
 | coauthors = Davis, Z.S.
 | work = CRS Report for Congress # 97-564 ENR
 | year = 1997
 | accessdate = 2009-02-15
}}
*{{cite web
 | url = http://www.ieer.org/fctsheet/pu-props.html
 | title = Physical, Nuclear, and Chemical, Properties of Plutonium
 | author = IEER contributors
 | publisher = [[IEER]]
 | year = 2005
 | accessdate = 2009-02-15
}}
<!-- Dead link
*{{cite web
 | url = http://consolidationeis.doe.gov/PDFs/PlutoniumANLFactSheetOct2001.pdf
 | title = DOE Plutonium fact sheet
 | author = DOE contributors
 | publisher = 
 | year = 
}}
-->
*{{cite journal
 | url = http://discovermagazine.com/2005/nov/end-of-plutonium
 | title = End of the Plutonium Age
 | last = Samuels
 | first = D.
 | journal = Discover Magazine
 | volume = 26 | issue = 11
 | year = 2005
}}
*{{cite web| url = http://www.fas.org/nuke/intro/nuke/plutonium.htm
 | title = Plutonium production
 | publisher = [[Federation of American Scientists]]
 | first = J.
 | last = Pike
 | coathors = Sherman, R.
 | year = 2000
 | accessdate = 2009-02-15
}}
*{{cite web
 | url = http://nuclearweaponarchive.org/Library/Plutonium/
 | title =  Plutonium Manufacture and Fabrication
 | publisher = Nuclearweaponarchive.org
 | author = Nuclear Weapon Archive contributors
}}
*{{cite web
 | url = http://www.nuclearfiles.org/menu/key-issues/nuclear-energy/issues/world-plutonium-inventories-ong.htm
 | title = World Plutonium Inventories
 | publisher = Nuclear Files.org
 | first = C.
 | last = Ong
 | year = 1999
 | accessdate = 2009-02-15
}}
*{{cite journal
 | url = http://www.fas.org/sgp/othergov/doe/lanl/pubs/number26.htm
 | title = Challenges in Plutonium Science
 | journal = Los Alamos Science
 | volume = I & II | issue = 26
 | author = LANL contributors
 | year = 2000
 | accessdate = 2009-02-15
}}
*{{cite web
 | url = http://toxnet.nlm.nih.gov/cgi-bin/sis/search/r?dbs+hsdb:@term+@na+@rel+plutonium,+radioactive
 | title = Plutonium, Radioactive
 | publisher = NLM Hazardous Substances Databank
 | year = 
 | author= NLM contributors
 | accessdate= 2009-02-15
}}
*{{cite web
 | url = http://alsos.wlu.edu/qsearch.aspx?browse=science/Plutonium
 | title =  Annotated Bibliography on plutonium
 | publisher = Alsos Digital Library for Nuclear Issues
 | year = 
 | author = Alsos contributors
 | accessdate = 2009-02-15
}}

{{Nuclear Technology}}
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{{featured article}}

[[Category:Actinides]]
[[Category:Carcinogens]]
[[Category:Chemical elements]]
[[Category:Nuclear materials]]
[[Category:Plutonium|*]]
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