View source for Americium-241

{{Short description|Radioactive isotope of Americium}}
{{Infobox isotope
 | symbol =Am
 | mass_number =241
 | mass = {{val|241.0568273|(12)}}<ref name="NUBASE2020">{{NUBASE2020}}</ref>
 | num_neutrons =146
 | num_protons = 95
 | abundance = 0 ([[synthetic element|synthetic]])
 | halflife ={{val|432.6|0.6|u=years}}<ref name="NUBASE2020"/>
 | image = Americium button hd.jpg
 | image_caption = Small button containing {{sup|241}}AmO{{sub|2}} from a smoke alarm
 | decay_product =Neptunium-237
 | decay_symbol =Np
 | decay_mass =237
 | decay_mode1 =[[alpha decay|α-decay]] (alpha)
 | decay_energy1 =5.486
 | decay_mode2 =[[gamma ray|γ-emission]] (gamma)
 | decay_energy2 =  0.0595409
 | decay_mode3 =CD ([[cluster decay]])
 | decay_energy3 =  93.923
 | decay_mode4 =SF ([[spontaneous fission]])
 | parent =Plutonium-241
 | parent_symbol =Pu
 | parent_mass =241
 | parent_decay =beta
 | parent2 =Curium-241
 | parent2_symbol =Cm
 | parent2_mass =241
 | parent2_decay =EC
 | parent3 =Berkelium-245
 | parent3_symbol =Bk
 | parent3_mass =245
 | parent3_decay =alpha
 | spin = 5/2−
 | excess_energy = {{val|52934.3|1.1}}<ref name="NUBASE2020"/>
 | binding_energy = {{val|7543.2795|(46)}}<ref name="NUBASE2020"/>
}}

'''Americium-241''' ('''{{sup|241}}Am''', '''Am-241''') is an [[isotope of americium]]. Like all isotopes of americium, it is [[radioactive]], with a [[half-life]] of {{val|432.2|u=years}}. {{sup|241}}Am is the most common [[isotope]] of [[americium]] as well as the most prevalent isotope of americium in [[nuclear waste]]. It is commonly found in ionization type [[smoke detector]]s and is a potential fuel for long-lifetime [[radioisotope thermoelectric generators]] (RTGs). Its common parent nuclides are [[beta decay|β{{sup|−}}]] from {{sup|241}}Pu, [[electron capture|EC]] from {{sup|241}}Cm, and [[alpha decay|α]] from {{sup|245}}Bk. {{sup|241}}Am is not [[fissile]], but is [[fissionable]], and the [[critical mass]] of a bare sphere is {{convert|57.6|–|75.6|kg|sigfig=4}} and a sphere diameter of {{convert|19|–|21|cm}}.{{r|dias}} Americium-241 has a [[specific activity]] of {{convert|3.43|Ci/g|GBq/g|sigfig=5|abbr=on|lk=on}}.{{r|cdc4}} It is commonly found in the form of [[americium dioxide|americium-241 dioxide]] ({{sup|241}}AmO{{sub|2}}). This isotope also has one [[nuclear isomer|meta state]], {{sup|241m}}Am, with an excitation energy of {{convert|2.2|MeV|lk=on|abbr=on}} and a [[half-life]] of {{val|1.23|u=μs}}. The presence of {{sup|241}}Am in [[plutonium]] is determined by the original concentration of [[plutonium-241]] and the sample age. Because of the low penetration of alpha radiation, americium-241 only poses a health risk when ingested or inhaled. Older samples of plutonium containing {{sup|241}}Pu contain a buildup of {{sup|241}}Am. Chemical removal of americium-241 from reworked plutonium (e.g., during reworking of [[plutonium pit]]s) may be required in some cases.

== Nucleosynthesis ==
Americium-241 has been produced in small quantities in [[nuclear reactor]]s for decades, and many kilograms of {{sup|241}}Am have been accumulated by now.{{r|g12622|page=1262}} Nevertheless, since it was first offered for sale in 1962, its price, about {{US$|1,500}} per gram of {{sup|241}}Am, remains almost unchanged owing to the very complex separation procedure.{{r|smoke}}

Americium-241 is not synthesized directly from uranium – the most common reactor material – but from plutonium-239 ({{sup|239}}Pu). The latter needs to be produced first, according to the following nuclear process:

: <math>\mathrm{^{238}_{\ 92}U\ \xrightarrow {(n,\gamma)} \ ^{239}_{\ 92}U\ \xrightarrow [23.5 \ min]{\beta^-} \ ^{239}_{\ 93}Np\ \xrightarrow [2.3565 \ d]{\beta^-} \ ^{239}_{\ 94}Pu}</math>

The capture of two neutrons by {{sup|239}}Pu (a so-called (n,γ) reaction), followed by a β-decay, results in {{sup|241}}Am:

: <math>\mathrm{^{239}_{\ 94}Pu\ \xrightarrow {2~(n,\gamma)} \ ^{241}_{\ 94}Pu\ \xrightarrow [14.35 \ yr]{\beta^-} \ ^{241}_{\ 95}Am}</math>

The plutonium present in spent nuclear fuel contains about 12% of {{sup|241}}Pu. Because it converts to {{sup|241}}Am, {{sup|241}}Pu can be extracted and may be used to generate further {{sup|241}}Am.<ref name="smoke"/> However, this process is rather slow: half of the original amount of {{sup|241}}Pu decays to {{sup|241}}Am after about 14 years, and the {{sup|241}}Am amount reaches a maximum after 70 years.{{r|BREDL}}

The obtained {{sup|241}}Am can be used for generating heavier americium isotopes by further neutron capture inside a nuclear reactor. In a [[light water reactor]] (LWR), 79% of neutron captures on {{sup|241}}Am convert to {{sup|242}}Am and 10% to its [[nuclear isomer]] {{sup|242m}}Am:<ref>{{cite journal | doi = 10.1080/18811248.2004.9715507 | date = 2012-02-07 | orig-date = 11 December 2003 | first1 = Akihiro | last1 = Sasahara | first2 = Tetsuo | last2 = Matsumura | first3 = Giorgos | last3 = Nicolaou | first4 = Dimitri | last4 = Papaioannou | title = Neutron and Gamma Ray Source Evaluation of LWR High Burn-up {{chem|UO|2}} and MOX Spent Fuels | journal = Journal of Nuclear Science and Technology | publisher = 
[[Nuclear power in Japan#Nuclear Research and professional organizations in Japan|Atomic Energy Society of Japan (AESJ)]] |volume=41 |issue=4 |pages=448–456 | issn = 0022-3131 | eissn = 1881-1248 | oclc = 2251715 | doi-access =  | s2cid = 97749940 | df = dmy-all }}</ref>

:79%:&nbsp;&nbsp; <math>\mathrm{^{241}_{\ 95}Am\ \xrightarrow {(n,\gamma)} \ ^{242}_{\ 95}Am}</math>

== Decay ==
{{Main|Radioactive decay}}Americium-241 decays mainly via [[alpha decay]], with a weak [[gamma ray]] byproduct. The α-decay is shown as follows:

<math>\mathrm{^{241\!\,}_{\ 95}Am\ \overset{432.2y}{\longrightarrow} \ ^{237}_{\ 93}Np~+~^{4}_{2}\alpha^{2+} +\gamma~59.5409~keV}</math>

The α-decay energies are {{convert|5.486|MeV|abbr=on}} for {{percentage|85|100}} of the time (the one which is widely accepted for standard α-decay energy), {{convert|5.443|MeV|abbr=on}} for 13% of the time, and {{convert|5.388|MeV|abbr=on}} for the remaining 2%.<ref>{{cite web|url = http://www.researchcompliance.uc.edu/Libraries/Isotopes/Am-241.sflb.ashx|title = AMERICIUM-241}}</ref> The [[Gamma ray|γ-ray]] energy is {{convert|59.5409|keV|abbr=on}} for the most part, with little amounts of other energies such as {{convert|13.9|keV|abbr=on}}, {{convert|17.8|keV|abbr=on}} and {{convert|26.4|keV|abbr=on}}.<ref>{{cite web | url = http://www.iaea.org/inis/collection/NCLCollectionStore/_Public/29/041/29041560.pdf | title = GAMMA RAY SPECTRUM OF AM-241 IN A BACK SCATTERING GEOMETRY USING A HIGH PURITY GERMANIUM DETECTOR}}</ref>

The second most common type of decay that americium-241 undergoes is [[spontaneous fission]], with a branching ratio of 3.6×10{{sup|−12}}<ref name=nubase>{{Nubase 2016}}</ref> and happening 1.2 times a second per gram of {{sup|241}}Am. It is written as such (the asterisk denotes an excited nucleus):

<math>\mathrm{^{241}_{\ 95}Am\longrightarrow~^{241}_{\ 95}Am^*\longrightarrow3^1_0n~+~fission~products~+energy~(\gamma)}
</math>

The least common (rarest) type of decay for americium-241 is {{SimpleNuclide|silicon|34|link=yes}} [[cluster decay]], with a branching ratio of less than 7.4×10<sup>−16</sup>.<ref name=nubase /> It is written as follows:

<math>\mathrm{^{241\!\,}_{\ 95}Am\longrightarrow^{207}_{\ 81}Tl+^{34}_{14}Si}</math>

== Applications ==

===Ionization-type smoke detector===
{{Main|Smoke detector}}Americium-241 is the only synthetic isotope to have found its way into the household, where the most common type of [[smoke detector]] (the ionization-type) uses {{chem|{{SimpleNuclide|americium|241}}O|2}} (americium-241 dioxide) as its source of [[ionizing radiation]].<ref>{{cite journal | url = http://www.uic.com.au/nip35.htm | archive-url = https://web.archive.org/web/20080303223058/http://www.uic.com.au/nip35.htm 
 | archive-date = 2008-03-03 | url-status = usurped | title = Smoke Detectors and Americium | journal = Nuclear Issues Briefing Paper | publisher = [[Uranium Information Centre]] | volume = 35 | date = May 2002 | language = en-au | access-date = 2022-09-02 | df = dmy-all }}</ref> This isotope is preferred over {{SimpleNuclide|radium|226|link=yes}}  because it emits 5{{nbsp}}times more alpha particles and relatively little harmful gamma radiation. With its half-life of {{val|432.2|u=years}}, the americium in a smoke detector decreases and includes about 3% [[neptunium]] after {{val|19|u=years}}, and about 5% after {{val|32|u=years}}. The amount of americium in a typical new smoke detector is {{convert|0.29|µg|abbr=off|lk=on}} (about 1/3000 the weight of a small grain of [[sand#composition|sand]]) with an activity of {{convert|1|µCi|kBq|lk=on}}. Some old industrial smoke detectors (notably from the Pyrotronics Corporation) can contain up to {{convert|80|μCi}}. The amount of {{sup|241}}Am declines slowly as it decays into [[neptunium-237]] ({{sup|237}}Np), a different transuranic element with a much longer half-life (about {{val|2.14|u=million years}}). The radiated [[alpha particles]] pass through an [[ionization chamber]], an air-filled space between two [[electrode]]s, which allows a small, constant [[electric current]] to pass between the capacitor plates due to the radiation ionizing the air space between. Any smoke that enters the chamber blocks/absorbs some of the alpha particles from freely passing through and reduces the ionization and therefore causes a drop in the current. The alarm's circuitry detects this drop in the current and as a result, triggers the piezoelectric buzzer to sound. Compared to the alternative optical smoke detector, the ionization smoke detector is cheaper and can detect particles which are too small to produce significant light scattering. However, it is more prone to [[false alarms]].<ref>{{cite conference | last1 = Cleary | first1 = Thomas G. | date = 2009-09-08 | title = Full-Scale Residential Smoke Alarm Performance | conference = 14th International Conference on Automatic Fire Detection | url = https://www.nist.gov/publications/full-scale-residential-smoke-alarm-performance  | location =  [[Duisburg]], [[Germany|DE]] | language = en | archive-url = https://web.archive.org/web/20210731121856/https://www.nist.gov/publications/full-scale-residential-smoke-alarm-performance | archive-date = 2021-07-31 | url-status = live | access-date = 2022-09-02 | df = dmy-all}}{{NIST-PD}}


Residential Smoke Alarm Performance, Thomas Cleary. Building and Fire Research Laboratory, National Institute of Standards and Technology; UL Smoke and Fire Dynamics Seminar. November 2007</ref><ref name="NIST">
{{cite tech report | url = https://www.nist.gov/publications/performance-home-smoke-alarms-analysis-response-several-available-technologies | date = 2007-12-01 | first1 = Richard W. | last1 = Bukowski | first2 = Richard D. | last2 = Peacock | first3 = Jason D. | last3 = Averill | first4 = Thomas G. | last4 = Cleary | first5 = Nelson P. | last5 = Bryner | first6 = William D. | last6 = Walton | first7 = Paul A. | last7 = Reneke | first8 = Erica D. | last8 = Kuligowski | display-authors = 5 | title = Home Smoke Alarms Analysis of the Response of Several Available Technologies in Residential Fire Settings | number = NIST TN 1455-1 | access-date = 2022-09-02 | url-status = live | archive-url = https://web.archive.org/web/20220308232639/https://www.nist.gov/publications/performance-home-smoke-alarms-analysis-response-several-available-technologies | archive-date = 2022-03-08 | df = dmy-all}}{{NIST-PD}}</ref><ref>{{cite report | author = <!-- not stated --> | url = https://cns-snc.ca/media/pdf_doc/ecc/smoke_am241.pdf | date = October 2008 | title = Smoke detectors and americium-241 fact sheet | publisher = [[Canadian Nuclear Society]] | access-date = 2022-09-02 | language = en-ca | archive-url = https://web.archive.org/web/20220520043222/https://cns-snc.ca/media/pdf_doc/ecc/smoke_am241.pdf | archive-date = 2022-05-20 | url-status = live | df = dmy-all }}</ref><ref>{{cite report | url = https://www.atsdr.cdc.gov/toxprofiles/tp156.pdf | title = Toxicological Profile For Americium | author1 = Agency for Toxic Substances and Disease Registry | author-link1 = Agency for Toxic Substances and Disease Registry | publisher = [[United States Department of Health and Human Services]] | access-date = 2022-09-02 | docket = CAS#: 7440-35-9 | date = April 2004 | language = en-us | location = [[Atlanta]], [[Georgia (U.S. state)|GA]] | archive-url = https://web.archive.org/web/20220727165350/https://www.atsdr.cdc.gov/toxprofiles/tp156.pdf | archive-date= 2022-07-27 | url-status= live | df = dmy-all }}{{HHS content}}</ref>

==== Manufacturing process ====
The process for making the americium used in the buttons on ionization-type smoke detectors begins with americium dioxide. The {{sup|241}}AmO{{sub|2}} is thoroughly mixed with gold, shaped into a briquette, and fused by pressure and heat at over {{convert|1470|F|C}}. A backing of silver and a front covering of gold (or an alloy of gold or [[palladium]]) are applied to the briquette and sealed by hot forging. The briquette is then processed through several stages of [[cold rolling]] to achieve the desired thickness and levels of radiation emission. The final thickness is about {{convert|0.008|in|mm}}, with the gold cover representing about one percent of the thickness. The resulting foil strip, which is about {{convert|0.8|in|mm}} wide, is cut into sections {{convert|39|in|m|sigfig=1}} long. The sources are punched out of the foil strip. Each disc, about {{convert|0.2|in|mm}} in diameter, is mounted in a metal holder, usually made of aluminium. The holder is the housing, which is the majority of what is seen on the button. The thin rim on the holder is rolled over to completely seal the cut edge around the disc.<ref>{{cite web | url = http://www.madehow.com/Volume-2/Smoke-Detector.html | title = Smoke Detector | website = How Products are Made | date = n.d. | access-date = 2022-09-01 | df = dmy-all}}</ref>

===RTG (radioisotope thermoelectric generator) power generation===
As {{sup|241}}Am has a ''roughly'' similar half-life to {{sup|238}}Pu (432.2 years vs. 87 years), it has been proposed as an active [[isotope]] of [[radioisotope thermoelectric generator]]s, for use in spacecraft.<ref name="RTG">{{cite book | first1 = G.L. | last1 = Kulcinski | title = NEEP 602 Course Notes | url = http://fti.neep.wisc.edu/neep602/SPRING00/lecture5.pdf | date = Spring 2000 | chapter = Nuclear Power in Space | publisher = [[University of Wisconsin–Madison|University of Wisconsin Fusion Technology Institute]] | at = last page | archive-url = https://web.archive.org/web/20060104181038/http://fti.neep.wisc.edu/neep602/SPRING00/lecture5.pdf | archive-date = 2006-01-04 | url-status = dead | df = dmy-all}}</ref> Even though americium-241 produces less heat and electricity than [[plutonium-238]] (the power yield is {{convert|114.7|mW/g|W/oz|disp=sqbr|abbr=off}} for {{sup|241}}Am vs. {{convert|570|mW/g|W/oz|disp=sqbr|abbr=on}} for {{sup|238}}Pu)<ref name="RTG"/> and its radiation poses a greater threat to humans owing to gamma and neutron emission, it has advantages for long duration missions with its significantly longer half-life. The [[European Space Agency]] is working on RTGs based on americium-241 for its space probes<ref name="ESAPP">{{cite web | first1 = Major S. | last1 = Chahal | title = European Space Nuclear Power Programme: UK Activities | url = http://www.oosa.unvienna.org/pdf/pres/stsc2012/tech-18E.pdf | website = [[UK Space Agency]] | date = 2012-02-08 | access-date = 2022-09-01 | archive-url = https://web.archive.org/web/20120516160844/http://www.oosa.unvienna.org/pdf/pres/stsc2012/tech-18E.pdf | archive-date = 2012-05-16 | url-status = live | via = [[United Nations Office for Outer Space Affairs]] | df = dmy-all}}</ref> as a result of the global shortage of plutonium-238 and easy access to americium-241 in Europe from nuclear waste reprocessing.<ref>{{cite news | last1 = Clark | first1 = Stephen | date = 2010-07-09 | title = Space agencies tackle waning plutonium stockpiles | url = https://spaceflightnow.com/news/n1007/09rtg/ | work = Spaceflight Now | access-date = 2022-09-02 | archive-url = https://web.archive.org/web/20220728112600/https://spaceflightnow.com/news/n1007/09rtg/ | archive-date = 2022-07-28 | url-status = live | quote = ESA's nuclear program would likely focus on americium, according to Southwood. [...] Americium-241 has a longer half-life than plutonium-238, meaning it could survive longer in space, but the isotope produces less heat and electricity. Americium is also a greater radiation hazard to humans, according to scientists.| df = dmy-all }}</ref><ref name="Ref_ff">{{cite news | first1 = Nell | last1 = Greenfieldboyce | author-link1 = Nell Greenfieldboyce | date = 2009-09-28 | url = https://www.npr.org/2009/09/28/113223613/plutonium-shortage-could-stall-space-exploration | title =  Plutonium Shortage Could Stall Space Exploration | work = [[NPR]] | access-date = 2022-09-02 | archive-url = https://web.archive.org/web/20220812003215/https://www.npr.org/2009/09/28/113223613/plutonium-shortage-could-stall-space-exploration | archive-date = 2022-08-12 | url-status = live | quote = NASA is running out of the special kind of plutonium needed to power deep space probes, worrying planetary scientists who say the U. S. urgently needs to restart production of plutonium-238. | df = dmy-all}}</ref>

Its shielding requirements in an RTG are the second lowest of all possible isotopes: only {{sup|238}}Pu requires less. An advantage over {{sup|238}}Pu is that it is produced as nuclear waste and is nearly isotopically pure. Prototype designs of {{sup|241}}Am RTGs expect 2–2.2&nbsp;W{{sub|e}}/kg for 5–50&nbsp;W{{sub|e}} RTGs design, putting {{sup|241}}Am RTGs at parity with {{sup|238}}Pu RTGs within that power range, as the vast majority of the mass of an RTG is not the isotopes, but the thermoelectrics, radiators, and isotope containment mass.<ref name="Doc3043">{{cite conference |  first1= R.M. | last1 = Ambrosi | first2 = H.R. | last2 = Williams | first3 = P. | last3 = Samara-Ratna | first4 = N.P. | last4 = Bannister | first5 = D. | last5 = Vernon | first6 = T. | last6 = Crawford | first7 = C. | last7 = Bicknell | first8 = A. | last8 = Jorden  | first9 = R. | last9 = Slade  | first10 = T. | last10 = Deacon  | first11 = J. | last11 = Konig  | first12 = M. | last12 = Jaegle  | first13 = K. | last13 = Stephenson  | display-authors = 5 | url = http://www.lpi.usra.edu/meetings/nets2012/pdf/3043.pdf | title = Development And Testing Of Americium-241 Radioisotope Thermoelectric Generator: Concept Designs And Breadboard System | conference = Lunar & Planetary Science Conference with Embedded Nuclear and Emerging Technologies for Space 2012 (NETS 2012) | publisher = [[Lunar and Planetary Institute]] | date = 2012-03-19 | location = [[The Woodlands, Texas]] | access-date = 2022-09-02 | archive-url = https://web.archive.org/web/20220325114028/https://www.lpi.usra.edu/meetings/nets2012/pdf/3043.pdf | archive-date = 2022-03-25 | url-status = live | df = dmy-all}}</ref>

===Neutron source===
Oxides of {{sup|241}}Am pressed with [[beryllium]] can be very efficient [[neutron source]]s, since they emit [[alpha particles]] during [[radioactive decay]]:

: <math>\mathrm{^{241\!\,}_{\ 95}Am\ \overset{432.2y}{\longrightarrow} \ ^{237}_{\ 93}Np\ +\ ^{4}_{2}\alpha^{2+} +\ \gamma~59.5~keV}</math>
Here americium acts as the alpha source, and beryllium produces neutrons owing to its large cross-section for the (α,n) nuclear reaction:
: <math display="inline">\mathrm{^{9}_{4}Be\ +\ ^{4}_{2}\alpha^{2+} \longrightarrow \ ^{12}_{\ 6}C\ +\ ^{1}_{0}n\ +\ \gamma}</math>

The most widespread use of {{chem|{{SimpleNuclide|americium|241}}Be}} neutron sources is a [[neutron probe]] – a device used to measure the quantity of water present in soil, as well as moisture/density for quality control in highway construction. {{sup|241}}Am neutron sources are also used in well logging applications, as well as in [[neutron radiography]], tomography, and other radiochemical investigations.{{r|NRC_Industrial_2020}}

=== Production of other elements ===
[[File:Sasahara.svg|thumb|307x307px|Chart displaying actinides and their decays and transmutations.]]Americium-241 is sometimes used as a starting material for the production of other transuranic elements and [[transactinide]]s – for example, neutron bombardment of {{sup|241}}Am yields {{sup|242}}Am:
<math>\mathrm{^{241}_{\ 95}Am\ \xrightarrow {(n,\gamma)} \ ^{242}_{\ 95}Am}</math>

From there, 82.7% of {{sup|242}}Am decays to {{sup|242}}Cm and 17.3% to {{sup|242}}Pu:

82.7% '''→''' <math>\mathrm{^{241}_{\ 95}Am\ \xrightarrow {(n,\gamma)} \ ^{242}_{\ 95}Am\ \xrightarrow [16.02 \ h]{\beta^-} \ ^{242}_{\ 96}Cm}</math>

17.3%'''→''' <math>\mathrm{^{241}_{\ 95}Am\ \xrightarrow {(n,\gamma)} \ ^{242}_{\ 95}Am\ \xrightarrow [16.02 \ h]{\beta^+} \ ^{242}_{\ 94}Pu}</math>

In the nuclear reactor, {{sup|242}}Am is also up-converted by neutron capture to {{sup|243}}Am and {{sup|244}}Am, which transforms by β-decay to {{sup|244}}Cm:
: <math>\mathrm{^{242}_{\ 95}Am\xrightarrow {(n,\gamma)}~^{243}_{\ 95}Am\ \xrightarrow {(n,\gamma)} \ ^{244}_{\ 95}Am\ \xrightarrow [10.1 \ h]{\beta^-} \ ^{244}_{\ 96}Cm}</math>

Irradiation of {{sup|241}}Am by [[carbon-12|{{sup|12|link=yes}}C]] or {{sup|22}}Ne ions yields [[einsteinium]]-253 ({{sup|253}}Es) or [[dubnium]]-263 ({{sup|263}}Db), respectively.<ref name="Binder">{{cite book | last1= Binder | first1 = Harry H. | title = Lexikon der chemischen Elemente: das Periodensystem in Fakten, Zahlen und Daten | trans-title = Lexicon of the chemical elements: the periodic table in facts, figures and dates | date = 1999 | publisher = Hirzel | language = de | isbn = 978-3-7776-0736-8 | lccn = 99200502 | oclc = 40933941 | ol = OL90844M }}</ref> Furthermore, the element [[berkelium]] ({{sup|243}}Bk isotope) had been first intentionally produced and identified by bombarding {{sup|241}}Am with alpha particles, in 1949, by the same Berkeley group, using the same {{convert|60|in|adj=on}} cyclotron that had been used for many previous experiments.{{r|g12622|page=1262}}

=== Spectrometer ===
Americium-241 has been used as a portable source of both gamma rays and alpha particles for a number of medical and industrial uses. The {{convert|59.5409|keV|abbr=on}} gamma ray emissions from {{sup|241}}Am in such sources can be used for indirect analysis of materials in [[radiography]] and [[X-ray fluorescence]] spectroscopy, as well as for quality control in fixed [[nuclear density gauge]]s and [[nuclear densometer]]s. For example, this isotope has been employed to gauge [[glass]] thickness to help create flat glass.{{r|g12622|page=1262}} Americium-241 is also suitable for calibration of gamma-ray spectrometers in the low-energy range, since its spectrum consists of nearly a single peak and negligible Compton continuum (at least three orders of magnitude lower intensity).<ref>[http://www.nndc.bnl.gov/nudat2/indx_dec.jsp Nuclear Data Viewer 2.4] {{Webarchive|url=https://web.archive.org/web/20170601010723/http://www.nndc.bnl.gov/nudat2/indx_dec.jsp |date=2017-06-01 }}, NNDC</ref>

=== Medicine ===
Gamma rays from americium-241 have been used to provide passive diagnosis of [[thyroid function]]. This medical application is now obsolete. Americium-241's gamma rays can provide reasonable quality [[Radiography|radiographs]], with a 10-minute exposure time. {{sup|241}}Am radiographs have only been taken experimentally due to the long exposure time which increases the [[Effective dose (radiation)|effective dose]] to living tissue. Reducing exposure duration reduces the chance of ionization events causing damage to cells and DNA, and is a critical component in the "time, distance, shielding" maxim used in [[radiation protection]].<ref>{{cite web|url=http://web.ornl.gov/info/reports/1962/3445605995483.pdf |title=Americium-241 Uses |url-status=dead |archive-url=https://web.archive.org/web/20151129092333/http://web.ornl.gov/info/reports/1962/3445605995483.pdf |archive-date=2015-11-29 }}</ref>

==Hazards==
{{Disputed section|Hazards|date=February 2020}}
Americium-241 has the same general hazards as other americium isotopes: it is both extremely toxic and radioactive. Though [[alpha particle|α-particles]] can be stopped by a sheet of paper, there are serious health concerns for ingestion of α-emitters. Americium and its isotopes are also very chemically toxic as well, in the form of heavy-metal toxicity. As little as {{convert|0.03|μCi}} is the maximum permissible body burden for {{sup|241}}Am.<ref>{{cite web|url=http://www.nucleonica.net/wiki/index.php?title=Americium_Am|title=Americium Am}}</ref>

Americium-241 is an α-emitter with a weak γ-ray byproduct. Safely handling americium-241 requires knowing and following proper safety precautions, as without them it would be extremely dangerous. Its specific gamma dose constant is {{val|3.14|e=-1|u=mR/hr/mCi}} or {{val|8.48|e=-5|u=mSv/hr/MBq}} at {{convert|1|m}}.<ref>{{cite web|url = http://www.researchcompliance.uc.edu/Libraries/Isotopes/Am-241.sflb.ashx|title = AMERICIUM-241 [241Am]}}</ref>

If consumed, americium-241 is excreted within a few days and only 0.05% is absorbed in the blood. From there, roughly 45% of it goes to the [[liver]] and 45% to the bones, and the remaining 10% is excreted. The uptake to the liver depends on the individual and increases with age. In the bones, americium is first deposited over [[Cortex (anatomy)|cortical]] and [[trabecula]]r surfaces and slowly redistributes over the bone with time. The biological half-life of {{sup|241}}Am is {{val|50|u=years}} in the bones and {{val|20|u=years}} in the liver, whereas in the [[gonad]]s (testicles and ovaries) it remains permanently; in all these organs, americium promotes formation of cancer cells as a result of its radioactivity.<ref>Frisch, Franz ''Crystal Clear, 100 x energy'', Bibliographisches Institut AG, Mannheim 1977, {{ISBN|3-411-01704-X}}, p. 184</ref>
[[File:Americium-241.jpg|thumb|A container of Americium-241 in a smoke detector]]

Americium-241 often enters landfills from discarded [[smoke detector]]s. The rules associated with the disposal of smoke detectors are relaxed in most jurisdictions. In the U.S., the "Radioactive Boy Scout" [[David Hahn]] was able to concentrate americium-241 from smoke detectors after managing to buy a hundred of them at remainder prices and also stealing a few.<ref name="Silverstein2005">[[Ken Silverstein]], [https://harpers.org/archive/1998/11/the-radioactive-boy-scout/ The Radioactive Boy Scout: When a teenager attempts to build a breeder reactor]. ''[[Harper's Magazine]]'', November 1998</ref><ref>{{cite news |publisher=[[Fox News]] |url=http://www.foxnews.com/story/0,2933,292111,00.html |title='Radioactive Boy Scout' Charged in Smoke Detector Theft |date=4 August 2007 |access-date=28 November 2007 |archive-url=https://web.archive.org/web/20071208062559/http://www.foxnews.com/story/0%2C2933%2C292111%2C00.html |archive-date=8 December 2007 |url-status=dead |df=dmy-all }}</ref><ref>{{cite news|work=Detroit Free Press |url=http://www.freep.com/apps/pbcs.dll/article?AID=/20070827/BUSINESS05/70827091 |title=Man dubbed 'Radioactive Boy Scout' pleads guilty |date=27 August 2007 |agency=Associated Press |access-date=27 August 2007 |archive-url=https://web.archive.org/web/20070929095926/http://www.freep.com/apps/pbcs.dll/article?AID=%2F20070827%2FBUSINESS05%2F70827091 |archive-date=29 September 2007 |url-status=dead }}</ref><ref>{{cite news |publisher=[[Fox News]] |url=https://www.foxnews.com/story/radioactive-boy-scout-sentenced-to-90-days-for-stealing-smoke-detectors |title='Radioactive Boy Scout' Sentenced to 90 Days for Stealing Smoke Detectors |date=4 October 2007 |access-date=28 November 2007 |archive-url=https://web.archive.org/web/20071113123408/http://www.foxnews.com/story/0%2C2933%2C299362%2C00.html |archive-date=2007-11-13 |url-status=live }}</ref> There have been a few cases of exposure to americium-241, the worst being [[Harold McCluskey]] who, at age 64, was exposed to 500 times the occupational standard for americium-241 as a result of an explosion in his lab. McCluskey died at age 75, not as a result of exposure, but of a [[heart disease]] which he had before the accident.<ref name="tristateherald">{{cite news|first=Annette |last=Cary |title=Doctor remembers Hanford's 'Atomic Man' |newspaper=Tri-City Herald |url=http://www.hanfordnews.com/news/2008/story/11403.html |date=25 April 2008 |access-date=17 June 2008 |url-status=dead |archive-url=https://web.archive.org/web/20100210232231/http://www.hanfordnews.com/news/2008/story/11403.html |archive-date=10 February 2010 }}</ref><ref>{{cite news  | title = Hanford nuclear workers enter site of worst contamination accident | url = http://www.billingsgazette.com/index.php?id=1&display=rednews/2005/06/03/build/nation/94-contamination.inc |date=3 June 2005 | agency = [[Associated Press]] | work = [[Billings Gazette]] |access-date=17 June 2007 |archive-url=https://web.archive.org/web/20071013185723/http://www.billingsgazette.com/newdex.php?display=rednews%2F2005%2F06%2F03%2Fbuild%2Fnation%2F94-contamination.inc |archive-date=13 October 2007 |url-status=dead }}</ref> Americium-241 has also been detected in the oceans as a result of nuclear testing conducted by various nations.<ref>{{cite journal |last1=Rozmaric |first1=M. |last2=Chamizo |first2=E. |last3=Louw |first3=D. C. |last4=López-Lora |first4=M. |last5=Blinova |first5=O. |last6=Levy |first6=I. |last7=Mudumbi |first7=B. |last8=van der Plas |first8=A. K. |last9=Garcia Tenorio |first9=R. |last10=McGinnity |first10=P. |last11=Osvath |first11=I. |date=1 January 2022 |title=Fate of anthropogenic radionuclides (90Sr, 137Cs, 238Pu, 239Pu, 240Pu, 241Am) in seawater in the northern Benguela upwelling system off Namibia |url=https://www.sciencedirect.com/science/article/pii/S004565352101986X |journal=[[Chemosphere (journal)|Chemosphere]] |volume=286 |issue=Pt 1 |pages=131514 |doi=10.1016/j.chemosphere.2021.131514 |pmid=34311394 |bibcode=2022Chmsp.28631514R |issn=0045-6535 |access-date=1 January 2024 |via=Elsevier Science Direct}}</ref>

==See also==
*[[Isotopes of americium]]

==References==
{{reflist|30em|refs=

<!-- <ref name="Shinohara_2012">{{cite journal |journal=Journal of Nuclear Science and Technology |first1=Nobuo |last1=SHINOHARA |first2=Yuichi |last2=HATSUKAWA |first3=Kentaro |last3=HATA |first4=Nobuaki |last4=KOHNO |title=Measurement of Fission Product Yields from Neutron-Induced Fission of Americium-241 |issn=0022-3131 |doi=10.1080/18811248.1999.9726203 |year=2012 |pages=232–241 |volume=36 |issue=3|doi-access=free }}</ref> -->

<ref name="dias">{{cite conference | last1 = Dias | first1 = Hemanth  | last2 = Tancock | first2 = Nigel  |last3 = Clayton | first3 = Angela | date = 2003-10-20 | title = Critical mass calculations for <sup>241</sup>Am, <sup>242m</sup>Am and <sup>243</sup>Am | conference = Proceedings of the seventh international conference on nuclear criticality safety | publisher = [[Japan Atomic Energy Research Institute]] | citeseerx = 10.1.1.540.1085 | via = [[International Atomic Energy Agency|International Atomic Energy Agency (IAEA)]] | df = dmy-all }}</ref>

<ref name=cdc4>{{cite web |url=https://www.atsdr.cdc.gov/toxprofiles/tp156-c4.pdf |title=Americium: Chemical, physical, and radiological information |pages=103–111 |publisher=Agency for Toxic Substances and Disease Registry (CDC) |access-date=24 July 2019}}</ref>

<ref name = "g12622">{{cite book | last1 = Greenwood | first1 = Norman N. | last2 = Earnshaw | first2 = Alan | title = Chemistry of the Elements | edition = 2nd | date = 1997 | publisher = [[Pergamon Press]] | isbn = 978-0-7506-3365-9 | ol = OL689297M | oclc = 1005231772 | lccn = 97036336 }}</ref>

<ref name="smoke">{{cite web | author = <!-- Not stated --> | url = http://www.world-nuclear.org/info/inf57.html | title =  Smoke detectors and americium | archive-url = https://web.archive.org/web/20081224123105/http://www.world-nuclear.org/info/inf57.html | archive-date = 2008-12-24 | website = [[World Nuclear Association]] | date = January 2009 | access-date = 2022-09-02 | url-status = dead | language = en-gb | df = dmy-all}}</ref>

<ref name="BREDL">{{cite web | url = https://www.bredl.org/sapc/Pu_ReportI.htm | title =  PLUTONIUM: THE LAST FIVE YEARS {{!}} Part I: The Trouble With Plutonium {{!}} A Review of Plutonium Destructiveness, Complexity, and Hazards | website = Blue Ridge Environmental Defense League | access-date = 2022-09-02 | archive-url = https://web.archive.org/web/20220728085430/https://www.bredl.org/sapc/Pu_ReportI.htm | archive-date = 2022-07-28 | df = dmy-all}}</ref>

<ref name="NRC_Industrial_2020">{{cite web | url = https://www.nrc.gov/materials/miau/industrial.html | date = 2020-12-02 | title = Industrial Uses of Nuclear Materials | website = [[Nuclear Regulatory Commission]] | access-date = 2022-09-02 | language = en-us | archive-url = https://web.archive.org/web/20220808144429/https://www.nrc.gov/materials/miau/industrial.html | archive-date = 2022-08-08 | url-status = live | df = dmy-all }}</ref>

}}

[[Category:Isotopes of americium]]
[[Category:Radioisotope fuels]]
[[Category:Fissile materials]]