Americium

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iso	NA	half-life	DM	DE (MeV)	DP WikiDoc Resources for Americium Articles Most recent articles on Americium Most cited articles on Americium Review articles on Americium Articles on Americium in N Eng J Med, Lancet, BMJ Media Powerpoint slides on Americium Images of Americium Photos of Americium Podcasts & MP3s on Americium Videos on Americium Evidence Based Medicine Cochrane Collaboration on Americium Bandolier on Americium TRIP on Americium Clinical Trials Ongoing Trials on Americium at Clinical Trials.gov Trial results on Americium Clinical Trials on Americium at Google Guidelines / Policies / Govt US National Guidelines Clearinghouse on Americium NICE Guidance on Americium NHS PRODIGY Guidance FDA on Americium CDC on Americium Books Books on Americium News Americium in the news Be alerted to news on Americium News trends on Americium Commentary Blogs on Americium Definitions Definitions of Americium Patient Resources / Community Patient resources on Americium Discussion groups on Americium Patient Handouts on Americium Directions to Hospitals Treating Americium Risk calculators and risk factors for Americium Healthcare Provider Resources Symptoms of Americium Causes & Risk Factors for Americium Diagnostic studies for Americium Treatment of Americium Continuing Medical Education (CME) CME Programs on Americium International Americium en Espanol Americium en Francais Business Americium in the Marketplace Patents on Americium Experimental / Informatics List of terms related to Americium Overview Americium (IPA: Template:IPA) is a synthetic element that has the symbol Am and atomic number 95. A radioactive metallic element, americium is an actinide that was obtained by bombarding plutonium with neutrons and was the fourth transuranic element to be discovered. It was named for the Americas, by analogy with europium. Notable characteristics Pure americium has a silvery and white lustre. At room temperatures it slowly tarnishes in dry air. It is more silvery than plutonium or neptunium and apparently more malleable than neptunium or uranium. Alpha emission from 241Am is approximately three times that of radium. Gram quantities of 241Am emit intense gamma rays which creates a serious exposure problem for anyone handling the element. Americium is also fissile; the critical mass for an unreflected sphere of 241Am is approximately 60 kilograms. It is unlikely that Americium would be used as a weapons material, as its minimum critical mass is considerably larger than more readily obtained plutonium or uranium isotopes. [6] Please see Actinides in the environment for more details of the environmental aspects of this element. Applications This element can be produced in kilogram amounts and has some uses (mostly 241Am since it is easier to produce relatively pure samples of this isotope). Americium has found its way into the household, where one type of smoke detector contains a tiny amount (about 0.2 microgram) of 241Am as a source of ionizing radiation. 241Am has been used as a portable gamma ray source for use in radiography. The element has also been employed to gauge glass thickness to help create flat glass. 242Am is a neutron emitter and has found uses in neutron radiography. It has also been cited for use as an advanced nuclear rocket propulsion fuel[7]. This isotope is, however, extremely expensive to produce in usable quantities. History Americium was first isolated by Glenn T. Seaborg, Leon O. Morgan, Ralph A. James, and Albert Ghiorso in late 1944 at the wartime Metallurgical Laboratory at the University of Chicago (now known as Argonne National Laboratory). The team created the isotope 241Am by subjecting 239Pu to successive neutron capture reactions in a nuclear reactor. This created 240Pu and then 241Pu which in turn decayed into 241Am via beta decay. Seaborg was granted U.S. Patent 3,156,523 for "Element 95 and Method of Producing Said Element," whose unusually terse claim number 1 reads simply, "Element 95." The discovery of americium and curium was first announced informally on a children's quiz show in 1945. [8] Isotopes Main article: isotopes of americium File:Americium.jpg Sample of Americium 18 radioisotopes of americium have been characterized, with the most stable being 243Am with a half-life of 7370 years, and 241Am with a half-life of 432.7 years. All of the remaining radioactive isotopes have half-lives that are less than 51 hours, and the majority of these have half-lives that are less than 100 minutes. This element also has 8 meta states, with the most stable being 242mAm (t½ 141 years). The isotopes of americium range in atomic weight from 231.046 u (231Am) to 249.078 u (249Am). Chemistry In aqueous systems the most common oxidation state is +3. It is very much harder to oxidize Am(III) to Am(IV) than it is to oxidise Pu(III) to Pu(IV). Currently the solvent extraction chemistry of americium is important as in several areas of the world scientists are working on reducing the medium term radiotoxicity of the waste from the reprocessing of used nuclear fuel. See liquid-liquid extraction for some examples of the solvent extraction of americium. Americium, unlike uranium, does not readily form a dioxide americyl core (AmO2). [9] This is because americium is very hard to oxidise above the +3 oxidation state when it is in an aqeuous solution. In the environment, this americyl core could complex with carbonate as well as other oxygen moieties (OH-, NO2-, NO3-, and SO4-2) to form charged complexes which tend to be readily mobile with low affinities to soil. AmO2(OH)+1 AmO2(OH)2+2 AmO2CO3+1 AmO2(CO3)2-1 AmO2(CO3)3-3 A large amount of work has been done on the solvent extraction of americium, as it is the case that americium and the other transplutonium elements are responsible for the majority of the long lived radiotoxicity of spent nuclear fuel. It is thought that by removal of the americium and curium that the used fuel will only need to be isolated from man and his environment for a shorter time than that required for the isolation of untreated used fuel. One recent EU funded project on this topic was known by the codename "EUROPART". Within this project triazines and other compounds were studied as potential extraction agents. References External links Los Alamos National Laboratory - Americium Guide to the Elements - Revised Edition, Albert Stwertka, (Oxford University Press; 1998) ISBN 0-19-508083-1 It's Elemental - Americium ATSDR - Public Health Statement: Americium Nuclides and Isotopes - 14th Edition, GE Nuclear Energy, 1989. Patent US patent 3156523, Glenn T. Seaborg, "Element 95 and Method of Producing Said Element", issued 1964-11-10  CEA Can the minor actinide, americium-241, be transmuted by thermal neutrons? American Institude of Physics Conference Proceedings WebElements.com - Americium (also used as a reference) NLM Hazardous Substances Databank - Americium, radioactive