Transuranic elements curium

Curium is a synthetic (not natural) transuranic element of the actinide series. It was determined that curiums major valence and oxidation state was +3, similar to other elements of this series. The most stable isotope of curium is curium-247, with a half-life of 1.56xl0 years. 

Ion exchange resins provided the means of discovering elements beyond curium. A cationic resin, kept at 87" by boiling trichloroethylene, forms a column on which is poured 0.1 ml of a solution of the transuranic elements... 

Only five transuranic elements exist or are anticipated to be produced in amounts which could lead to significant environmental concentrations. These are neptunium (Np), plutonium (Pu), americium (Am), curium (Cm), and californium (Cf). Of these five, only two, plutonium and americium, have been detected and measured already in the marine environment as a result of global fallout of nuclear testing debris. The procedures described below were developed specifically to measure plutonium and americium. However, as will be expanded later, the techniques for measuring americium are also able to detect curium and californium should they be present in significant amounts in the future. 

Early Work. The irradiated fuel, upon discharge from the reactor, comprises the residual unbumt fuel, its protective cladding of magnesium alloy, zirconium or stainless steels, and fission products. The fission process yields over 70 fission product elements, while some of the excess neutrons produced from the fission reaction are captured by the uranium isotopes to yield a range of hew elements—neptunium, plutonium, americium, and curium. Neutrons are captured also by the cladding materials and yield a further variety of radioactive isotopes. To utilize the residual uranium and plutonium in further reactor cycles, it is necessary to remove the fission products and transuranic elements and it is usual to separate the uranium and plutonium this is the reprocessing operation. 

In the determination of transuranium elements (or nuclides), the most important step is separation of the elements from the sample matrix. Differences in redox properties are used for the separation of the first four elements in the series (neptunium, plutonium, americium, curium). Since the higher members exist primarily in the same oxidation state (III), separation by ion-exchange chromatography is commonly used. The lighter transuranic elements can be determined by common chemical methods, and trace amounts are usually determined by radiometric methods such as a-spectrometry. 

J3AI + Jn iiNa + pie represents the bombardment of aluminum with neutrons to produce an isotope of sodium and helium nuclei (alpha particles). All transuranic elements above curium, atomic number 96, are artificially radioactive because they do not occur in nature. Even neptunium, plutonium, americium. 

To estimate the environmental impact caused by nuclear fuel cycle of the SVBR-75/100, the value of specific radiotoxicity of the produced transuranic elements (neptunium, plutonium, americium and curium) and long-lived fission products (technetium-99, iodine-129 and caesium-135) was taken as a criterion, as a function of the electric energy produced. When this value decreases with energy production, the environmental impact of the nuclear fuel cycle can be considered friendly . The radiotoxicity characteristic adopted was the volume of water necessary to dilute some quantity of radionuclides to the concentrations for which the specific radioactivity of the solution meets the sanitary requirements for drinking water. 

Americium, Curium, and Californium Purification. These elements, together with any lanthanides in the sample or added as carriers, pass through the anion exchange column used to remove plutonium. This fraction is purified to remove natural-series radionuclides which interfere with americium, curium, or californium measurements as well as stable elements which plate with the transuranics and produce spectral degradation. This latter consideration is especially important for lanthanides as neodymium is used as a carrier. Two lanthanide/actinide separation cycles immediately before electroplating are essential for acceptable plate quality. 

After their success with neptunium and plutonium, Seaborg and his collaborators continued to look for more transuranics. (These collaborators included other scientists and graduate students who contributed many ideas and most of the work, and we regret that they must be consigned to a footnote.) They used cyclotron bombardment, a variety of targets, and microchemical techniques developed by Hahn. Americium and curium (elements number 95 and 96) were discovered in wartime at the Metallurgical Laboratory of the University of Chicago,... 

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