Neptunium chemical separation

Plutonium is manufactured in megagram quantities neptunium, americium, and curium in kilogram quantities californium in gram amounts berkelium in 100-milligram amounts and einsteinium in milligram quantities. Chemical separations play a key role in the manufacture of actinide elements, as well as in their recovery, and analysis in the nuclear fuel cycle. This collection of timely and state-of-the-art topics emphasizes the continuing importance of actinide separations processes. 

Plutonium. (74) Plutonium can be chemically separated from all other elements except neptunium and counted quantitatively by this procedure, and the 4.78 MeV Np peak can be resolved by its energy difference from 5.15 MeV The... 

Chemical separation. Current concepts for high-efficiency separation of actinides call for improved plutonium recovery, coextraction of uranium and neptunium with subsequent partitioning by valence control, and extraction of amercium and curium from the HAW stream. There are a number of major problems to be solved before a technically feasible process will be available. 

After Abelson returned to Washington, McMillan pressed on. Unstable neptunium decayed by beta emission with a 2.3-day half-life he suspected it decayed to element 94. By analogy with uranium, which emits alpha particles naturally, element 94 should also be a natural alpha emitter. McMillan therefore looked for alphas with ranges different from the uranium alphas coming off his mixed luranium-neptunium samples. By autumn he had identified them. He tried some chemical separations, finding that the alpha-activity did not belong to an isotope of protactinium, uranium or neptunium. He was that close. 

Neptunium, plutonium, americium, and curium To improve the sensitivity, neptunium, plutonium, americium, and curium were measured after chemical separation. For americium and curium, chemical separation and radiometric measurement were the only alternative due to the short half-lives, a-spectrometry is more sensitive than ICP-MS. 

The actinides uranium and thorium occur in nature as primordial matter. Actinium and protactinium occur in nature as daughters of thorium and uranium, while small amounts of neptunium and plutonium are present as a result of neutron-capture reactions of uranium. All other members of the series are man-made. Separation chemistry has been central to the isolation and purification of the actinides since their discovery. The formation of the transplutonium actinides was established only as a result of chemical-separation procedures developed specifically for that purpose. The continued application of separation science has resulted in the availability of weighable quantities of the actinides to fermium. Separation procedures are central to one-atom-at-a-time chemistry used to identify synthetic trans-actinide (superheavy) elements to element 107 and above (Report of a Workshop on Transactinium Science 1990). 

The first transuranium element, neptunium, was discovered in 1940 by E. M. McMillan and P. H. Abelson. They were able to chemically separate and identify element 93 formed in the following reaction sequences [Eq. (4)] ... 

Chemical Separation of Neptunium-239. In most neutron activation analyses, a chemical separation Is made to Isolate the radioactivity of the element from all other radioactive species in the sample. Usually an "Isotopic carrier"--a known amount of the natural Inactive element—Is added to the solutions... 

Uranium-239 [13982-01 -9] has a half-life of 23.5 min neptunium-239 [13968-59-7] has a half-life of 2.355 d. Recycling or reprocessing of spent fuel involves separation of plutonium from uranium and from bulk fission product isotopes (see Nuclearreactors, chemical reprocessing). 

All the early work on plutonium was done with unweighable amounts on a tracer scale. When it became apparent that large amounts would be needed for the atomic bomb, it was necessary to have a more detailed knowledge of the chemical properties of this element. Intensive bombardment of hundreds of pounds of uranium was therefore begun in the cyclotrons at Berkeley and at Washington University in St. Louis. Sepa-ration of plutonium from neptunium was based on the fact that neptunium is oxidized by bromate while plutonium is not, and that reduced fluorides of the two metals are carried down by precipitation of rare earth fluorides, while the fluorides of the oxidized states of the two elements are not. Therefore a separation results by repeated bromate oxidations and precipitations with rare earth fluorides. 

The purpose of this study was to investigate the anionic exchange behavior of neptunium(V) in sulfate-sulfuric acid, because neptunium is often present as a contaminant during the separation of other actinides (l ). Sulfuric acid systems are seldom utilized in industrial processes, but are often used as part of a laboratory analytical procedure. Literature on neptunium in HC101, HC1, HC1-HF, and HNO3 is quite complete, but the information on the H2S0l system is sketchy at best. There is one report 2) that neptunium(V) is adsorbed strongly on Dowex 2 resin from 0.1 IT to 1 IT H SOip Our measurements indicate that there is very little adsorption of Np(V) on Dowex 1 resin even at low concentrations of sulfate-sulfuric acid. We believe the differences in chemical structure of the two resins are not sufficient to explain the disparity in adsorption. 

Separation of Actinides from the Samples of Irradiated Nuclear Fuels. For the purpose of chemical measurements of burnup and other parameters such as accumulation of transuranium nuclides in irradiated nuclear fuels, an ion-exchange method has been developed to separate systematically the transuranium elements and some fission products selected for burnup monitors (16) Anion exchange was used in hydrochloric acid media to separate the groups of uranium, of neptunium and plutonium, and of the transplutonium elements. Then, cation and anion exchange are combined and applied to each of those groups for further separation and purification. Uranium, neptunium, plutonium, americium and curium can be separated quantitatively and systematically from a spent fuel specimen, as well as cesium and neodymium fission products. 

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. 

Chemicals of normal reagent-grade purity suffice for the separation of analytes that do not occur in nature there should be no important impact on the analyses of samples of neptunium, plutonium, americium, or curium, provided reagent volumes are kept small so that mass is not introduced into the final samples. For all other analytes, reagents that... 

Pu, Zr(+Nb), and Ce and iTithenlum complexes. Neptunium, plutonium, and cerium are made less extractable by reduction to lower oxidation states. Favorable separation of tiranlum from the other elements may be achieved by control.of the nitric acid and saltlng-out agent concentrations. Free halogens are extracted. These elements may be eliminated from solution prior to uranliim extraction. The halogens also combine chemically with a number of solvents eg,. 

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