Neptunium and plutonium

The new elements neptunium and plutonium have been produced in quantity by neutron bombardment of uranium. Subsequently many isotopes have been obtained by transmutation and synthetic isotopes of elements such as Ac and Pa are more easily obtained than the naturally occurring species. Synthetic species of lighter elements, e.g. Tc and Pm are also prepared. 

Initially, the only means of obtaining elements higher than uranium was by a-particle bombardment of uranium in the cyclotron, and it was by this means that the first, exceedingly minute amounts of neptunium and plutonium were obtained. The separation of these elements from other products and from uranium was difficult methods were devised involving co-precipitation of the minute amounts of their salts on a larger amount of a precipitate with a similar crystal structure (the carrier ). The properties were studied, using quantities of the order of 10 g in volumes of... 

One of the major advances of science in the first half of this century was the synthesis of ten elements beyond uranium. Glenn T. Seaborg participated in the discovery oj most of these, a sufficient tribute to his outstanding ability as a scientist. For the first such discoveries, those of neptunium and plutonium, he shared with Professor Edwin M. McMillan the Nobel Prize in Chemistry for 1951. 

Burney, G. A. Separation of Neptunium and Plutonium by Anion Exchange. U.S. AEC Report DP-689, E. I. duPont de Nemours Co., Savannah River Laboratory, Aiken, SC, 1962. 

ICP-MS (inductively coupled plasma mass spectrometry) is frequently used for determining ultratrace amounts of technetium [9]. In spite of the high cost of the equipment, this detection method is far superior to other radiometric methods as regards sensitivity. When a double focussing high-resolution system is used (HR-ICP-MS) and an ultrasonic nebulizer is introduced [10], the detection limit is in the order 0.002 mBq. The ICP-MS method has been successfully applied to the determination of environmental "Tc as well as to other long-lived radionuclides of neptunium and plutonium in the environment. 

Riglet, Ch. Robouch, P. Vitorge, P. Standard potentials of the (M02 /M0j) and redox systems for neptunium and plutonium. Radiochim. 

If an actinide metal is available in sufficient quantity to form a rod or an electrode, very efficient methods of purification are applicable electrorefining, zone melting, and electrotransport. Thorium, uranium, neptunium, and plutonium metals have been refined by electrolysis in molten salts (84). An electrode of impure metal is dissolved anodically in a molten salt bath (e.g., in LiCl/KCl eutectic) the metal is deposited electrochemically on the cathode as a solid or a liquid (19, 24). To date, the purest Np and Pu metals have been produced by this technique. 

Heavier isotopes Es-253, Es-254 and Es-255 can be produced in a nuclear reactor by multiple neutron capture reactions that may occur when uranium, neptunium and plutonium isotopes are irradiated under intense neutron flux. These and other isotopes also are produced during thermonuclear explosions. 

Fluorine is used in the separation of uranium, neptunium and plutonium isotopes by converting them into hexafluorides followed by gaseous diffusion then recovering these elements from nuclear reactors. It is used also as an oxidizer in rocket-fuel mixtures. Other applications are production of many fluo-ro compounds of commercial importance, such as sulfur hexafluoride, chlorine trifluoride and various fluorocarbons. 

The remaining exceptions concern the lanthanide series, where samarium at room temperature has a particular hexagonal structure and especially the lower actinides uranium, neptunium, and plutonium. Here the departure from simple symmetry is particularly pronounced. Comparing these three elements with other metals having partly filled inner shells (transition elements and lanthanides), U, Pu, Np have the lowest symmetry at room temperature, normal pressure. This particular crystallographic character is the reason why Pearson did not succeed to fit the alpha forms of U, Pu, and Np, as well as gamma-Pu into his comprehensive classification of metallic structures and treated them as idiosyncratic structures . Recent theoretical considerations reveal that the appearance of low symmetries in the actinide series is intimately linked to the behaviour of the 5f electrons. 

A system particularly studied from a thermodynamic point of view is the monocarbide (AnCi x) system. A range of stability for carbon deficient compositions in the monocarbides is present in many metal-carbon phase diagrams. Table 6 shows the composition range at room temperature for actinide monocarbides. The non-stoichiometry range is very limited for uranium monocarbide for neptunium and plutonium monocarbides, the stoichiometric AmCj oo composition is not stable. 

In 1970, Hill pointed out that one may classify uranium, neptunium and plutonium compounds into a magnetic and non magnetic group depending on interactinide distance dAn-An (sce Chap. A) with a critical value of about 3.4 A. This systematics clearly evidences a localization process related to direct 5 f-5 f overlap. As we said at the beginning of this section, the critical distance may be viewed from the 2 different points of view... 

Since this is so, it was inevitable that as soon as Seaborg and his collaborators had clearly established the identity and properties of neptunium and plutonium, they would look for the next higher elements, numbers 95 and 96. The general similarity in chemical properties of uranium, neptunium, and plutonium led Seaborg to believe that these new elements could be isolated by methods similar to those already used. 

Americium and curium injected into animals are distributed to the extent of about 25 per cent in bone, but unlike neptunium and plutonium, about 70 per cent of the injected dose is found in the liver. Loss from the... 

Barrero Moreno et al.49 determined neptunium and plutonium in the presence of high concentrations of uranium by ion chromatography coupled to ICP-MS. 

Allard, B., Kipatsi, H. and Liljenzin, J. 0., "Calculated Species of Uranium, Neptunium and Plutonium in Neutral Aqueous Solution", subm. to Radiochem. Radioanal. Lett. 

The only examples of compounds of this type are the borohydrides, MIV(BH4)4 (MIV = Th-Pu) and MIV(MeBH3)4 (MIV = Th, U, Np). These compounds are conveniently prepared by reaction, for example, of the metal tetrafluoride with A1(BH4)3 in a sealed tube, followed by vacuum sublimation of the product.159 The neptunium and plutonium compounds are liquids at room temperature and are more volatile than the thorium, protactinium or uranium analogues. 

MCMILLAN, EDWIN M. (1907-1991). An American physicist who won the Nobel prize in chemistry in 1951 along with Glenn T. Seaborg lor their discoveries In the chemistry of the transuranium elements. His work included research in nuclear physics and particle accelerator development as well as microwave radar and sonar. He and his colleagues discovered neptunium and plutonium. He was the recipient of the Atoms for Peace prize in 1963. His Ph D. in Physics was awarded from Princeton University. 

The most widely used neutral extractants, however, are the organophosphoms compounds, of which the ester, TBP, is the most important. TBP forms complexes with the actinide elements thorium, uranium, neptunium, and plutonium by bonding to the central metal atom via the phosphoryl oxygen in the structure... 

Birkett, J.E., Carrott, M.J., Fox, O.D. et al. 2007. Controlling neptunium and plutonium within single cycle solvent extraction flowsheets for advanced fuel cycles. J. Nucl. Sci. Technol. 44 (3) 337-343. 

A mixture of uranium, neptunium, and plutonium to fabricate new mixed actinide-fuels (either metallic or oxides)... 

Bergeonneau, P., C. Jaonen, M. Germain, and A. Bathellier. 1979. Uranium, Neptunium, and Plutonium Kinetics of Extraction by Tributylphosphate and Trilaurylamine in a Centrifugal Contactor. Proceedings of International Solvent Extraction Conference (ISEC 77), September 9-16, 1977, Toronto, Canada, vol. 2, 612-619. 

The actinides include another part of the periodic table called the transuranium elements, which begin with neptunium (atomic number 93) and end with roentgenium (atomic number 111) back up in Period 7. Neptunium and plutonium are the only... 

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