Uranium intermetallics

These cases can be contrasted by most uranium intermetallics, which have Fermi surfaces in good agreement with LDA calculations which treat the f electrons as band states (IQ. In the one case where a mixed valent Fermi surface is known (CeSno), it is also in excellent agreement with an LDA f band calculation (T8-19L with a mass renormalization of five due to a self-energy correction resulting from virtual spin fluctuation excitations (2Q). Notice the different dynamic correlations used to explain the mass renormalizations in the f core and f band cases. 

Various photoemission techniques are a powerful tool for the investigation of especially large-scale features of the occupied electronic states. Numerous photoemission data are available mainly on the uranium intermetallics. These were obtained by all possible kinds of excitations such as X-ray photoemission (XPS), ultraviolet high-resolution photoemission (UPS), or synchrotron-radiation-excited photoemission with the possibility of tuning the energy of the incident radiation. The Bremsstrahlung isochromat spectroscopy (BIS) is a probe of the empty electronic states above EF. 

A local-moment behaviour resulting from an apparent localization of the 5f states was observed for UPd3 where U adopts a 5f2 configuration. This situation seems to be exceptional among all the uranium intermetallics which is supported by the following experimental findings ... 

Mossbauer spectroscopy is in reality the only tool to investigate the hyperfine interactions at the uranium site in such exotic uranium intermetallics. There are several uranium isotopes such as U, and U. The natural abundances of these isotopes are 0.005,0.72, and 99.27%, respectively. The ground state of the nuclei iszeroin U and due to which it is impossible to carryout NMR experiments. Although the isotope whose nuclear ground state... 

Plots of the hyperfine field at nuclei against the ordered magnetic moments in uranium intermetallics. Open circles are the results reported by Ref. 2. Closed circles were the results calculated in free ions of uranium atoms. Closed squares were results measured in this work. 

Mossbauer measurements of exotic uranium compounds were carried out in the present work. Systematic measurements of uranium intermetallics reveal that the hyperfine coupling constant is ISOTZ/te at uranium nuclei. This hyperfine coupling constant depends on the hybridization between 5f and conduction electrons as well as on the... 

During recent years it has become obvious that the properties of the so-called anomalous rare earth compounds (in particular cerium-based systems) show many similarities to the light-actinide (U, Np, Pu) compounds. The best known property which reflects the similarity is the appearance of heavy-fermion phenomena in many cerium and uranium intermetallics. 

In this process, uranium metal is electrodeposited at the cathode, while plutonium and other transuranium elements remain in the molten salt as trichlorides. Plutonium is reduced in a second step at a metallic cathode to produce Cd—Pu intermetallics. The refined plutonium and uranium metals can then be refabricated into metallic fuel (137). 

Selenium and Tellerium Tantalum is attacked by selenium and tellurium vapours at temperatures higher than 80°C. Only slight attack is observed on the metal by liquid selenides and tellurides of ytirum, the rare earths, and uranium at temperatures of 1300 to 2100°C, and tantalum is considered to be a satisfactory material in which to handle these intermetallic compounds. 

A 50 weight % uranium alloy, free of interstitial impurities such as hydrogen, would consist of the intermetallic compound UZr2, designated as the delta phase. 

The solid (U,Pu)2Zni7 intermetallic compound, containing FP-3 and selective FP-4 fission products for proliferation resistance is vacuum distilled to remove the zinc, which is recycled. The uranium/plutonium concentrate is injection cast into rods suitable as feed to the refabrication process. 

The fuel is dissolved during reduction of the mixed oxides by calcium. This oxide reduction operation is done in the presence of a CaCl2-CaF2 salt and a Cu-Mg alloy. The FP-2 elements and the CaO reaction product are taken up by the salt and the reduced uranium, plutonium, FP-3, and FP-4 elements are taken up by the alloy. Uranium is present in excess of its solubility limit and precipitates as the UCu5 intermetallic compound. 

The solubilities of uranium, plutonium, and thorium in magnesium at 650°C are 0.002 wt %, 55 wt %, and 44 wt %, respectively. Thus, assuming no solute interaction, uranium is essentially insoluble in magnesium, while plutonium is quite soluble and good separation may be effected. While precipitation of an insoluble phase from solution would appear to be a straightforward process, the behavior of a solute in a given metal or alloy may differ from its behavior when influenced by the inclusion of other solutes. One element may increase or suppress the solubility of another through coprecipitation or intermetallic compound formation. Such effects must be determined experimentally. 

Photo ESP measurements have been reported for the series of intermetallic compounds US, USe and UTe (21). The ESP for these compounds is negative for all b m. The magnetic moment of uranium compounds is predominately determined by the occupied 5f electrons. However, the photoyield of the f-electrons at photon energies less that 11 eV is very small relative to s, p or d electron yields. Thus, the observed photoelectron spin... 

Possible leductants. Elements that might be considered for reducing UO2, UF4, or UCI4 to metallic uranium are hydrogen, sodium, magnesium, or calcium. Carbon is impractical because of formation of uranium carbide, and aluminum is undesirable because it forms an intermetallic compound with uranium. Sodium, magnesium, and calcium do not do this. 

Gross, P., Levi, D. L., Lewin, R. H., Aetivities in uranium-bismuth alloys and the free energies of uranium-bismuth eompounds. The physical chemistiy of metallic solutions and intermetallic com-ponnds, NPL Symposium No.9, pp.3G2-3G9, London, (1959). Cited on page 519. 

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