Small-angle neutron scattering (SANS) data for the tri-n-butyl phosphate (TBP)−n-dodecane, HNO3−UO2(NO3)2 solvent extraction system have been interpreted using the Baxter model for hard spheres with surface adhesion. The increase in the scattering intensity in the low Q range observed when increasing amounts of HNO3 or UO2(NO3)2 are transferred into the organic phase has been interpreted as arising from interactions between solute particles. The SANS data have been reproduced using a 12−16 Å diameter of the hard sphere, d hs, and a 5.6k B T−7.1k B T stickiness parameter, τ-1. When in contact with an aqueous phase, TBP in n-dodecane forms small reverse micelles containing three TBP molecules. Upon extraction of water, HNO3, and UO2(NO3)2, the swollen micelles interact through attractive forces between their polar cores with a potential energy of about 2k B T and an effective Hamaker constant of about 4k B T. The intermicellar attraction, under suitable conditions, leads to third-phase formation. Upon phase splitting, most of the solutes in the original organic phase (water, TBP, HNO3, and UO2(NO3)2) separate in a continuous phase containing interspersed layers of n-dodecane.

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Recent reports have indicated that Trivalent Actinide-Lanthanide Separation by Phosphorus reagent Extraction from Aqueous Komplexes (TALSPEAK)-type separations chemistry can be improved through the replacement of bis-2-ethyl(hexyl) phosphoric acid (HDEHP) and diethylenetriamine-N,N,N 0 ,N 00 ,N 00 -pentaacetic acid (DTPA) with the weaker reagents 2-ethyl(hexyl) phosphonic acid mono-2-ethylhexyl ester (HEH [EHP]) and N-(2-hydroxyethyl) ethylenediamine-N,N 0 ,N 0 -triacetic acid (HEDTA), respectively. This modified TALSPEAK has been provided with an adjusted acronym of TALSQuEAK (Trivalent Actinide-Lanthanide Separation using Quicker Extractants and Aqueous Komplexes). Among several benefits, TALSQuEAK chemistry provides more rapid phase transfer kinetics, is less reliant on carboxylic acids to mediate lanthanide extraction, and allows a simplified thermodynamic description of the separations process that generally requires only parameters available in the literature to describe metal transfer. This article focuses on the role of carboxylic acids in aqueous ternary (M-HEDTA-carboxylate) complexes, americium/lanthanide separations, and extraction kinetics. Spectrophotometry (UV-Vis) of the Nd 3þ hypersensitive band indicates the presence of aqueous ternary Nd-Lac-HEDTA species (Lac ¼ lactate, K 111 ¼ 1.83 AE 0.01 at 1.0 mol L À1 ionic strength, Nd(HEDTA) þ Lac À À! À Nd(HEDTA)Lac À ). While lower levels (0.1 mol L À1 vs. 1.0 mol L À1 ) of carboxylic acid will still be necessary to control pH and encourage phase transfer of the heavier lanthanides, application of different carboxylic acids does not have an overwhelming impact on Ln/Am separations or extraction kinetics relative to conventional TALSPEAK separations. TALSQuEAK separations come to equilibrium in two to five minutes depending on the system pH using only 0.1 mol L À1 total lactate or citrate.

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The level structures of the neutron-rich 104 Mo and 108 Mo nuclei have been investigated by observing prompt ␥ rays emitted in the spontaneous fission of 248 Cm with the EUROGAM spectrometer. Levels with spins up to 12ប have been observed and ␥ branching obtained. The data can be satisfactorily described when 104,108 Mo are considered as axially symmetric nuclei: in 104 Mo, rotational bands based on the ground state, the one-phonon and the two-phonon ␥-vibrational states and a quasiparticle state have been observed, whereas in 108 Mo the information is limited to the yrast band and the one phonon ␥ band.