Investigation of electrorefining of metallic alloy fuel onto solid Al cathodes

This work concerned the electrorefining of UZr and UPuZr alloys on a solid aluminium cathode, in the LiCl-KCl eutectic melt containing U3+, Pu3+, Np3+, Zr2+ or Zr 4+, Am3+, Nd3+, Y3+, Ce3+ and Gd3+ chlorides. During constant current electrolyses, the use of a cathodic cut-off potential (-1.25 V vs. Ag/AgCl) allowed to selectively deposit actinides (mainly U), while lanthanides remainedin the salt. The aim was to determine the maximal load achievable on a single aluminium electrode. The total exchange charge was 4300 C, which represents the deposition of 3.72 g of actinides in 4.17 g Al, yielding a composition of 44.6 wt% An in Al. It was shown that the melting of the cathode contributed to increase the total amount of actinides deposited on the aluminium

Modeling the actinides with disordered local moments

A first-principles disordered local moment (DLM) picture within the local-spin-density and coherent potential approximations (LSDA+CPA) of the actinides is presented. The parameter free theory gives an accurate description of bond lengths and bulk modulus. The case of $\delta$-Pu is studied in particular and the calculated density of states is compared to data from photo-electron spectroscopy. The relation between the DLM description, the dynamical mean field approach and spin-polarized magnetically ordered modeling is discussed.Comment: 6 pages, 4 figure

Predicting the optical observables for nucleon scattering on even-even actinides

Previously derived Lane consistent dispersive coupled-channel optical model for nucleon scattering on $^{232}$Th and $^{238}$U nuclei is extended to describe scattering on even-even actinides with $Z=$90--98. A soft-rotator-model (SRM) description of the low-lying nuclear structure is used, where SRM Hamiltonian parameters are adjusted to the observed collective levels of the target nucleus. SRM nuclear wave functions (mixed in $K$ quantum number) have been used to calculate coupling matrix elements of the generalized optical model. The "effective" deformations that define inter-band couplings are derived from SRM Hamiltonian parameters. Conservation of nuclear volume is enforced by introducing a dynamic monopolar term to the deformed potential leading to additional couplings between rotational bands. Fitted static deformation parameters are in very good agreement with those derived by Wang and collaborators using the Weizs\"acker-Skyrme global mass model (WS4), allowing to use the latter to predict cross section for nuclei without experimental data. A good description of scarce "optical" experimental database is achieved. SRM couplings and volume conservation allow a precise calculation of the compound-nucleus formation cross sections, which is significantly different from the one calculated with rigid-rotor potentials coupling the ground-state rotational band. Derived parameters can be used to describe both neutron and proton induced reactions.Comment: 6 pages, 4 figures, 5 table

Evaluation of diffusive gradients in thin-films using a Diphonix® resin for monitoring dissolved uranium in natural waters

Commercially available Diphonix® resin (TrisKem International) was evaluated as a receiving phase for use with the diffusive gradients in thin-films (DGT) passive sampler for measuring uranium. This resin has a high partition coefficient for actinides and is used in the nuclear industry. Other resins used as receiving phases with DGT for measuring uranium have been prone to saturation and significant chemical interferences. The performance of the device was evaluated in the laboratory and in field trials. In laboratory experiments uptake of uranium (all 100% efficiency) by the resin was unaffected by varying pH (4–9), ionic strength (0.01–1.00 M, as NaNO3) and varying aqueous concentrations of Ca2+ (100–500 mg L−1) and HCO3− (100–500 mg L−1). Due to the high partition coefficient of Diphonex®, several elution techniques for uranium were evaluated. The optimal eluent mixture was 1 M NaOH/1 M H2O2, eluting 90% of the uranium from the resin. Uptake of uranium was linear (R2 = 0.99) over time (5 days) in laboratory experiments using artificial freshwater showing no saturation effects of the resin. In field deployments (River Lambourn, UK) the devices quantitatively accumulated uranium for up to 7 days. In both studies uptake of uranium matched that theoretically predicted for the DGT. Similar experiments in seawater did not follow the DGT theoretical uptake and the Diphonix® appeared to be capacity limited and also affected by matrix interferences. Isotopes of uranium (U235/U238) were measured in both environments with a precision and accuracy of 1.6–2.2% and 1.2–1.4%, respectively. This initial study shows the potential of using Diphonix®-DGT for monitoring of uranium in the aquatic environment

On the Convergence of the Electronic Structure Properties of the FCC Americium (001) Surface

Electronic and magnetic properties of the fcc Americium (001) surface have been investigated via full-potential all-electron density-functional electronic structure calculations at both scalar and fully relativistic levels. Effects of various theoretical approximations on the fcc Am (001) surface properties have been thoroughly examined. The ground state of fcc Am (001) surface is found to be anti-ferromagnetic with spin-orbit coupling included (AFM-SO). At the ground state, the magnetic moment of fcc Am (001) surface is predicted to be zero. Our current study predicts the semi-infinite surface energy and the work function for fcc Am (001) surface at the ground state to be approximately 0.82 J/m2 and 2.93 eV respectively. In addition, the quantum size effects of surface energy and work function on the fcc Am (001) surface have been examined up to 7 layers at various theoretical levels. Results indicate that a three layer film surface model may be sufficient for future atomic and molecular adsorption studies on the fcc Am (001) surface, if the primary quantity of interest is the chemisorption energy.Comment: 34 pages, 9 figure