Synthesis and characterization of homogeneous (U,Am)O and (U,Pu,Am)O nanopowders.

This paper details the first dedicated production of homogeneous nanocrystalline particles of mixed actinide oxide solid solutions containing americium. The target compositions were UPuAmO, UAmO and UAmO. After successful hydrothermal synthesis and chemical characterisation, the nanocrystals were sintered and their structure and behaviour under self-irradiation were studied by powder XRD.

Laser Heating Study of the High-Temperature Interactions in Nanograined Uranium Carbides.

Nanograined nuclear materials are expected to have a better performance as spallation targets and nuclear fuels than conventional materials, but many basic properties of these materials are still unknown. The present work aims to contribute to their better understanding by studying the effect of grain size on the melting and solid-solid transitions of nanograined UC. We laser-heated 4 nm-10 nm grain size samples with UC as the main phase (but containing graphite and UO as impurities) under inert gas to temperatures above 3000 K, and their behavior was studied by thermal radiance spectroscopy.

Synthesis, Characterization, and Stability of Americium Phosphate, AmPO.

AmPO was prepared by a solid-state reaction method, and its crystal structure at room temperature was solved by powder X-ray diffraction combined with Rietveld refinement. The purity of the monazite-like phase was confirmed by spectroscopic (high-resolution solid-state P NMR and Raman) and microscopic (SEM-EDX and TEM) techniques. The thermal and self-irradiation stability have been studied.

Probing the local structure of nanoscale actinide oxides: a comparison between PuO and ThO nanoparticles rules out PuO hypothesis.

Actinide research at the nanoscale is gaining fundamental interest due to environmental and industrial issues. The knowledge of the local structure and speciation of actinide nanoparticles, which possibly exhibit specific physico-chemical properties in comparison to bulk materials, would help in a better and reliable description of their behaviour and reactivity. Herein, the synthesis and relevant characterization of PuO and ThO nanoparticles displayed as dispersed colloids, nanopowders, or nanostructured oxide powders allow to establish a clear relationship between the size of the nanocrystals constituting these oxides and their corresponding An(iv) local structure investigated by EXAFS spectroscopy.

Plutonium and Americium Aluminate Perovskites.

Both AmAlO and PuAlO perovskites have been synthesized and characterized using powder X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared spectroscopy (FT-IR), and Al magic angle spinning nuclear magnetic resonance spectroscopy (MAS NMR). AmAlO perovskite showed a rhombohedral configuration (space group 3̅) in agreement with previous studies. The effect of americium α-decay on this material has been followed by XRD and Al MAS NMR analyses.

Insights into the sonochemical synthesis and properties of salt-free intrinsic plutonium colloids.

Fundamental knowledge on intrinsic plutonium colloids is important for the prediction of plutonium behaviour in the geosphere and in engineered systems. The first synthetic route to obtain salt-free intrinsic plutonium colloids by ultrasonic treatment of PuO suspensions in pure water is reported. Kinetics showed that both chemical and mechanical effects of ultrasound contribute to the mechanism of Pu colloid formation.

Further insights into the chemistry of the Bi-U-O system.

Cubic fluorite-type phases have been reported in the U(IV)O2-Bi2O3 system for the entire compositional range, but an unusual non-linear variation of the lattice parameter with uranium substitution has been observed. In the current extensive investigation of the uranium(iv) oxide-bismuth(iii) oxide system, this behaviour of the lattice parameter evolution with composition has been confirmed and its origin identified. Even under inert atmosphere at 800 °C, U(IV) oxidises to U(V)/U(VI) as a function of the substitution degree.