Crystal chemical design, synthesis and characterisation of U(IV)-dominant betafite phases for actinide immobilisation.

Crystal chemical design principles were applied to synthesise novel U dominant and titanium excess betafite phases CaUZrTiO and CaUZrTiO, in high yield (85-95 wt%), and ceramic density reaching 99% of theoretical. Substitution of Ti on the A-site of the pyrochlore structure, in excess of full B-site occupancy, enabled the radius ratio (r/r = 1.69) to be tuned into the pyrochlore stability field, approximately 1.

Correction: Mixed HO/H plasma-induced redox reactions of thin uranium oxide films under UHV conditions.

Correction for 'Mixed HO/H plasma-induced redox reactions of thin uranium oxide films under UHV conditions' by Ghada El Jamal , , 2021, DOI: 10.1039/d1dt01020d.

Mixed HO/H plasma-induced redox reactions of thin uranium oxide films under UHV conditions.

X-ray photoelectron spectroscopy (XPS) has been used to study the effect of mixed HO/H gas plasma on the surfaces of UO, UO and UO thin films at 400 °C. The experiments were performed under ultra-high vacuum conditions. Deconvolution of the U4f peaks into U(IV), U(V) and U(VI) components revealed the surface composition of the films after 10 min plasma exposure as a function of H concentration in the feed gas of the plasma.

Time-dependent surface modification of uranium oxides exposed to water plasma.

Thin UO films exposed to water plasma under UHV conditions have been shown to be interesting models for radiation induced oxidative dissolution of spent nuclear fuel. This is partly attributed to the fact that several of the reactive oxidizing and reducing species in a water plasma are also identified as products of radiolysis of water. Exposure of UO films to water plasma has previously been shown to lead to oxidation from U(iv) to U(v) and (vi).

X-Ray and ultraviolet photoelectron spectroscopy studies of Uranium(IV),(V) and(VI) exposed to HO-plasma under UHV conditions.

Thin films of UO2, U2O5, and UO3 were prepared in situ and exposed to reactive gas plasmas of O2, H2 and H2O vapour produced with an ECR plasma source (electron cyclotron resonance) under UHV conditions. The plasma constituents were analysed using a residual gas analyser mass spectrometer. For comparison, the thin films were also exposed to the plasma precursor gases under comparable conditions.

An Atomic-Scale Understanding of UO Surface Evolution during Anoxic Dissolution.

Our present understanding of surface dissolution of nuclear fuels such as uranium dioxide (UO) is limited by the use of nonlocal characterization techniques. Here we discuss the use of state-of-the-art scanning transmission electron microscopy (STEM) to reveal atomic-scale changes occurring to a UO thin film subjected to anoxic dissolution in deionized water. No amorphization of the UO film surface during dissolution is observed, and dissolution occurs preferentially at surface reactive sites that present as surface pits which increase in size as the dissolution proceeds.

Size Dependence of Lattice Parameter and Electronic Structure in CeO Nanoparticles.

Intrinsic properties of a compound (e.g., electronic structure, crystallographic structure, optical and magnetic properties) define notably its chemical and physical behavior.

U2O5 Film Preparation via UO2 Deposition by Direct Current Sputtering and Successive Oxidation and Reduction with Atomic Oxygen and Atomic Hydrogen.

We describe a method to produce U2O5 films in situ using the Labstation, a modular machine developed at JRC Karlsruhe. The Labstation, an essential part of the Properties of Actinides under Extreme Conditions laboratory (PAMEC), allows the preparation of films and studies of sample surfaces using surface analytical techniques such as X-ray and ultra-violet photoemission spectroscopy (XPS and UPS, respectively). All studies are made in situ, and the films, transferred under ultra-high vacuum from their preparation to an analyses chamber, are never in contact with the atmosphere.

Crystal Structure and Magnetic Properties of Uranium Hydride UH Stabilized as a Thin Film.

A new type of uranium binary hydride, UH, with the CaF crystal structure, was synthesized in a thin-film form using reactive sputter deposition at low temperatures. The material has a grain size of 50-100 nm. The lattice parameter a = (535.

Controlled synthesis of thorium and uranium oxide nanocrystals.

Very little is known about the size and shape effects on the properties of actinide compounds. As a consequence, the controlled synthesis of well-defined actinide-based nanocrystals constitutes a fundamental step before studying their corresponding properties. In this paper, we report on the non-aqueous surfactant-assisted synthesis of thorium and uranium oxide nanocrystals.

Reducing uncertainties affecting the assessment of the long-term corrosion behavior of spent nuclear fuel.

Reducing the uncertainties associated with extrapolation to very long term of corrosion data obtainable from laboratory tests on a relatively young spent nuclear fuel is a formidable challenge. In a geologic repository, spent nuclear fuel may come in contact with water tens or hundreds of thousands of years after repository closure. The corrosion behavior will depend on the fuel properties and on the conditions characterizing the near field surrounding the spent fuel at the time of water contact.

Cross-sections of the reaction 232Th(p,3n)230Pa for production of 230U for targeted alpha therapy.

(230)U/(226)Th is a promising novel alpha-emitter system for application in targeted alpha therapy of cancer. The therapeutic nuclides can be produced by proton irradiation of natural (232)Th according to the reaction (232)Th(p,3n)(230)Pa, followed by subsequent beta decay of (230)Pa to (230)U. In this study, the experimental excitation function for the (232)Th(p,3n)(230)Pa reaction up to 34 MeV proton energy has been measured using the stacked-foil technique.