JRP CALL information
Supported By

European Commission

Short description of the work
X-ray absorption spectroscopy (XAS) measurements have been performed on ground microspheres, consisting of Nd(y)U(1-y)O(2) with variable neodymium contents, at the Rossendorf Beamline (HZDR-ROBL) beamline (ESRF, Grenoble, France) to investigate solid solution characteristics.
Spherical particles with a diameter of about 1000 µm were prepared by the sol-gel method via internal gelation at Forschungszentrum Jülich GmbH (FZJ). The spherical shape was proven by scanning electron microscopy (SEM). Furthermore, the chemical composition, morphology and homogeneity was studied by SEM coupled with an energy dispersive X-ray spectroscope (EDX), cross checks were performed with dissolved particles in an inductively coupled plasma - mass spectrometer (ICP-MS) system at FZJ.
Long range order characterization was performed by applying X-ray powder technique. Single phase material was identified, the results were confirmed by the XAS investigations at the associated pooled facility. Further data analyses will be performed to determine the Nd-O and U-O bond length, as well as the oxidation state of uranium and the oxygen to metal ratio.

 

Short description of the work
Seven samples of 1 mM Am(III) in the presence of 1 M sodium formate at varying pH (2.0 and 4.0) have been prepared at the Institute of Nuclear Waste Disposal (KIT, Karlsruhe, Germany). Due to the stable operation at the ESRF it was possible to measure a minimum of 10 scans for each sample.
The obtained EXAFS spectra provide a sufficient quality to ensure an evaluation up to k = 10-11 Å-1. The data will now be evaluated to obtain the molecular structure (coordination numbers, Am-O and Am-C distances) of the different Am(III) formate species as a function of the pH to determine whether formate binds mono- or bidentate to the actinide ion. Furthermore, the spectroscopic results will be complemented by iterative transformation factor analysis, thermodynamic speciation calculations and quantum chemical calculations. The final result will help to improve the general understanding of actinide geochemistry.
The results will be presented at national and international conferences and meetings. Furthermore, a publication of the data in a peer review journal is planned.

 

Short description of the work
A series of different composition prototypical corium materials were synthesised at the JRC-ITU and Laser heated (and cooled) at controlled atmosphere simulating high temperature phase changes during severe accidents. In order to fully understand the behaviour of such materials, oxidation state, geometric and electronic structure data, X-ray methods available at ESRF were used to understand the local electronic structure (determined by EXAFS) and the chemical state (from XANES).
In addition, samples with Pu content typical of corium formed from a melted
MOX fuel was analysed in a similar manner.
In summary a total of 16 samples were measured over 4 days shift.
compositions included: 3xUO2 reference, melted under argon and in air;
3x U(0.5)Zr(0.5)O2 reference, melted under argon and in air; 3x U(0.2)Zr(0.8)O2 reference, melted under argon and in air; 2x U(0.6)Zr(0.4)O2 reference and melted in air; 2x U(0.8)Zr(0.2)O2 reference and melted in air; 3xU(0.44)Pu(0.08)Zr(0.48)O2 reference, melted under argon and in air.
For all samples Zr K and U L edge data were collected.

 

Short description of the work
In the context of studies concerning the long term behaviour of nuclear glasses and in order to understand the influence of radioactivity on the glass leaching especially on the residual rate step, two different R7T7-type borosilicate glasses with a different alpha dose rate were leached in the shielded line C19 in ATALANTE facility. Solution analyses showed a drop in the alteration tracer releases indicating the formation of a protective alteration layer at the solid - solution interface. The current project objective was to better understand the nature and the morphology of this protective alteration layer formed on the radioactive glass surfaces, particularly concerning the behaviour of radionucleides, by analysing radioactive glass powders previously leached by transmission electron microscopy and secondary electron microscopy.
The two different samples of altered doped glasses have been sent to ITU for solid characterizations. The TEM grids have been prepared by grounding the glass powders into very thin fractions. For both glasses, we were able to observe the different parts of the alteration layers by TEM: alteration gel and phyllosilicates. Their quantities were different from one glass to the other one. Some black "grains" have also been observed on the most doped sample leached, and seem to be enriched in rare earth elements. Some complementary TEM and SEM characterizations are now needed to complete these observations

 
More Articles...