JRP CALL information
Supported By

European Commission

Short description of the work
In the context of developing U-Pu-O type nuclear fuels with high contents of plutonium for the IVth generation nuclear reactors, much work is needed to provide the necessary accurate experimental data on the aforementioned ternary. The described project is devoted to developing a better understanding of the phases present in the UO2-PuO2-U3O8 region
We studied samples with three Pu contents (Pu/U+Pu): 14, 24 and 35 wt%. Prior to XAS experiments performed at the ESRF ROBL line in-situ high temperature X-ray diffraction has been performed at the LEFCA facility in CEA Cadarache, to achieve a certain oxygen to metal ratio (O/M). This was done by heating a stoichiometric powdered samples in air, and then reducing it at an elevated temperature using a solid state electrolyte oxygen pump, which allows for precise control of the oxygen partial pressure within the sample chamber. This way we were able to prepare samples with three different O/M ratios – O/M=2.00, O/M~2.25 and O/M corresponding to the maximum oxidation in air at 1300°C (max air). The O/M of ~2.25 was achieved by reducing the samples from the highest O/M, to a point at which all the high-oxygen hexagonal phase disappeared, leaving only a cubic M4O9 type phase, which does not exhibit strong departures from stoichiometry.

 

The six samples brought to ESRF for the experiment were: MOX with 14% Pu and O/M=2.00, 2.25 and max air; MOX with 24% Pu and O/M=2.25 and max air; MOX with 35% Pu and O/M=2.25. For the interpretation of results we will be also using spectra obtained earlier for MOX with 24 and 35% Pu and O/M=2.00. Five types of spectra were recorded for each sample UL3, PuL3, UL2, PuL2 and AmL2. All spectra were taken at room temperature to maximize the amount of acquired data with the use of an automatic sample changer.

 

From a preliminary analysis of the results it was concluded that the impact of O/M on the XANES part of the spectra is evident. After an in-depth analysis of the results we hope that it will be possible to determine the charge state and local structure around the cations in the high oxygen M4O9 and M3O8 phases. We also hope to make a comparison between the local environments of U and Pu. Finally we hope to study the nature of defects formed during oxidation, in particular the oxygen interstitial clusters.

Main visitor contact data
Name: Michal Strach
Organisation: CEA Cadarache

JRP Identification
JRP nr: TALI-C02-06
JRP title: EXAFS/XANES experiments for studying the hyper‐stoichiometric phases in the U‐Pu‐O system
JRP scope: Scope 3: Actinide materials

Visited Associated Pooled Facility
Visited APF during the stay: HZDR - ROBL
Name of the APF Contact Person: Andreas Scheinost

Other APF and organisation involved in the JRP
Other organisations involved: CEA Cadarache, LEFCA laboratory, LMPC
Other APF involved in the project:

Description of the work done at the associated pooled facility
Start date of the stay: 7/2/2014
End date of the stay: 7/5/2014
Quantity of access: 3
Access Unit: Days
Misc.:

Other APF visitors of the JRP during the stay
Visitor 2: Dr. Philippe Martin (CEA Cadarache)
Visitor 3:
Visitor 4:
Visitor 5: