JRP CALL information
Supported By

European Commission

Short description of the work
The aim of the project was to investigate solubility of uranium in lanthanum zirconate (La2Zr2O7), which has been previously studied as a model system for the immobilisation of actinides. Zirconate pyrochlores are highly radiation tolerant and extremely durable making them ideal candidates for the disposal of high activity long half life wastes, including plutonium, uranium and minor actinides. This work looked at the effect of substituting uranium (as a plutonium analogue) into lanthanum zirconate, La2Zr2-xUxO7+ɣ, under different processing conditions. Oxidising and reducing atmospheres, air and H2/N2 respectively, have been used to investigate the speciation of uranium in different valence states which have been determined using X-ray absorption specrocopy (XAS).
Structural analysis has been performed using X-ray diffraction but due to the small scattering factor of oxygen the technique is in-sensitivity to oxygen vacancy ordering in these materials and hence it is difficult to observed subtle structural changes. Transmission electron microscopy (TEM) is more sensitive to cation and anion ordering and it has been demonstrated that this ordering can be determined from analysis of electron diffraction patterns. The presence / absence of sharp or diffuse scattering at key super-lattice positions enables differentiation of different structure types which appear identical by X-ray powder diffraction. It was therefore possible to determine the solubility limit of uranium and the structural modulations that occurred as a function of uranium content.

Main visitor contact data
Name: Laura Casey
Organisation: University of Sheffield

JRP Identification
JRP nr: TALI-C04-03
JRP title: The Characterisation of uranium containing
JRP scope: Scope 3: Actinide materials

Visited Associated Pooled Facility
Visited APF during the stay: JRC-ITU - Labs & Hot-cells
Name of the APF Contact Person: Thierry Wiss and Philippe Raison

Other APF and organisation involved in the JRP
Other organisations involved: University of Sheffield (Dr Martin Stennett)
Other APF involved in the project:

Description of the work done at the associated pooled facility
Start date of the stay: 2/26/2015
End date of the stay: 3/6/2015
Quantity of access: 15
Access Unit: Days

Other APF visitors of the JRP during the stay
Visitor 2: Dr Martin Stennett (University of Sheffield)