Annual Report 2009/2010 - JUWEL - Forschungszentrum Jülich

actinide co-conversion into polyactinide solids (structural studies) to deeply understand and
improve the co-conversion process.
In a complementary partitioning & conditioning strategy (P&C), new nuclear waste forms
such as ceramic matrices with high radiation resistance and aqueous durability are of interest
for the safe disposal. At present, high-active waste is generally vitrified. Ceramic matrices are
much more stable and therefore form a final disposal product which can effectively prevent
radionuclides escaping from the repository for extremely long periods of time.
P&C may help to reduce the actinide source term from a repository in case of water access.
Due to their advantageous properties zirconia based compounds and monazite are
considered within the R&D programme of the IEK-6.
Contact:
Dr. Giuseppe Modolo
g.modolo@fz-juelich.de
3.3.
Structure Research
The chemical and physical properties of a material are determined by its chemical
composition, present chemical bonds and particularly by its structure, no matter if crystalline
or amorphous materials (glasses) are investigated. According to nuclear waste management
mainly ceramics and glasses are considered for the immobilization of actinides. For the
purpose of understanding material properties and for the development of such new materials,
knowing the structure is an indispensable prerequisite. As an example the crystal structure of
the mineral monazite (Fig. 5, left) is determined as a function of varying amounts of Uranium
(U) and Thorium (Th) using x-ray powder diffraction, in order to detect structural changes due
to varying chemical composition and possible radiation damage caused by the radioactive
decay of U and Th. Further candidate phases for the immobilization of actinides are e.g.
pyrochlore, Ce-, U- and Th-oxides, as well as U- and Th-silicates.
Fig. 5: Left: Crystal structure of the mineral monazite. Right: powder diffractogram of a LaB 6
standard.
At the IEK-6 structure research is performed using diffraction (Fig. 5, right) and spectroscopic
analysis. X-ray synchrotron diffraction and spectroscopy experiments are performed at large
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