Synthesis and characterization of ceramic samarium-phosphate and samarium-phosphosilicate phases for the immobilization of actinides

 

One of the central tasks of nuclear waste disposal is the immobilization of actinides (U, Th and others) from spent fuel elements. Phosphate ceramics with a monazite structure, among other things, are excellently suited for immobilization, since such phases are able to take up larger amounts of actinides in regular positions in their crystal structures and to bind them there permanently. Natural monazite, with an age of up to 3.2 billion years, contains up to 27 percent by weight UO2 and ThO2 without showing any significant radiation damage. For this and other reasons, ceramic monazite phases are potential candidates for future disposal strategies.

The aim of this project was the synthesis of ceramic Sm-phosphate and Sm-phosphosilicate phases with monazite structure, while preserving the positive immobilization properties of monazite as completely as possible, combined with the optimization of individual properties of the ceramics (lowering of melting and sintering temperatures, etc.) as well as verification of the suitability of these phases for use in nuclear waste management. As part of the project, previously unknown phase relationships relevant to the project in the binary systems Sm2O3-P2O5, Sm2O3-Ce2O3, (Th,U)O2-P2O5 and (Th,U)O2-SiO2, in the ternary system Sm2O3-P2O5-SiO2 and in the pseudo-ternary system (Sm2O3-(Th,U)O2)-P2O5-SiO2. To answer the open questions, extensive structural analyzes should be carried out on non-irradiated and irradiated samples and the chemical resistance of the phases should be checked.

Team:

PD Dr. Hartmut Schlenz, Nukleare Entsorgung und Reaktorsicherheit (IEK-6), FZ Jülich) (Project manager)
Prof. Dr. Georg Roth (IfK, RWTH Aachen) (Project manager)
Dr. Andreas Neumann (Project scientist)

  Copyright: © DFG/JARA

Funding:

Deutsche Forschungsgemeinschaft (DFG)
Cooperation with JARA|ENERGY
Grant Nr.: RO 2055/7-1
Project period: 01.07.2012 – 30.06.2015