From ambient to extreme conditions: a systematic investigation of actinides chemistry in fission products based oxo-salt systems

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The knowledge of the chemical properties of actinide elements (An) and associated materials are crucial for correct spent nuclear fuel and waste form safety assessments and are of high interest for fundamental science. The actinides are 5f-elements, which possess a plethora of unique chemical (multi-valence, extremely diverse coordination chemistry) and physical (magnetic ordering, superconductivity) properties. Until now several chemical aspects of actinide science are unclear, particularly the dependence of their reactivity to variable synthetic conditions, particularly those relevant to spent nuclear fuel and repository conditions, and the further role of 5f-electrons in bonding between An centers and oxo-salt ligands. Within the research we will combine the unique expertise of German and Chinese partners to perform a systematic investigation of the early actinides, Th, U, Np, and Pu, their interaction with oxo-salt groups that are based on key fission products, for instance Se, I, Mo. We will perform this study in a wide range of synthetic conditions ranging from ambient pressure and room temperature up to 2500 °C and 25 GPa. We will study chemical and structural properties of the obtained materials with a particular emphasis on electronic structure the further relation of 5f-electrons involvement in bonding. The group of Prof. Alekseev (Jülich, Germany) will focus on solid state reactions with particular emphasis on extreme conditions of pressure and temperature. The group of Prof. Wang (Suzhou, China) will be responsible for the investigation of reactions in aqueous solutions including those involving supercritical water. As a result of this joint Sino-German project we expect considerable scientific advancement in: 1. Synthetic chemistry of the early actinides in respect to their reactivity and phase formation at various synthetic conditions from ambient to extreme pressures and temperatures;2. Structural chemistry of early actinide based oxo-materials; 3. The understanding of the bonding nature between An centers and different type of oxo-ligands.We believe that this DFG-NSFC joint project will bring our cooperation onto a new, highly effective performance level and will play a significant role in German-Chinese scientific cooperation in the field of radiochemistry.