Fluorine plays an essential role in the nuclear fuel cycle: it is an indispensable component in the preparation of UF6 used in the uranium enrichment process in nuclear power plants. Fluorine is produced by electrolysis of the molten salt KF-2 HF on the non-graphite carbon anode between 85°C and 100°C. The reduction reaction that takes place at the cathode produces hydrogen. An electrolysis cell consists of covers, cooling coils, diaphragm made of nickel alloy (67%) and copper (28 to 30%). This alloy has a remarkable resistance to corrosion. Increasing effectiveness and reliability of the electrolyzer need to change paradigms such as materials and manufacturing’s processes.
It is therefore envisaged to replace this material by a high performance ceramic, silicon carbide, in order to develop new diaphragms with more complex geometries to improve gas separation.
The objective of the thesis will be to study the performance of a SiC-based material, printed by additive manufacturing and sintered in order to obtain parts with high densities (70-90%) and low oxygen content to be compatible with HF electrolysis.
An in-depth analysis will be undertaken by IGA/ICP, SEM-MET/EDX on SiC materials developed and shaped by flash sintering (screening) in order to relate the nature of SiC, the density and the location of oxygen. A second step will focus on the shaping by 3D printing of the selected material followed by thermal sintering treatments with the technological challenge of obtaining high density parts. The performances of these simple and complex parts will be evaluated in HF environment and under fluorine bubbling. These implementations will be followed by characterizations in order to establish relationships between the properties of the material obtained by 3D printing (its microstructure, its density, the presence of oxygen) and its performances.