R. Jardin

Electrorefining of U-Pu-Zr-alloy fuel onto solid Aluminium cathodes in molten LiCl-KCl

An electrorefining process in molten chloride salts using solid aluminium cathodes is being developed at ITU to recover actinides (An) from the spent nuclear fuel. The maximum possible loading of aluminium electrodes with actinides was investigated during the electrorefining of U-Pu-Zr alloy in a LiCl-KCl eutectic at 450 °C. Two different electrolytic techniques were applied during the experiment and almost 6000 C has been passed, corresponding to 3.7 g of deposited actinides. A very high capacity of aluminium to retain actinides has been proven as the average Al: An mass ratio was 1:1.58 for galvanostatic and 1:2.25 for potentiostatic mode. The obtained deposits were characterized by XRD and SEM-EDX analysis and alloys composed of (U,Pu)Al3 were detected. The influence of zirconium co-oxidation during the process was also investigated and the presence of dissolved Zr ions in the melt yielded a significant deterioration of the quality of the deposit.

Tin flux synthesis of rare-earth metal silicide compounds RESi1.7 (RE = Dy, Ho) : a novel ordered structure derived from the AlB2 type

Abstract The binary rare-earth metal silicides RESi1.7 (RE = Dy, Ho) were prepared by tin flux synthesis between 800–1000 °C. Single crystals were obtained after electrochemical dissolving of molten ingots. Their crystal structures were determined from single-crystal X-ray data: orthorhombic symmetry, space group Imm2; unit cell parameters a = 19.144(1), b = 8.2562(3), c = 6.6571(3) Å and a = 19.063(1), b = 8.2120(2), c = 6.6313(2) Å for DySi1.7 and HoSi1.7, respectively. They represent a new ordered structure type, which is a derivative of the defect AlB2 type. The main structural feature is the occurrence of a vacancy ordering in the two-dimensional planar network of silicon atoms, leading to rows of edge-shared twelve-membered rings separated by distorted hexagonal rings. Structural comparison with the parent hexagonal silicide Yb3Si5 (Th3Pd5 type), the structure of which has been re-determined on single crystal, is also given.