Electrochemical behavior of iodide ions in molten fluoride salts

International audienceThe electrochemical behavior of iodide ions has been studied in the ternary fluoride salt, LiF-NaF-KF and in the binary salts, LiF-CaF2 and LiF-ThF4. The electrochemical study demonstrated that iodide ions are oxidized to produce gaseous species in the three molten fluoride salts. However, the stability of iodide ions was observed to be influenced by the fluroacidity of the molten salt. The efficiency of the extraction of iodide ions was examined in LiF-NaF-KF and LiF-ThF4. UV-visible spectroscopy was used to quantify the amount of iodide ions oxidized after the execution of several coulometries at applied potential, these coulometries simulated the fluorination step in the reprocessing unit designed for the MSFR. The efficiency of extraction determined in LiF-ThF4 is higher than 95 % while it is close to 64 % in LiF-NaF-KF at 650°

Pyrochemical reprocessing of molten salt fast reactor fuel: focus on the reductive extraction step

The nuclear fuel reprocessing is a prerequisite for nuclear energy to be a clean and sustainable energy. In the case of the molten salt reactor containing a liquid fuel, pyrometallurgical way is an obvious way. The method for treatment of the liquid fuel is divided into two parts. In-situ injection of helium gas into the fuel leads to extract the gaseous fission products and a part of the noble metals. The second part of the reprocessing is performed by ‘batch’. It aims to recover the fissile material and to separate the minor actinides from fission products. The reprocessing involves several chemical steps based on redox and acido-basic properties of the various elements contained in the fuel salt. One challenge is to perform a selective extraction of actinides and lanthanides in spent liquid fuel. Extraction of actinides and lanthanides are successively performed by a reductive extraction in liquid bismuth pool containing metallic lithium as a reductive reagent. The objective of this paper is to give a description of the several steps of the reprocessing retained for the molten salt fast reactor (MSFR) concept and to present the initial results obtained for the reductive extraction experiments realized in static conditions by contacting LiF-ThF4-UF4-NdF3 with a lab-made Bi-Li pool and for which extraction efficiencies of 0.7% for neodymium and 14.0% for uranium were measured. It was concluded that in static conditions, the extraction is governed by a kinetic limitation and not by the thermodynamic equilibrium