The Electrolytic Reduction of Gd₂O₃ in LiCl-KCl-Li₂O Molten Salt

Abstract

In the common spent fuels, actinides and fission products are generally in the form of oxide, so direct dealing with oxide will be the most convenient way for spent fuel reprocessing. In this work, the electrolytic reduction of Gd2O3 has been studied in LiCl-KCl-Li2O (1 wt%) melts at different conditions, and the effect of sintering temperature on the porosity of Gd2O3 powder and the electrochemical behavior of Li2O in LiCl-KCl molten salt were investigated, too. The diffusion coefficient of O2− was calculated to be 2.0 × 10−5 cm2·s−1 in LiCl-KCl melts on the Mo electrode at 923 K by cyclic voltammetry (CV). The electrode process of Gd2O3 powder was also analyzed in LiCl-KCl-Li2O (1 wt%) melts, and the formation process of composite oxide LiGdO2 was determined. By the analysis of XRD and oxygen content characterization, it was suggested that after 74 h electrolysis (923 K, 3.40 V), the oxygen content of Gd2O3 cathode decreased from 12.25 wt% to 1.41 wt%, indicating 88.5% Gd2O3 was reduced to metal.

The Electrolytic Reduction of MoO3 in CaCl2-NaCl Molten Salt

“…The theoretical value of oxygen content of MoO 3 is 33.34%, and therefore, the reduction ratio (ε r ) of MoO 3 can be calculated according to Eq. 9 25 :…”

“…5,[10][11][12][13][14][15][16] At present, the research of electro-deoxidation in molten salt mainly focused on transition metal oxides such as TiO 2 , 12,17 ZrO 2 , 18 HfO 2 , 19 Nb 2 O 5 , 20 Ta 2 O 5 , 21 Cr 2 O 3 22 and NiO 23 and so on. Rare earth oxides, including CeO 2 , 24 Gd 2 O 3 , 25 Tb 4 O 7 26 and Dy 2 O 3 27 etc., were also investigated. In actinides, the studies were mainly conducted on uranium oxides, such as UO 2 28,29 and U 3 O 8 .…”

Electrolytic reduction of Gd2O3-ZnO in NaCl-CaCl2 Molten Salt

“…6. 35 In contrast, at a terminal potential of −2.30 V, the intensity of peak B' decreased obviously, indicating the decrease of reduction products. The negative shift of terminal potential in the CV scan would lead to the deposition of Na on the electrode and the subsequent addition of reduction products in Eq.…”

Electrical Conductivity of GdCl3-Gd2O3 Molten System

“…6,7 The direct electro-reduction of Gd 2 O 3 in LiCl-KCl-Li 2 O (1 wt %) melt is a feasible method to obtain Gd metal, which can be proposed for preparing other RE metals. 8 RE oxides can be dissolved in chloride melts and oxides solubility increases with an increase of the concentration of the corresponding RE chlorides in the melt. For example, as has been shown earlier the solubility of gadolinium oxide in molten GdCl 3 can achieve 8.2 mol % at 880 K. 9 Electrical conductivity is one of the most investigated properties of molten salts.…”