Electromotive force measurements of U-Zr alloys in LiCl-KCl-UCl3 melt

Abstract

Electromotive force measurements of U-60Zr (79.6 at.% Zr) and U-77Zr (89.7 at.% Zr) alloys in LiCl-KCl-UCl₃ melt were carried out in temperature range 670-800 K for determining ${\Delta }_{\text{f}}{G}_{{\mathrm{UZr}}_2}^{\circ }$, the temperature dependence of which was expressed as

${\Delta }_{\text{f}}{G}_{{\mathrm{UZr}}_2}^{\circ }$ $\left(\text{kJ/mol-atom}\right)=(-59.29\pm 1.37)+(32.0\pm 1.9)\times 10^{-3}T\left(\text{K}\right)$

Correlation suggested stability of $\delta$-UZr₂ to be higher than what is currently accepted in literature, which is based on its enthalpy of formation at 298.15 K. Cyclic voltammetry with U-Zr alloys as working electrode was also performed in potential range −1.50 to −0.50 V in LiCl-KCl-UCl₃ melt for exploring onset potential of dissolution of uranium and zirconium to address consequences of higher stability of UZr₂ on spent metal fuel dissolution.