Thermochemical Evaluation of Standard Electrode Potential and Gibbs Energy of Formation of PuCl_3 in LiCl-KCl Eutectic Melt

摘要

This paper deals with the estimation of E°_(Pu~(3+)|Pu) and Δ_fG°_(PuCl_3) of the Pu3+|Pu redox couple in LiCI-KCI eutectic melt using statistical data fitting of experimental data. The E*°_(Pu~(3+)|Pu) value was also estimated in our laboratory at 723 and 773 K using logarithmic analysis of semi-integral voltammograms and chronopotentiograms. From semi-integral curves, E*°_(Pu~(3+)|Pu) was found to be —2.888 ± 0.021 and -2.810 ± 0.021 Vat 723 and 773 K, respectively, whereas it was -2.851 ± 0.020 Vat 773 K from the analysis of chronopotentiograms. Based on subsequent statistical analysis, we recommend the following expressions for E°_(Pu~(3+)|Pu) and Δ_fG°_(PuCl_3) applicable for the temperature range 673 to 823 K: E°_(Pu~(3+)|Pu) versus Cl~-|Cl_2 (V) = -(3.325 ± 0.117) + (7.212 ± 1.571) × 10~(-4)T(K) and Δ_fG°_(PuCl_3) (J/mol) = -(962738 ± 33982) + (208.8 ± 45.5)T(K). The γ_(PuCl_3) value in LiCI-KCI eutectic melt was estimated from Δ_fG°_(PuCl_3,liq) calculated for the reaction Pu(s)+(3/2)Cl_2(g)→PuCl_3 (liq.) using FactSage package, and it was expressed as