Determination of the solubility product of plutonium sesquioxide in the NaCl+CaCl 2 eutectic and calculation of a potential–pO 2− diagram

Abstract

Reactions between plutonium trichloride and oxide ions were studied in the fused NaCl+CaCl 2 equimolar mixture at 823 K, by potentiometry with an yttria-stabilised zirconia membrane electrode. Titration curve demonstrated the existence of a precipitated plutonium oxide (Pu 2O 3) with dissociation constant 10 −17.5 (molality scale). The combination of this data with the standard potentials allowed to set up the potential–pO 2− diagram of plutonium which summarises the properties of plutonium species in the melt.