Studies on the Radionuclide Coprecipitation-Solid Solution Formation. The UO2(S)-La(OH)3(S) Coprecipitation as an Analogue for The UO2(S)-Pu(OH)3(S) System

Abstract

AbstractThe UO2(s)-La(OH)3(s) coprecipitation equilibria have been studied in 0.5 M NaClO4 medium, at 25°C under anoxic conditions. The data obtained in the pH range between 2 and 5, and at different initial La(III)/U(IV) ratios (10%,5%,3%,2% and 1%), is explained by applying the Doerner-Hoskins logarithmic law. The same law can also be used to describe previously collected UO2(s)-Pu(OH)3(s) coprecipitation data. A method is proposed which uses the logarithmic distribution constants and the thermodynamic quantities for the pure phases to describe the solubility of radionuclides under repository conditions.