Quantitative Raman Investigation Of Uranyl Sulfate Complexation Under Hydrothermal Conditions

Abstract

Quantitative data for the first and second formation constants of aqueous uranyl sulfate complexes were obtained from Raman spectra of solutions at temperatures ranging from 25 - 375 °C and at 25 MPa. Temperature-dependent values of the O=U=O vibrational frequencies of UO₂²⁺(aq), UO₂SO₄⁰(aq) and UO₂(SO₄)₂^2-(aq) were derived from high temperature spectra and used to determine the formation constants. Results will be used in the EPRI software package MultEQ and other chemical equilibrium modelling programs to calculate U(VI) fuel failure chemistry under current CANDU-6 conditions and those proposed for the SCWR.