Spectrophotometry of Aqueous Homogeneous Reactor Fuel Solutions from 4 to 280°C and 0 to 930 psi(abs)

Aqueous homogeneous reactor fuel solutions have been examined spectrophotometrically in the wavelength range 0.3 to 1.2µ as a function of time, temperature, and overpressures of hydrogen and/or oxygen. Using a cell that was designed for liquid-gas equilibration, and which were slightly catalytic for the recombination of hydrogen and oxygen, the course of reactions (reduction, hydrolysis, precipitation, oxidation, and re-solution) of uranium and copper were followed concomitantly. Degassed solutions of the UO₂SO₄-CuSO₄-D₂SO₄-D₂ O-H₂O system lost uranium and copper very slowly above 200°C. In the presence of hydrogen, Cu(II) and U(VI) were reduced consecutively to Cu (metal) and to U(IV) species that were partially soluble at 25°C, but insoluble above 150 to 200°C. The changing spectrum was generally uncomplicated by turbidity, since reduction of Cu(II), as well as aggregation of U(IV) hydrolytic species, occurred at the cell wall. Hydrolysis of U(IV) was slowly reversible with decreasing temperature. Reoxidation of reduced solution with oxygen was comparatively rapid and complete at all temperatures.