The solubility of UO22+ in dilute sodium chloride solutions and in high-ionic strength sodium sulfate and chlorine brines

Uranium is a major component of high-level nuclear waste. In an oxidizing environment, UO22+ would be expected to be the dominant dissolved species in solution. In addition to dilute solutions, because high-level nuclear waste may be stored in repositories containing salt, it is important to characterize the aqueous chemistry of UO22+ and the solubility-controlling U(VI) solids in high-ionic strength brines as a function of pH. We have studied the solubility of UO22+ by precipitation of solid phase in 0.001 molal NaCl, 5.2 molal NaCl, and saturated Na2SO4 at pH values ranging from 5 to 12. The solution concentrations were measured by alpha particle liquid scintillation counting. The precipitated solids were characterized by powder x-ray diffraction, electron microscopy, infrared spectroscopy, and x-ray photoelectron spectroscopy