Uranium Oxides*

Since the advent of nuclear technology, the dissolution behavior of uranium oxides has been a matter of great practical importance in all stages of fuel production. In extractive metallurgy of uranium ores, acid and alkaline leaching in the presence of O₂ and carbonate are procedures of widespread use. This chapter discusses that oxidative dissolution assisted by carbonate complexation of UO₂⁺ is probably the most practical way to dissolve UO₂. This oxide constitutes the basis of two common minerals, pichtblende and uraninite. Uranium mining raises concern about the possible contamination of aquatic systems by mine tailings and wastes; sound management therefore requires an adequate understanding of the mobilization of uranium, a process mediated by dissolution in mildly oxidic conditions. Oxidative dissolution is potentially a major source of error in the experimental attempts to measure the solubility of UO₂ as a U(IV) concentration value.