Dissolution Kinetics of U₃Si₂ Particles in Alkaline Hydrogen Peroxide

Nonproliferation concerns leading to the conversion from high- to low-enriched uranium sparked interest in U₃Si₂ dispersion targets as an option for ⁹⁹Mo production. Dissolution of irradiated targets is an important step in recovering fission-product ⁹⁹Mo. Alkaline hydrogen peroxide solutions dissolved U₃Si₂ particles in an open batch reactor; samples were analyzed for total peroxide and uranium concentrations as functions of time and temperature. Dissolution rates are highest at 1 to 1.5 M NaOH and change little for initial base concentrations from 0.5 to 2.5 M NaOH, indicating relatively robust process conditions. Uranium dissolution rates depend most strongly on the equilibrium concentration of the peroxyl ion (O₂H⁻), an equilibrium product of hydrogen peroxide (H₂O₂) and hydroxyl ion (OH⁻). Temperature and equilibrium concentrations of O₂H⁻ and OH⁻ are included in a uranium dissolution rate model.