A computer model of an air-lift dissolver was developed to predict the dissolution rates for plutonium oxide (PuO2), dysprosium oxide (Dy2O3), and incinerator ash. This model combines surface kinetics with mass transfer effects to obtain overall rate expressions. The mass transfer coefficients are related to several major process variables. These predictions were compared with experimental tests at Savannah River Laboratory using simulated ash and Dy2O3 as a surrogate for refractory PuO2. The present version of the model overestimates the residual fluoride concentrations in dissolver effluents by ∼50% for several reasons, which are discussed. The minimum air sparge rates to achieve liquid circulation in the dissolver are predicted quite well, within ± 6%. The nonvolatile dissolved solids are estimated to within ±5 to 20%. Dysprosium dissolution is predicted to within ±10%. Dysprosium oxide is a poor surrogate for refractory PuO2.