The Acid Thorex process has been developed on a laboratory scale for recovery of uranium and thorium from spent fuel solutions. The thorium and uranium are extracted by tributyl phosphate (TBP) with only the thorium nitrate and nitric acid as “salting agents.” As compared to the present Thorex process in which aluminum nitrate is employed as a salting agent, a considerably greater reduction in aqueous waste volumes is possible. With a synthetic solution of Consolidated Edison Thorium Reactor fuel as feed, uranium and thorium were decontaminated from ruthenium, zirconium-niobium, protactinium, and rare earth elements by factors of 2,000, 30,000, 1,000, and 105, respectively. The concentrated aqueous waste volume was 0.2 liter per kilogram of thorium processed. These values compare favorably with corresponding decontamination factor values for the aluminum-salted Thorex system of 600, 3,000, 3,000, and 2 × 105 and volume of 2 liters per kilogram of thorium processed.