Nitric Acid → HCID 20465779, compound

Participants

Reaction Steps

To demonstrate the feasibility of preparing U3O8 having a controlled particle size distribution, an exemplary feed solution (85 ml) was prepared of uranyl nitrate having a concentration of 250 gU/l at 2 M HNO3. Feed solution was contacted in suitable denitration apparatus with 70 ml of 19.9 M formic acid at a feed rate of 0.70 moles formic acid/(min)(liter of uranyl nitrate feed) solution at a temperature of 90° C. Sufficient formic acid was added to achieve a concentration of 0.3 moles /100 grams of solution at the completion of denitration. The solution was digested for one hour after completion of the formic acid addition to assure complete denitration and formation of an unsaturated solution of uranyl formate. An additional 365 ml of 19.9 M formic acid was added to the unsaturated uranyl formate solution at a feed rate of 1.27 moles/(min)(liter of uranyl nitrate feed) at 90° C. to precipitate uranyl formate monohydrate. To maximize uranium precipitation the formic acid was added until the solution acid concentration reached 1.4 moles/100 g of solution. The solution was evaporated to reduce the solution volume by 60% and adjusted with 75 ml of 90% formic acid. The slurry was cooled to ambient temperature and the precipitate recovered by filtration at a formic acid concentration of 1.7 moles/100 g solution. The precipitate was washed with 90% formic acid and the resulting filter cake was dried at 110° C. for 2 hours to provide crystalline uranyl formate monohydrate salt. This salt was then calcined in a static bed in an air atmosphere at 800° C. for 6 hours. The resulting product was a crystalline free-flowing U3O8 powder having the particle size distribution shown in the FIGURE of the attached drawing.

Provenance & Evidence