Process for making high quality nuclear fuel grade ammonium diuranate from uranyl fluoride solutions

A continuous process is disclosed for precipitating uranium from an aqueous solution formed by the hydrolysis of uranium hexafluoride gas. Undersized ammonium diuranate particles are formed in a first container by mixing the aqueous solution and an ammonium hydroxide solution containing about 10 to about 30% by weight ammonium. The ratio of the two solutions should be such that there are about 20 to 30 moles of ammonium per mole of uranium. The temperature is maintained at about 300 to about 500C. and the residence time in the first container is about 14 to about 57 seconds. The slurry is then transported to a second container for further particle growth where it is agitated at a temperature of about 200 to 400C. for a residence time of about 2 to about 9 minutes. The resulting ammonium diuranate precipitate has a surface area of about 10 to about 20 meters squared per gram. The precipitate can then be calcined and pressed into pellets