Spray drying of ammonium diuranate slurries

Abstract

Slow and fast settling ammonium diuranate (ADU) slurries were dried in a one metre diameter laboratory spray drier using either pneumatic or centrifugal atomisation. Uniform, fine, dry powders were obtained with both atomisation techniques but pneumatic atomisation was preferred. Spray drying did not adversely affect the properties of the subsequent UO2 powder and pellets. It was not necessary to treat the ADU feed slurry to remove ammonium nitrate in solution. A theoretical model of droplet evaporation during spray drying is developed, taking into account droplet size distribution, gas-spray hydrodynamics and heat transfer rates. This model satisfactorily accounts for the observed operational characteristics of the drier.