Optimization of process parameters in precipitation for consistent quality UO2 powder production

Abstract

Nuclear reactor grade natural uranium dioxide powder is being produced through precipitation route, which is further processed before converting into sintered pellets used in the fabrication of PHWR fuel assemblies of 220 and 540 MWe type reactors. The process of precipitating Uranyl Nitrate Pure Solution (UNPS) is an important step in the UO₂ powder production line, where in soluble uranium is transformed into solid form of ammonium uranate (AU), which in turn reflects and decides the powder characteristics. Precipitation of UNPS with vapour ammonia is being carried out in semi batch process and process parameters like ammonia flow rate, temperature, concentration of UNPS and free acidity of UNPS are very critical and decides the UO₂ powder quality. Variation in these critical parameters influences powder characteristics, which in turn influences the sinterability of UO₂ powder. In order to get consistent powder quality and sinterability all the critical parameters of precipitation are studied, optimized and validated. The critical process parameters are controlled through PLC based automated on-line data acquisition systems for achieving consistent powder quality with increased recovery and production. The present paper covers optimization of process parameters and powder characteristics.