An Integral Approach for Handling and Minimizing Effluent Generation During Production of Sinterable Grade UO₂ Powder for PHWR Fuels

Abstract

Nuclear reactor grade natural uranium dioxide powder is being produced through Ex-AU route, which is further processed to manufacture UO₂ pellets by sintering process for making PHWR fuel assemblies. During UO₂ powder production, Ammonium Nitrate (AN) is a liquid effluent which is produced with different concentration at two process steps namely: a) Vapour ammonia neutralization of Uranyl nitrate raffinate (UNR), generated from slurry extractor b) Vapour ammonia precipitation of Uranyl Nitrate Pure Solution(UNPS). This effluent is checked for AN concentration and Uranium activity for subsequent treatment before safe disposal. The AN concentration is on lower side for the effluent generated during vapour ammonia precipitation of UNPS, making it difficult for disposal. An integrated approach was developed for resolving the disposal related problems because of different grade of AN effluents. In the proposed method, the low grade AN effluent is processed using UNR, generated during slurry extraction. For increasing the AN concentration, this process was standardized by optimizing parameters like UNR to AN ratio, pH, ammonia flow rate, temperature etc. This development has resulted in adjusting the AN concentration among the effluents there by reduction in the acid and ammonia chemical consumption, effluent quantity and paved the way for optimization of process flow sheet for safe disposal.