Generation of equilibrium data for diluent wash flowsheet development relevant to nuclear fuel reprocessing

In the PUREX process for the recovery of uranium and plutonium from spent nuclear fuel by solvent extraction employing tributylphosphate (TBP) as the solvent diluted with n-dodecane (n-DD), all the aqueous streams exiting the solvent extraction cycles are always associated with some dissolved organics. Subsequently during the evaporation of these aqueous streams for their volume reduction for better waste management, the dissolved organics pose serious safety hazards as they can lead violent runaway reactions at elevated temperatures in the presence of nitric acid which may lead to red oil explosion. Diluent wash is one of the effective methods to remove the dissolved organics from the aqueous streams. For commercial spent nuclear fuel reprocessing, it is desirable to operate this process on a continuous mode for various known advantages. The basic requirement of designing this continuous process flowsheet is the process equilibrium data. Hence experiments were carried out to generate the equilibrium data for designing a continuous diluent wash process flowsheet relevant to spent nuclear fuel reprocessing, for FBRs in particular. The data were generated in the absence of any metal ion which is very conservative to start with as presence of any of them will only lead to further reduced solubility of TBP in nitric acid stream