Development and Validation of a Flowsheet Simulation Model for Neptunium Extraction in an Advanced PUREX Process

Abstract

An Advanced PUREX process has been developed for separation and recycling of neptunium from spent nuclear fuel. This work presents a new flowsheet simulation model for the extraction of neptunium using centrifugal contactors, where mass transfer is modeled using two-film theory and a linear driving force. Distribution coefficients and neptunium redox reactions are modeled using published models. Mass transfer between the organic and aqueous phases in the phase separation zone is shown to have a negligible effect. The model is applied to a previously tested flowsheet and its predictions are shown to be in good agreement with the experimental results.

Simulation of Neptunium Extraction in an Advanced PUREX Process—Model Improvement

“…The Advanced PUREX flowsheet for neptunium co-extraction with uranium and plutonium reported by Taylor et al [11] and modeled by ourselves [13] is illustrated in Fig. 1.…”

“…In the previous work [13] , we applied the reaction kinetic model of Koltunov [18] for the redox reaction equation (1). The current work replaces this kinetics model with expressions for the forward and reverse neptunium redox reaction kinetics as shown in Eqs.…”

“…In a previous work, [13] a process model for the flowsheet simulation of an advanced PUREX process [11] was developed and implemented in gPROMS which is a software environment allowing users to build, validate, and execute steady-state and dynamic process models. [14] In this simulation code, the choice of rate equations for neptunium redox reactions has an important effect on the outcome of the model.…”

“…In this work, a more accurate model of nitrous acid distribution coefficients (also known as distribution ratios) replaces the simple method of Uchiyama [23] used in our previous work. [13] Due to the influence of nitrous acid on the redox reaction, nitrous acid generated by radiolysis of nitric acid [24] also needs to be considered in flowsheet simulation of spent nuclear fuel re-processing. Therefore, a new model for calculating radiolytic nitrous acid production was integrated into the simulation of neptunium extraction.…”

Flowsheet Simulation of Cobalt–Nickel Separation by Solvent Extraction with Trihexyl(tetradecyl)phosphonium Chloride

“…The mass transfer model is based on a linear driving force model, as these are widely used in solvent extraction process models. [57][58][59] The rate of mass transfer between the aqueous phase and ionic liquid phase can be expressed as:…”