Integrated model development for safeguarding pyroprocessing facility: Part I-model development and validation

Pyroprocessing is a method involving electrochemistry, thermodynamics, and transport theory. Driven by the current, nuclear materials redistribute between anode, electrolyte, and cathode to realize the desired separation. In the present study, a model for predicting the mass transport for the electrochemical process was developed. The model took into account the following key parameters: diffusion and mass transfer in both the electrode and electrolyte, the anodic dissolution and cathodic precipitation kinetics, the molten salt flow condition, and the solubility of species in molten LiCl-KCl and liquid cadmium. It was validated by available transport data between different pairs of the electrodes, namely liquid cadmium anode to solid cathode, solid anode to solid cathode, and solid anode to liquid cadmium cathode. Time for Pu depositing on the solid cathode as well as Zr dissolving from U-Pu-Zr alloy anode was precisely predicted. The potential and composition changes in various experiments were also well reproduced. The plausible explanation was given to explain the minor disagreement and future work was suggested to improve its capability. The model is useful to understand the reaction mechanisms and safeguard a pyroprocessing facility by monitoring the separation process and tracking the material flow.