Development of an efficient 1-dimensional computer code to model mass transport and separation in electrorefining, a key component process of pyroprocessing, is described in this paper. A variety of phenomena occurring in electrochemical devices is reviewed along with examination of existing computer models to provide basis for new model development. Key processes and phenomena of importance were selected based on describing rate-limiting steps and separation efficiency of electrorefining. The developed model, named ERAD, describes time-dependent behavior of multi-component electrochemical systems with the capability of depicting anodic dissolution of spent nuclear fuel, non-hydrodynamic mass transport effects in the electrolyte, and cathodic deposition of materials. Utilization of the model is demonstrated through comparison with existing experimental data. For the purpose of model validation, model predictions are also compared with cyclic voltammetry and other experimental data.