?Integration of Simulated Electrochemistry Data into a General Pyroprocessing ?Mass Accountancy Model for Signature Based Safeguards

Growing interest in electrochemical reprocessing of used nuclear fuel (UNF) necessitates development of an accurate and precise mass accountancy model incorporating process monitoring (PM) methods. Current mass accountancy models for safeguards purposes are based on assumptions regarding transport within the electrorefiner, without using any fundamentals of electrochemistry for the modeling of the electrorefiner subsystem where the active products (uranium, plutonium, minor actinides, etc.) are separated from UNF for the formation of the final metallic ingot produced during cathode processing. Previous studies in PM involved using ERAD, a computational one dimensional electrorefiner model, and an MCNP model of Canberra’s High Level Neutron Coincidence Counter (HLNCC). The studies in ERAD demonstrated which off-normal conditions make codeposition of plutonium and uranium possible. The studies with the HLNCC determined the detector response for both singles and doubles counts for various levels of plutonium deposition in the final ingot produced from the electrorefiner. These studies are expanded to include further off-normal conditions and ultimately integrated into a systems model for the entire pyroprocess. The aim of this research is to implement fundamental electrochemistry simulations and observed HLNCC predictions for the electrorefiner product into a pyroprocessing systems model. To do so, calculations were performed in ERAD and MCNP, and results for various modes of electrorefiner operation were attained. These results were then integrated into a systems model Echem in the form of functions and tables. For this work, the effect of fluctuations in diffusion layer thickness, current density, and surface area of the cathode on the overall mass balance of the system was investigated. These calculations give insight on what additional parameters need to be monitored, and to what extent, in order to facilitate a high probability of detection. The integration of the parameters within the model also facilitates the understanding on how they can affect the overall performance of a commercial pyroprocessing facility. This paper presents an additional step towards having an accurate pyroprocessing system model, which uses fundamental electrochemistry calculations to safeguard an electrochemical reprocessing facility.