Modeling the Distribution of Acidity within Nuclear Fuel (UO2) Corrosion Product Deposits and Porous Sites

A model for acidity within pores within corrosion products on anodically-dissolving UO2 was developed using Comsol Multiphysics 3.2 to complement ongoing electrochemical measurements. It was determined that a depression of pH within pores can be maintained if: electrochemically measured dissolution currents used in the calculations are attenuated to reflect very localized pores; corrosion potentials exceed -250 mV (vs. SCE); and pore depths are >1 μm for 300 mV or >100 μm for -50 mV (vs. SCE). Mixed diffusional-chemical equilibria control is suggested through deviations in the shapes between pH-potential and pH-pore depth plots. (authors)