Electrochemical measurements (potential monitoring, impedance measurement and slow cyclic voltammetry) have been used to monitor the surface reactions of spent fuel under storage conditions. The analysis was aided by equivalent circuit modelling of the interface. The potential of the spent fuel rose rapidly at first, and then more slowly, reaching domains of oxidative dissolution. The sharp potential drops observed were shown by the impedance modelling to be due to cracking in the fuel to the electrode base. The corrosion rates ranged from 0.03–0.2 mg/(m2.d) and were similiar with those estimated by a potential correlation method.