Modelling the radiolytic corrosion of α-doped UO2 and spent nuclear fuel

Abstract A model previously developed to predict the corrosion rate of spent fuel (UO 2 ) inside a failed waste container has been adapted to simulate the rates measured on a wide range of α-doped UO 2 and spent fuel specimens. This simulation confirms the validity of the model and demonstrates that the steady-state corrosion rate is controlled by the radiolytic production of H 2 O 2 (which has been shown to be the primary oxidant driving fuel corrosion), irrespective of the reactivity of the UO 2 matrix. The model was then used to determine the consequences of corrosion inside a failed container resealed by steel corrosion products. The possible accumulation of O 2 , produced by H 2 O 2 decomposition, was found to accelerate the corrosion rate in a closed system. However, the simultaneous accumulation of radiolytic H 2 , which is activated as a reductant on the noble metal ( e ) particles in the spent fuel, rapidly overcame this acceleration leading to the eventual suppression of the corrosion rate to insignificant values. Calculations also showed that, while the radiation dose rate, the H 2 O 2 decomposition ratio, and the surface coverage of e particles all influenced the short term corrosion rate, the influence of the radiolytically produced H 2 was the overwhelming influence in reducing the rate to negligible level (i.e., −20 mol m −2 s −1 ).