Electrochemical and Surface Analysis of Hydrogen Effects on Uranium Dioxide

Abstract

Electrochemical and X-ray photoelectron spectroscopic (XPS) techniques were used to investigate the effect of hydrogen on the aqueous corrosion of SIMFUEL (UOB 2B) electrodes with different degrees of simulated burn-up under nuclear waste disposal conditions. Corrosion potential measurements (EB CORRB) showed that as fuel burn-up increased, EB CORRB in 5% HB 2B/95% Ar decreased. XPS, performed after EB CORRB measurements, showed the surface film composition as a function of the purge gas used (Ar or 5% HB 2B/95% Ar). The uranium (4fB 7/2B) peak was resolved into contributions from UP IVP, UP VP , and UP VIP . When purged with HB 2B, the film composition is mainly UP IVP , meaning very little oxidation to UP VP and/or UP VIP has occurred. This suppression of oxidation can be attributed to the presence of ε-particles in the SIMFUEL since experiments on SIMFUEL samples with no ε-particles showed a lower percentage of UP IVP and higher percentages of UP VP and UP VIP , due to more extensive surface oxidation. Consistent with this observation, EB CORRB on the SIMFUEL containing no ε-particles was 150 mV more positive than values recorded on the SIMFUEL with ε-particles.