H2 inhibition of radiation induced dissolution of spent nuclear fuel

In order to elucidate the effect of noble metal clusters in spent nuclear fuel on the kinetics of radiation induced spent fuel dissolution we have used Pd particle doped UO2 pellets. The catalytic effect of Pd particles on the kinetics of radiation induced dissolution of UO2 during γ-irradiation in HCO3- containing solutions purged with N2 and H2 was studied in this work. Four pellets with Pd concentrations of 0%, 0.1%, 1% and 3% were produced to mimic spent nuclear fuel. The pellets were placed in 10 mM HCO3- aqueous solutions and γ-irradiated, and the dissolution of UO22+ was measured spectrophotometrically as a function of time. Under N2 atmosphere, 3% Pd prevent the dissolution of uranium by reduction with the radiolytically produced H2, while the other pellets show a rate of dissolution of around 1.6 × 10−9 mol m−2 s−1. Under H2 atmosphere already 0.1% Pd effectively prevents the dissolution of uranium, while the rate of dissolution for the pellet without Pd is 1.4 × 10−9 mol m−2 s−1. It is also shown in experiments without radiation in aqueous solutions containing H2O2 and O2 that ϵ-particles catalyze the oxidation of the UO2 matrix by these molecular oxidants, and that the kinetics of the catalyzed reactions is close to diffusion controlled.