LAUSR

Abstract The behavior of SIMFUEL (rare earth doped uranium dioxide containing noble metal particles) has been studied in bicarbonate/carbonate solutions (pH = 9.7) containing hydrogen peroxide, using a combination of electrochemical techniques, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and inductively-coupled plasma mass spectrometry (ICP-MS). The hydrogen peroxide was found to decompose to oxygen and water both homogeneously and heterogeneously, accompanied by a minimal amount of corrosion of UO2. Homogeneous decomposition proceeded via a peroxycarbonate (CO42-) intermediate while heterogeneous decomposition was catalyzed by the reversible U IV ⇌ U V redox transformation in a thin U 1 − 2 x IV U 2 x V O 2 + x surface layer. The rate of the heterogeneous decomposition reaction depended on whether UVI surface species ((UVIO2CO3)ads, UVIO3•yH2O) were allowed to accumulate on the surface, blocking access of hydrogen peroxide to the catalytic surface layer.