XPS AND SEM STUDIES ON THE CORROSION OF UO_2 COINTAINING PLUTONIUM IN DEMINERALIZED AND CARBONATED WATER

摘要

An oxidation and dissolution study has been performed on UO_2 pellets containing ～10 and ～0.1 wt. % ~(238)Pu, ～10 wt. % ~(239)Pu and on undoped UO_2 to investigate the effects of radiolysis and composition on the corrosion behavior of spent fuel. The so-called alpha-doped UO_2 is used to simulate the alpha-radiation field of different types of commercial LWR spent fuel after different storage times. Leaching experiments in dcmineralized and carbonated water at room temperature under oxidizing conditions showed that relatively high amounts of ~(238)Pu were released. The leached surfaces were examined with X-ray Photoemission Spectroscopy (XPS), and the progressive surface oxidation was monitored. The oxidation of the U(IV) during the leaching experiments, in the materials doped with ~(238)Pu resulted in precipitation of U(VI) phases: enhanced formation of studtite for the strongest radiation field and shoepite at low radiation field was observed on the surface of the pellet . Essentially no precipitation of Pu-rich phases was directly observed. Leaching in carbonated water and characterization of UO_2 containing ~(239)Pu under the same experimental conditions were performed and the results compared to those for alpha-doped UO_2. The chemistry effects due to the presence of Pu in addition to alpha-radiolysis were investigated.