Elastic recoil detection analysis, ERDA, with 2 MeV He ions was used to quantitatively measure hydration and hydrogen profiles in near-surface layers of UO2 for spent nuclear fuel direct storage and of SYNROC, a tailor-made titanate-based ceramic to incorporate radioactive waste for safe, long-term underground storage. No hydrogen uptake was observed at temperatures below 100 ° C, but for higher leaching temperatures up to 200 ° C and for longer times, hydrogen profiles could be measured for both materials for the first time. For the specific case of UO2, the combination of ERDA and of Rutherford backscattering analysis (combined with the channeling technique for UO2) enabled to measure the kinetics of UO2 leaching in water at elevated temperatures and pressures: a first oxidation of UO2 to U3O7 occurs with layer thicknesses of a fraction of a μm, followed by further oxidation to UO3 and simultaneous hydration as well as increases in layer thickness. Details of the technique and of the kinetics involved in hydration are presented. © 1990.
