Use of RBS to validate europium surface implantation as a marker for the corrosion study of zirconia

This study is related to the nuclear waste management and to the long-term behaviour of radionuclides in deep storage. The aim of this paper is to stu dy the corrosion of zirconium in deep storage. In order to simulate the inn er side of zircaloy cladding tubes, the zirconium samples were oxidised in air at 500 degrees C during 3 h. Two hundred keV-implanted europium ions we re used as marker to follow the evolution of the ZrO2-liquid interface. In a first step, air annealings were performed in the temperature range 850-95 0 degrees C. Diffusion profiles were measured using 3 MeV alpha-particles R utherford backscattering spectrometry (RBS) at each step of annealing. By e xtrapolation it is shown that at 300 degrees C the europium diffusion in Zr O2 is negligible. In a second step, the specimens were exposed to a basic s olution (pH 13.5) at 300 degrees C in autoclave under a 10(7) Pa pressure. By means of RBS, it was possible to deduce the fraction of dissolved ZrO2. it was shown that this dissolution is inhomogeneous. These results are conf irmed by scanning electron microscopy (SEM). (C) 2000 Elsevier Science B.V. All rights reserved.