STUDY OF IODINE MIGRATION IN ZIRCONIA USING STABLE AND RADIOACTIVE ION-IMPLANTATION

The large uranium fission cross section leading to iodine and the beha viour of this element in the cladding tube during energy production an d afterwards during waste storage is a crucial problem, especially for I-129 which is a very long half-life isotope (T = 1.59 x 10(7) yr). S ince a combined external and internal oxidation of the zircaloy claddi ng tube occurs during the reactor processing iodine diffusion paramete rs in zirconia are needed. In order to obtain these data, stable iodin e atoms were first introduced by ion implantation into zirconia with a n energy of 200 keV and a dose equal to 8 x 10(15) at cm(-2). Diffusio n profiles were measured using 3 MeV alpha-particle Rutherford Backsca ttering Spectrometry at each step of the annealing procedure between 7 00 degrees C and 900 degrees C. In such experiments a reduced iodine c oncentration was observed. which correlated to a diffusion-like proces s. Similar analysis has been performed using radioactive I-131 implant ed at a very low dose of 10(9) at cm(-2). In this case the iodine rele ase is deduced from gamma-ray spectroscopy measurements. The results a re discussed in this paper. (C) 1998 Elsevier Science B.V.