Diffusion study of implanted iodine in zirconium using ion beams

This study is related to the back end of the nuclear fuel cycle. During nuc lear reactor operation, the inner side of the zircaloy cladding tube is imp lanted by recoil with fission products. Among them,I-129 poses a real probl em firstly, because it is a volatile element and secondly because it has a very long half-life (T = 1.59 x 10(7) years). The aim of this paper is to m ake an analysis of iodine diffusion into zirconium compared to zirconium ox ide. In order to analyse the mechanisms involved in iodine migration, stabl e (I-127) and radioactive iodine (I-131) species were implanted into zircon ium. Diffusion profiles of iodine were followed as a function of successive annealing times (up to several hours) and temperatures (in the range 400-6 00 degrees C), either by using Rutherford backscattering spectrometry to pr ofile I-127 Or by gamma spectroscopy to measure I-131 release. These two te chniques allowed us to determine very low iodine diffusion coefficient valu es (down to 10(-17) cm(2) s(-1)) and to extrapolate them to waste storage c onditions. (C) 2000 Elsevier Science S.A. All rights reserved.