Iodine release from oxidised Zircaloy cladding in contact with an alkaline solution

During reactor processing, fission products, among which iodine, are implanted by recoil inside the Zircaloy cladding tube. At the same time, oxidation of the cladding tube occurs, hence in the waste storage phase, zirconia acts as a migration barrier. Before chemical separation, the cladding tubes are sectioned into pieces called hulls in order to release the UO2 pellets which are rendered soluble in nitric acid. The hulls are collected as a solid waste and were embedded inside a concrete structure until 1995. In the perspective of geological storage, a great interest is given to iodine release processes in order to model and to extrapolate them to large time scales. In order to analyse the mechanisms involved in iodine migration, iodine atoms were introduced in Zircaloy oxidized samples by means of ion implantation. Corrosion tests were performed in order to simulate the impact of infiltrated water in the concrete disposal. Iodine release was measured by Rutherford backscattering spectroscopy. Processes responsible for iodine release are analysed.