Migration chemistry and behaviour of iodine relevant to geological disposal of radioactive wastes - a literature review with a compilation of sorption data

This report reviews the literature on iodine migration, chemistry and behaviour in the environment up to November 1987. It deals mainly with 129I released from a land repository, with particular consideration of the Swiss scenario for the disposal of low- and medium-level radioactive waste. As a background to this review, the basic properties of radioiodine, its distribution, circulation in nature and radiological impact are presented. A large number of sorption and diffusion data for iodine on rocks, sediments, minerals, cements and other materials have been compiled from many different laboratories. Based on this information, an assessment of the sorption and retardation of radioiodine in geomedia is made and methodologies for obtaining sorption distribution ratios (RD values) are discussed. The review also covers natural analogue studies of 129I, retardation of iodine by cement barriers and the possible influences of organic compounds and microorganisms on the behaviour of iodine. Some possibilities for further research on diffusion measurements and near-field chemistry of radioiodine are outlined. (author) 259 refs., 9 figs., 30 tabs