The chemistry of iodine in containment

Recent investigations of iodine behavior under radiolytic conditions have d emonstrated that kinetics, not thermodynamics, will govern iodine speciatio n and partitioning under conditions typical of those expected in a reactor containment during an accident. In the presence of radiation, iodine volati lity is orders of magnitude higher than that expected based on thermodynami c calculations. Kinetic studies have contributed extensively to the existin g database of iodine chemistry and have several implications for modeling i odine behavior for safety analyses. For example, as a result of these inves tigations, many uncertainties in the iodine database, such as those regardi ng thermal oxidation of iodine, which were formerly regarded as reactor saf ety issues, are now considered to be relatively unimportant. In contrast, p reviously unconsidered factors. such as the effect on aqueous chemistry of impurities originating from surfaces, are now recognized as playing major r oles in determining iodine volatility. An updated review of the existing li terature regarding iodine behavior is provided, with a focus on recent deve lopments. A critical evaluation of the data in the context of developing a model for iodine behavior under reactor accident conditions is also provide d.