Iodine chemical forms entering containment

Some of the iodine species (e. g. Csl) will condense on surfaces or will form aerosols in the reactor pressure vessel or during their residence time in the pipes and components of the primary system they can be transported together with the primary aerosols or deposited within the primary system, but in each case they may undergo further chemical reactions potentially leading to other, more volatile products. Other species such as elemental iodine h are transported in gaseous form inside the primary circuit after having reached the containment free volume, they may enter into a partition equilibrium between sump water and containment atmosphere. For this reason, it is of considerable interest to know the chemical forms of fission product iodine that can be generated within the primary circuit. 

In the following time interval, lasting from 1000 minutes to about 2 to 3 weeks, vapor-phase iodine will essentially consist of the species I2 produced by radiolysis and be partitioned between aqueous solution and the gas phase there will also be minor amounts of organic iodide in the vapor phase. Iodine will be present in aqueous solution in forms that are determined both by radiolysis and by pH in addition, a fraction of iodine will be deposited onto structural surfaces. During this time interval, the chemical forms of iodine are not expected to be closely related to the chemical forms that entered the containment from the reactor primary system, because of the iodine reactions that have occurred in the meantime. 

Airborne particulates typically contain increased concentrations of halogens near the ocean, in polluted areas, and in regions of volcanic activity. Fluoride concentrations are increased near aluminum and steel miUs and phosphate-fertilizer plants. Bromide concentrations were once increased near urban areas as aresult ofthe burning of gasoline additives (ethylene dibromlde, a lead scavenger), but environmental legislation has resulted in a decline of this chemical s utilization. The enrichment of iodine in marine air as compared to sea water has been attributed to concentration of the element in organic surface films. Iodine-enriched material then enters the atmosphere in the form of spray. 

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