The Chemical Behavior of Fission Product Iodine in Light Water Reactor Accidents

Abstract
It is commonly assumed that the chemical form of fission product iodine that escapes from the core of a light water reactor under accident conditions is the elemental form. Experimental evidence is presented that indicates that this assumption is incorrect; instead, a metal iodide (probably cesium iodide) is the chemical form that escapes from the fuel. Moreover, since transport through the primary system necessarily occurs under chemically reducing conditions, a change in valence of the iodine is not possible until the oxidizing conditions characteristic of reactor containment buildings are encountered. However, it is also demonstrated that elemental iodine cannot be a dominant form if, as occurred at the Three Mile Island reactor, the iodide contacts water and is transported into the containment building in aqueous solution.