Thermodynamical Calculations on the Behavior of Gaseous Iodine Species Following a Hypothetical Severe Light Water Reactor Accident

Using the computer code SOLGASMIX-PV, thermodynamical equilibrium concentrations of the iodine species in the gaseous systems Ag-I-H-O and Ag-Cs-I-H-O were calculated under experimental conditions resembling those of hypothetical severe light water reactor accidents. These calculations indicate that in a temperature range up to 1800°C AgI would be a thermodynamically stable species, which suggests that silver, originating from the evaporation of the control rods, could act as a potential sink for fission iodine by converting it to water insoluble Agl. The efficiency of this process depends on the relative concentrations of silver and iodine and is subject to the kinetics involved.