Modeling liquid–gas iodine mass transfer under evaporative conditions during severe accidents

During postulated severe accidents transfer of volatile iodine dissolved in containment water sumps to atmosphere can be fostered under pool evaporative conditions. Scarcity of representative data has resulted in semi-empirical models that relies on fitting parameters and still need of further validation. This paper presents a mechanistic model based on: the two-film model, the heat-mass transfer analogy and the surface renewal theory. Comparison to data from the SISYPHE program, performed at the French “Institut de Radioprotection et de Sûreté Nucléaire”, has resulted in an accurate response, the error band being 9–25% for the aqueous steady state concentration. Likewise, the model performance has been compared to the model implemented in the ASTEC code. In addition to yield similar results, some advantages have been highlighted: the mechanistic nature, the estimates conservatism, and the thorough documentation of model grounds and assumptions.