Analysis With ART Code for Adsorption of Molecular Iodine Onto Aerosols During Severe Accidents

Two tests performed in the THAI-2 project of the OECD/NEA on the adsorption of molecular iodine onto chemically inactive and active aerosols were analyzed with ART code for analysis of transportation of radioactive materials during a severe accident in order mainly to estimate adsorption velocities of I₂ onto the aerosols. The results of the analysis for aerosol characteristics including airborne concentration and size distribution were reasonably agreed with the measured tendencies. The total surface areas of the aerosols, contributing to physisorption and chemisorption of I₂, were evaluated to be comparable with the surface area of the THAI test vessel wall. It was found that, giving the adsorption velocity onto aerosol at 10⁻⁵ through 10⁻⁴ m/s, the decreasing tendency in the airborne concentration of I₂ was well reproduced for the test with chemically inactive aerosol. The present analysis also indicated that the adsorption velocity in the test with chemically active aerosol was estimated to be larger than that in the test with chemically inactive aerosol by two orders.