[en] The following experiments were planned to look at the effects of water-droplets sizes and radiation field on the migration of volatile I₂ and CH₃I that may occur during an accident in the nuclear-reactor containment. 0, 38, 42, and 48 μm sizes of water droplets could be generated when 0, 80, 60, and 40 kHz frequencies were applied at a nominal operating condition (20 μm orifice diameter, 20 cm³ syringe capacity, 8.2 x 10-4 cm/s syringe pump run speed, and 0.139 cm³/min liquid feed rate). The formed monodisperse water droplets were well dispersed with 15 x 100 cm³/min air and diluted 40 L/min air before significant coagulation occurs. Gases of I₂ and CH₃I were generated at about 60.deg.C and room temperature respectively and then led to the cylindrical water jet with the volumetric flowrate of 5cc/min. The amount of transferred gaseous iodine by adsorption on water droplets was strongly influenced by the existence of water. CH₃I and H₂O can decompose into various chemical species on exposure to external radiation, so a transferred amount of CH₃I on water droplets were lower under the combination of 10 μCi Na-22, 1 μCi Cd-109, 1 μCi Cs-137, and 1 μCi Co-57 radioactive source discs than the case of absence of the radiation condition as shown in Figure 2. However, a relationship between the transferred volatile CH₃I concentrations and water droplet sizes showed the same trend to the case of absence of the radiation condition. Hydrolysis reaction rates of I₂ and CH₃I with water are very slow in comparison with physical weathering and physical dissolution, and they are only slightly soluble in water.