Studies on the oxidation of organic iodine by beta radiation

The first experiments on the radiolytical oxidation of gaseous iodine by beta radiation were conducted with a new BESSEL (Beta irradiation vESSEL) test facility of VTT Technical Research Centre of Finland. The reaction chamber was made of glass and a source of beta radiation (P-32, activity 5 mCi) was placed at the bottom. The residence time of gaseous sample in the radiation field, the composition of gas flow and the temperature of the facility could be adjusted. In the experiments, gaseous methyl iodide (CH3I) was exposed to beta radiation in various mixtures of oxygen and nitrogen. The results of the experiments at 20 °C revealed that as an outcome of radiolytic oxidation the nucleation of particles took place. Their measured diameter was very small, approx. 10 to 50 nm, but a small fraction of particles had a diameter even higher than 100 nm. The formed particles seemed to react with the humidity of air and dissolve very rapidly. Since particles were highly water soluble and volatile, it was very difficult to analyse their properties with SEM-EDX. The only observed gaseous reaction product was carbon dioxide (CO2). It was detected when the residence time of gaseous sample inside the reaction chamber was 1 day or more.