Investigation of the behaviour of gaseous I2 and RuO4 in different atmospheres

Licentiate thesis, 2009

During a severe accident several hazardous and radiotoxic fission products can be released and constitute a threat to the environment. Two of the most important fission products are iodine and ruthenium which will be accumulated after inhalation in the human body in the thyroid gland and in the respiratory organs, respectively. Experiments in this work have been performed to study the behaviour of gaseous iodine and ruthenium species in different conditions. The reaction between iodine and the air radiolysis product ozone has been investigated in different atmospheres, i.e. various concentrations of nitrogen and oxygen gas. The interaction of gaseous ruthenium tetroxide and surfaces of aluminium, copper and zinc has been examined in different atmospheres, humid or dry nitrogen gas and air. When gaseous iodine and ozone were present simultaneously in the system, particle formation was started immediately after introduction of the gaseous species. The formed primary particles were about 10 nm in diameter and grown to about 100 nm in size, as a result of agglomeration of the particles. The formed particles were found to be some kind of iodine oxides, but the exact speciation was difficult to determine due to analysis problems. The deposition of gaseous ruthenium tetroxide was extensive on all the examined metal surfaces, but mainly on the copper and zinc surfaces. The surface analyses of the interacted metals showed that the speciation of the ruthenium deposits were mainly anhydrous or hydrous ruthenium dioxide, depending on the temperature conditions. The results in this work show that both airborne iodine and ruthenium may be depleted from the gaseous phase, through different interactions with other species in gaseous phase and surfaces in the containment.