ABSTRACT
This chapter presents a brief review on the radiolysis effect on chemical forms of iodine under the condition of nuclear reactor accidents especially in containments. Radioactive iodine is one of the most important fission products in relation to their release to environment in nuclear reactor accidents. The iodine species released from fuels will get into aqueous phase in containments according to accident scenario. Cesium iodide and hydrogen iodide are very soluble in water and dissociate almost completely in the aqueous phase, giving iodide ions. There have been some thermodynamical and kinetic approaches to understanding of chemical behavior of iodine in relation to nuclear reactor accidents. On the other hand, when iodine species are subject to radiation in the aqueous phase, the radiolysis has a possibility to give a large effect on the chemical form of the iodine species. This radiolytic effect is currently one of the great concerns in the source term problems of nuclear reactor accidents.
