Radioactive iodine removing method and device therefor

In a reprocessing facility for spent nuclear fuels, radioactive iodine is reacted with metal elements of tri-or higher valence and removed from a gas or a solution. This makes facilities for removing iodine in off gases in a fuel manufacturing step unnecessary, and radioactive iodine having a long half life is fixed at a high density as metal iodides. Compounds comprising metal elements and iodine are stable solids at within a range of from room temperature to 600degC. The metal elements which form stable iodine compounds even at a high temperature (several hundreds degC) prevent volatilization and scattering of iodine upon occurrence of fire during storage of fuels and materials to be transmuted or upon transmutation treatment. Metal elements which form iodide compounds having a compositional ratio of iodine to the metal element of 3 or more reduce the volume of iodine during storage and keep a high transmutation efficiency. (N.H.)