(309g) The Migration Law of Nuclides in Steam Reforming Reaction of Spent Radioactive Resins

The treatment of spent radioactive resins in the nuclear industry is important due to its great potential hazard to human beings and environments. The two keys during the disposal of the resins are volume reduction ratio and leaching resistance. Considering these two aspects, the steam reforming technology is a better method for resin disposal with high volume reduction ratio (>6) and radionuclides retention efficiency (>99.99%). During the reaction, nuclides are released when the spent resins are pyrolyzed into light hydrocarbons, sulfides, carbon oxides and a little residue at 650-750℃. Meanwhile, the nuclides are contacted with silicon-aluminum compounds and structure directing agents in the reactor to form specific mineral, which can immobilize the nuclides in its structure. The key to the reaction is that the nuclides are released efficiently from the spent resins with large volume, and then immobilized by minerals with small volume. Therefore, it is of great significance to study the migration law of nuclides to regulate the immobilization efficiency. In this work, the migration process of nuclides in the pyrolysis of resins under the steam reforming reaction conditions is investigated in the fixed bed reactor. The pyrolysis products obtained from different reaction times and temperatures are analyzed by SEM-EDX to observe the morphologies and nuclides distribution. The form of nuclides are studied by XRD, and the quantification of nuclides are obtained by ICP-MS. It is found that different migration paths of nuclides occur in different pyrolysis stages of resins, and a migration model is proposed to describe the phenomenon. Most of the nuclides are retained in the residue with the form of oxides and inorganic salts.

Keywords: Migration law; Nuclides; Steam reforming reaction