REPROCESSING NUCLEAR FUEL CONTAINING POLYMERS

Organic radiolysis generates enough hydrogen gas to question the safety of radioactive fuel transportation and long-term storage. A safety analysis points out the absolute necessity to get rid of all organic substances in nuclear fuel long-term storage. In the past decades, R and D activities have been producing quantities of rod fuel samples embedded in polymer resins for characterization purposes. Until recently, resin has not been removed from samples and today large sample quantities have to be reprocessed. The "STAR" nuclear facility at CEA Cadarache in France devoted to used fuel stabilization and conditioning, recently decided to implement in the hot cell a particular process to achieve the safety requirements. In order to define a versatile process, efficient for any kind of polymer, thermal treatment has been chosen over a chemical or mechanical process. The definition of this particular thermal treatment must take into account; the hot cell environment, the nuclear safety rules and the behavior of resins. A prototypic furnace has been built for study purposes and thermal cycle validation. Today, the thermal cycle has been defined in two phases as follow: First phase: pyrolysis is used to transform resin into residues and gases. A post gas treatment will be added to the furnace for total gas oxidation. Second phase: Air thermal treatment will achieve the complete residue oxidation and guarantee a hydrogen free product. The final equipment will be available in 2009 for testing and validation cycles with a radioactive free simulator before it is to be implemented in the hot cell in 2010.