Thermal Decontamination of FRJ-2 Irradiated Graphite: Selective Removal of γ-Emitting Radionuclides

A large quantity of irradiated nuclear graphite has been generated worldwide and must be managed as radioactive waste. In Germany, the final disposal of irradiated graphite (i-graphite) remains challenging due to limited knowledge of the radionuclide inventory and strict regulatory constraints. The presence of gamma-emitting radionuclides raises concerns regarding radiation exposure during handling, for example, in reactor decommissioning operations. Decontamination processes are therefore being investigated to enable the selective removal of key radionuclides, with the dual objective of facilitating waste acceptance and enabling the potential reuse of treated graphite in technical applications. This study focuses on the selective removal of volatile gamma-emitting radionuclides using a thermal treatment approach. In this work, a steam-assisted thermal treatment was applied to i-graphite samples from the Forschungsreaktor Jülich 2 (FRJ-2). The influence of key process parameters, including temperature, treatment duration, and relative humidity, was systematically investigated. The results show complete removal of 60Co and 137Cs, while partial removal of approximately 40% was achieved for 152,154,155Eu and 241Am. No release of 133Ba was observed. These findings demonstrate the potential of high-temperature treatment as an effective method for reducing the radionuclide inventory of irradiated graphite, thereby contributing to improved waste management strategies and safer handling during decommissioning.