Performance Assessment for Disposal of Irradiated Graphite From Research Reactors in a Near Surface Repository

The final disposal of irradiated graphite is a topical issue and urgently seeks for favourable solutions, but no firm decision has been taken so far concerning conditioning and packaging the graphitic waste although these materials impose major challenges due to big volumes and associated radionuclide inventory. In Romania, irradiated graphite does not exceed 10 tones and comes partly from the thermal column of the TRIGA reactor at INR Pitesti and partly from decommissioning of the VVSR reactor in Bucharest. The total radionuclide inventory is low and mainly dominated by ³H, ¹⁴C, ¹⁵²Eu, ⁶⁰Co and ³⁶Cl, depending on the position in the thermal column and irradiation history. However, an optimal solution for its final disposal is envisaged for the national radioactive waste management plan. An alternative may be disposal in a surface repository. ¹⁴C and ³⁶Cl are radioisotopes which may exhibit long term impact, both with potential to be released from graphitic material. In this context, the paper proposes a GoldSim model for the performance assessment of irradiated graphite disposal in a surface repository with characteristics borrowed from the Saligny site, considering only ¹⁴C and ³⁶Cl radioisotopes. As there are still a lot of uncertainties and a lack of some relevant input parameters, the model is rather a support on which adjustments are still to be made as soon as new data become available regarding this topic. (author).