Graphite was used as a neutron moderator and reflector material in more than 100 nuclear plants in the world. In France, UNGG (Natural Uranium - Graphite - Gas) reactors were operating from 1956 to 1994. The irradiated graphite wastes are estimated to be about 23,000 tons in France (250,000 tons in the world). Such wastes are contaminated by radioactive isotopes such as ~3H,~(36)Cl,~(14)C (about 1 ppm for ~(14)C, i.e. 106 the natural abundance). After the reactor dismantling, these low level - long lived graphite wastes are planned to be directly disposed in a near surface repository. An alternative could be a partial decontamination of graphite wastes to decrease their radiological inventory and thus to allow other repository options. An important European Programme (31 partners from 11 countries), named 'Carbowaste started in 2008. Its objective is treatment and disposal of irradiated graphite and other carbonaceous waste. A special attention is paid on the inventory of radionuclides, their localization in the graphite matrix, and the study of their migration during disposal or various chemical or physical pre-treatments. A work package is devoted to the characterization of virgin and irradiated graphite from shared samples. Our French teams focused on the study of the multiscale organisation of these samples. Our objective was to specify the effects of neutron irradiation and irradiation temperatures in the working reactor on the nuclear graphite organization. Such knowledge is required for waste management. Before their disposal, some scenarii involve now a first step of partial decontamination to decrease graphite radiological activity. Based on our up to date HRTEM study, the elimination of 14C from irradiated nuclear graphite can be envisaged. A possible way involving carboxygasification was proposed by Dr Jean-No?l ROUZAUD at the Carbon 2011 conference [1].
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