Ion irradiation to simulate neutron irradiation in model graphites: Consequences for nuclear graphite

摘要: Due to its excellent moderator and reflector qualities, graphite was used in CO2-cooled nuclear reactors such as UNGG (Uranium Naturel-Graphite-Gaz). Neutron irradiation of resulted the production 14C which is a key issue radionuclide for management irradiated waste. In order elucidate impact neutron on behavior, we carried out systematic investigation synergistic effects with temperature Highly Oriented Pyrolitic Graphite (HOPG) model simulate coke grains graphite. We 13C implantation displaced from original structural site through recoil. The collision impinging neutrons matrix carbon atoms induces mainly ballistic damage. However, part recoil atom energy also transferred lattice electronic excitation. different regimes synergy were simulated using ion by varying Sn(nuclear)/Se(electronic) stopping power. Thus, samples ions energies. structure modifications followed High Resolution Transmission Electron Microscopy (HRTEM) Raman microspectrometry. results show that generally counteracts disordering but achieved reordering level strongly depends initial state matrix. extrapolating reactor conditions, an initially highly disordered structure, at temperatures (200 – 500 °C) should induce almost no change structure. On contrary, when less disordered, there be “zoning” reordering: “cold” high flux zones where damage important, poorly reordered; “hot” low lower can therefore counteracted temperature, better achieved. Concerning 14C, except located close open pores it removed radiolytic corrosion, tends stabilize into sp2 or sp3 structures variable proportions depending conditions.