GRAPHITE OXIDATION UNDER IRRADIATION BY TRACES OF CO$sub 2$ IN A HIGH PRESSURE HELIUM CARRIER GAS. Project DRAGON

This paper reviews work on graphite corrosion by traces of carbon dioxide in helium under irradiation in the BR2 Reactor at C.E.N., Mol, Belgium. The experimental work was performed for Dragon Project by the Group d’Exploitation du Reacteur BR2, C.E.N., Mol. The experiments covered the temperature range 250-900 deg C, in fast neutron fluxes up to 5 x 10{sup 14} n/cm{sup 2} s and gamma fluxes up to 15 W/g. The observed corrosion rates were almost independent of temperature and carbon dioxide concentrations (>10 vpm). The rates being of the same order of magnitude as the rates of the thermal reaction at 1000 deg C and 10 vpm CO{sub 2}. Decomposition of the carbon dioxide, with the formation of oxygen and carbon monoxide, was observed; and the amounts of oxygen produced could account forthe observed graphite corrosion rates. Hydrogen, carbon monoxide and methane were found to inhibit both the decomposition of the carbon dioxide and the radiolytically induced corrosion of the graphite. It was established that the observed radiolytic effects are largely due to energy transfer from the helium. (auth)