The effect of neutron irradiation on the reactor graphite corrosion kinetics

Abstract Investigations were carried out on the corrosion kinetics of initial and irradiated reflector and matrix graphites of several grades in helium flow containing various types of oxidants. The parameters of the sample irradiation were: the neutron fluence F = 1.5 × 10 21 −2.0 × 10 22 cm −2 ( E > 0.18 MeV ) and the irradiation temperature T = 350–1100° C . The investigations were made in the temperature interval T C over the concentration range of water vapor admixed to helium of 100–600 vpm, oxygen 350–6000 vpm and carbon dioxide 400–6000 vpm at an absolute total pressure of 1.32 bar. A qualitative change of the corrosion kinetics was found with the increase of the irradiation fluence of the samples. The increase in corrosion rate was explained by fracture of the graphite intercrystallite boundaries under irradiation and by increase in relative density of monocrystal surfaces opening into pores, normal to the basal plane.