The effect of high fluence neutron irradiation on the properties of a fine-grained isotropic nuclear graphite

Abstract

A fine-grained isotropic nuclear graphite (IG-110), manufactured from a petroleum coke, was irradiated to a total neutron dose of 3.8 × 10 26 n/m 2 or 25 displacements per atom (dpa) at 600°C in the high flux isotope reactor (HFIR) at Oak Ridge: National Laboratory (ORNL). The effect of irradiation and the influence of post-irradiation thermal annealing on the properties of the graphite were evaluated. Volume change turnaround was clearly observed at 15—20 dpa and the return to original volume ( ΔV V 0 = 0 ) can be estimated to occur at ∼ 30 dpa. Strength and elastic moduli of the irradiated graphite increased by a factor of 2–3, and maximums in the δ δ 0 , and E E o curves were at ∼20 dpa at 600°C. Recovery of volume, fracture strength and thermal conductivity by thermal annealing were found., and thermal conductivity returned to better than about 30% of the unirradiated value after 1200°C thermal annealing.