Diffusion coefficients of cesium in un-irradiated graphite and comparison with those obtained from in-pile experiments

Abstract

Abstract Diffusion coefficients of trace-level cesium in un-irradiated IG-110 graphite were determined by thin-source annealing experiments. Thus obtained values of the diffusion coefficients were larger by 3–4 orders of magnitude than in-pile values for the same brand graphite. Activation energies of the diffusion coefficients for the un-irradiated graphite were 112 and 95 kJ/mol for two series of the laboratory experiments, which are considerably lower than the in-pile value of 157 kJ/mol. An extended diffusion-trap model is proposed to explain the decreased diffusion coefficient and the increased activation energy for the in-pile diffusion, by considering the trapping effect of irradiation-induced lattice defects.